tag:theconversation.com,2011:/ca/topics/climate-modelling-1397/articlesClimate modelling – The Conversation2024-03-08T13:35:18Ztag:theconversation.com,2011:article/2251452024-03-08T13:35:18Z2024-03-08T13:35:18ZDune: what the climate of Arrakis can tell us about the hunt for habitable exoplanets<p>Frank Herbert’s Dune is epic sci-fi storytelling with an environmental message at its heart. The novels and movies are set on the desert planet of Arrakis, which various characters dream of transforming into a greener world – much like some envision for Mars today. </p>
<p>We investigated Arrakis using a <a href="https://theconversation.com/dune-we-simulated-the-desert-planet-of-arrakis-to-see-if-humans-could-survive-there-170181">climate model</a>, a computer program similar to those used to give weather forecasts. We found the world that Herbert had created, well before climate models even existed, was remarkably accurate – and would be habitable, if not hospitable.</p>
<p>However, Arrakis wasn’t always a desert. In Dune lore, 91% of the planet was once covered by oceans, until some ancient catastrophe led to its desertification. What water remained was further removed by sand trout, an invasive species brought to Arrakis. These proliferated and carried liquid into cavities deep underground, leading to the planet becoming more and more arid.</p>
<p>To see what a large ocean would mean for the planet’s climate and habitability, we have now used the same climate model – putting in an ocean while changing no other factors. </p>
<p>When most of Arrakis is flooded, we calculate that the global average temperature would be reduced by 4°C. This is mostly because oceans add moisture to the atmosphere, which leads to more snow and certain types of cloud, both of which reflect the sun’s energy back into space. But it’s also because oceans on Earth and (we assume) on Arrakis emit “halogens” that <a href="https://www.nature.com/articles/s41586-023-06119-z">cool the planet</a> by depleting ozone, a potent greenhouse gas which Arrakis would have significantly more of than Earth.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/580451/original/file-20240307-18-5829gu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Map of Arrakis" src="https://images.theconversation.com/files/580451/original/file-20240307-18-5829gu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/580451/original/file-20240307-18-5829gu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=207&fit=crop&dpr=1 600w, https://images.theconversation.com/files/580451/original/file-20240307-18-5829gu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=207&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/580451/original/file-20240307-18-5829gu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=207&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/580451/original/file-20240307-18-5829gu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=261&fit=crop&dpr=1 754w, https://images.theconversation.com/files/580451/original/file-20240307-18-5829gu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=261&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/580451/original/file-20240307-18-5829gu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=261&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The authors gathered information from the books and the Dune Encyclopedia to build their original model. Then they added an ocean with 1,000 metres average depth.</span>
<span class="attribution"><span class="source">Farnsworth et al</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
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<p>Unsurprisingly, the ocean world is a whopping 86 times wetter, as so much water evaporates from the oceans. This means plants can grow as water is no longer a finite resource, as it is on desert Arrakis.</p>
<h2>A wetter world would be more stable</h2>
<p>Oceans also reduce temperature extremes, as water heats and cools more slowly than land. (This is one reason Britain, surrounded by oceans, has relatively mild winters and summers, while places far inland tend to be <a href="https://weatherspy.net/?city=London&city=Winnipeg&metric=1">hotter in summer and very cold in winter</a>). The climate of an ocean planet is therefore more stable than a desert world. </p>
<p>In desert Arrakis, temperatures would reach 70°C or more, while in its ocean state, we put the highest recorded temperatures at about 45°C. That means the ocean Arrakis would be liveable even in summer. Forests and arable crops could grow outside of the (still cold and snowy) poles. </p>
<p>There is one downside, however. Tropical regions would be buffeted by large cyclones since the huge, warm oceans would contain lots of the energy and moisture required to drive hurricanes.</p>
<h2>The search for habitable planets</h2>
<p>All this isn’t an entirely abstract exercise, as scientists searching for habitable “exoplanets” in distant galaxies are looking for these sorts of things too. At the moment, we can only detect such planets using huge telescopes in space to search for those that are similar to Earth in size, temperature, available energy, ability to host water, and other factors. </p>
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<a href="https://images.theconversation.com/files/580454/original/file-20240307-28-l1ov3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Scatter chart of planets comparing habitability and similarity to Earth." src="https://images.theconversation.com/files/580454/original/file-20240307-28-l1ov3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/580454/original/file-20240307-28-l1ov3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=482&fit=crop&dpr=1 600w, https://images.theconversation.com/files/580454/original/file-20240307-28-l1ov3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=482&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/580454/original/file-20240307-28-l1ov3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=482&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/580454/original/file-20240307-28-l1ov3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=606&fit=crop&dpr=1 754w, https://images.theconversation.com/files/580454/original/file-20240307-28-l1ov3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=606&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/580454/original/file-20240307-28-l1ov3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=606&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Both desert and ocean Arrakis are considerably more habitable than any other planet we have discovered.</span>
<span class="attribution"><span class="source">Farnsworth et al</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>We know that desert worlds are probably more common than Earth-like planets in the universe. Planets with potentially life-sustaining oceans will usually be found in the so-called “Goldilocks zone”: far enough from the Sun to avoid being too hot (so further away than boiling hot Venus), but close enough to avoid everything being frozen (so nearer than Jupiter’s icy moon Ganymede). </p>
<p>Research has found this habitable zone is particularly <a href="https://www.liebertpub.com/doi/10.1089/ast.2010.0545">small for planets with large oceans</a>. Their water is at risk of either completely freezing, therefore making the planet even colder, or of evaporating as part of a runaway greenhouse effect in which a layer of water vapour prevents heat from escaping and the planet gets hotter and hotter. </p>
<p>The habitable zone is therefore much larger for desert planets, since at the outer edge they will have less snow and ice cover and will absorb more of their sun’s heat, while at the inner edge there is less water vapour and so less risk of a runaway greenhouse effect.</p>
<p>It’s also important to note that, though distance from their local star can give a general average temperature for a planet, such an average can be misleading. For instance, both desert and ocean Arrakis have a habitable average temperature, but the day-to-day temperature extremes on the ocean planet are much more hospitable. </p>
<p>Currently, even the most powerful telescopes cannot sense temperatures at this detail. They also cannot see in detail how the continents are arranged on distant planets. This again could mean the averages are misleading. For instance, while the ocean Arrakis we modelled would be very habitable, most of the land is in the polar regions which are under snow year-round – so the actual amount of inhabitable land is much less. </p>
<p>Such considerations could be important in our own far-future, when the Earth is projected to form a <a href="https://www.nature.com/articles/s41561-023-01259-3">supercontinent centred on the equator</a>. That continent would make the planet far too hot for mammals and other life to survive, potentially leading to mass extinction.</p>
<p>If the most likely liveable planets in the universe are deserts, they may well be very extreme environments that require significant technological solutions and resources to enable life – desert worlds will probably not have an oxygen-rich atmosphere, for instance.</p>
<p>But that won’t stop humans from trying. For instance, Elon Musk and SpaceX have grand ambitions to <a href="https://www.nytimes.com/2023/10/05/science/elon-musk-spacex-starship-mars.html">create a colony</a> on our closest desert world, Mars. But the many challenges they will face only emphasises how important our own Earth is as the cradle of civilisation – especially as ocean-rich worlds may not be as plentiful as we’d hope. If humans eventually colonise other worlds, they’re likely to have to deal with many of the same problems as the characters in Dune.</p>
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<img alt="Imagine weekly climate newsletter" src="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p class="fine-print"><em><span>Alex Farnsworth works for the University of Bristol and receives funding from NERC and the Chinese Academy of Sciences.</span></em></p><p class="fine-print"><em><span>Sebastian Steinig works for the University of Bristol and receives funding from NERC.</span></em></p><p class="fine-print"><em><span>Michael Farnsworth does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Climate scientists have simulated Arrakis as a desert and with its long-lost oceans.Alex Farnsworth, Senior Research Associate in Meteorology, University of BristolMichael Farnsworth, Research Lead Future Electrical Machines Manufacturing Hub, University of SheffieldSebastian Steinig, Research Associate in Paleoclimate Modelling, University of BristolLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2210042024-01-17T02:38:02Z2024-01-17T02:38:02ZUp to 5 billion people to be hit by rainfall changes this century if CO₂ emissions are not curbed, research shows<p>Three to five billion people – or up to two-thirds of the world’s population – are set to be affected by projected rainfall changes by the end of the century unless the world rapidly ramps up emissions reduction efforts, according to <a href="https://www.nature.com/articles/s41467-023-44513-3">new research</a> by myself and colleagues.</p>
<p>To date, the effects of climate change on global rainfall has been <a href="https://www.carbonbrief.org/explainer-what-climate-models-tell-us-about-future-rainfall/">uncertain</a>. This has hampered our capacity to adapt to climate change and prepare for natural disasters.</p>
<p>Our method overcomes this uncertainty. We identified the regions where multiple climate models make similar projections about future rainfall impacts, and so reveal the global hot spots for drier and wetter conditions in future. </p>
<p>Our findings have deep implications for a large proportion of the world’s population – including millions of Australians.</p>
<figure class="align-center ">
<img alt="girl in pink dress plays in muddy puddle" src="https://images.theconversation.com/files/569712/original/file-20240117-27-tng0ok.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/569712/original/file-20240117-27-tng0ok.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/569712/original/file-20240117-27-tng0ok.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/569712/original/file-20240117-27-tng0ok.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/569712/original/file-20240117-27-tng0ok.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/569712/original/file-20240117-27-tng0ok.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/569712/original/file-20240117-27-tng0ok.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Up to five billion people, including millions of Australians, are set to be affected by rainfall changes by 2100 under climate change.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>Navigating the uncertainty of rain projections</h2>
<p>Climate models are one of the main ways scientists understand how the climate behaved in the past and might change in future. They <a href="https://theconversation.com/yes-a-few-climate-models-give-unexpected-predictions-but-the-technology-remains-a-powerful-tool-165611">comprise</a> millions of lines of computer code and use mathematical equations to <a href="https://www.climate.gov/maps-data/climate-data-primer/predicting-climate/climate-models">represent</a> how energy and materials move through the ocean, atmosphere and land. For future projections, climate models are driven by <a href="https://www.carbonbrief.org/explainer-how-shared-socioeconomic-pathways-explore-future-climate-change/">emissions scenarios</a> representing various possible emissions trajectories.</p>
<p>Using climate models to simulate future rainfall patterns is a difficult task. Rain is influenced by complex factors, such as radiative balance (how much of the Sun’s energy is coming in versus how much is leaving), as well as climate drivers linked to specific sea surface temperature patterns, such as El Niño and La Niña. This means different climate models often produce different rainfall projections, especially at a regional level.</p>
<p>We wanted to investigate the extent to which climate models “agree”, or produce similar projections, about how CO₂ emissions may affect future rainfall around the globe.</p>
<p>There are several ways to do this. The usual method is to average out data collected over time – say, two decades. But this approach can eliminate important information and obscure vital insights into how rainfall will behave in future.</p>
<p>We used an innovative and more comprehensive approach based on “time-series” data, or data collected at regular intervals over time – comprising historical and future projections from 1980 to 2100. This approach accounts for continual changes over time, both in the recent past and out to the end of this century.</p>
<p>We analysed both the <a href="https://wcrp-cmip.org/cmip-phase-6-cmip6/">current</a> and <a href="https://wcrp-cmip.org/cmip-phase-5-cmip5/">previous</a> generations of climate models – 146 in all.</p>
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Read more:
<a href="https://theconversation.com/yes-a-few-climate-models-give-unexpected-predictions-but-the-technology-remains-a-powerful-tool-165611">Yes, a few climate models give unexpected predictions – but the technology remains a powerful tool</a>
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<h2>The global hotspots</h2>
<p>Our analysis showed several countries facing drier conditions in future. The top five most affected were Greece, Spain, Palestine, Portugal and Morocco, where at least 85% of models projected significantly reduced annual rainfall by the end of this century, under a worst-case scenario of very high emissions.</p>
<p>In contrast, for Finland, North Korea, Russia, Canada and Norway, more than 90% of models agreed on a trend towards increasing annual rainfall.</p>
<p>The picture was similar for most parts of the highly populated nations of China and India, which are together home to more than 2.7 billion people. In those nations, 70% of models agreed on projections for increasing rainfall.</p>
<p>Our analysis showed some European countries, including the United Kingdom, Germany and France, were generally projected to experience less rainfall in summer and more in winter. These increases and decreases offset each other, which means no change in total rainfall, but substantial changes in seasonal distributions over the year.</p>
<p>Using our approach, rainfall projections remained unclear for some parts of the world. These include most of Australia, as well as central Europe, southwest Asia and parts of the African west coast and South America. </p>
<p>All up, the regions getting wetter or drier under global warming cover a vast proportion of the globe. Under scenarios where emissions remain intermediate (where emissions decline to about half of 2050 levels by the end of the century), 38% of the current world’s population, or three billion people, would be affected by changes in rainfall.</p>
<p>If we experience very high emissions instead, 66% of the world’s population – or five billion people – would be affected. Many of these regions are already experiencing the <a href="https://theconversation.com/how-climate-change-intensifies-the-water-cycle-fueling-extreme-rainfall-and-flooding-the-northeast-deluge-was-just-the-latest-209476">wetting</a> and <a href="https://theconversation.com/drought-in-the-amazon-understanding-the-causes-and-the-need-for-an-immediate-action-plan-to-save-the-biome-215650">drying</a> effects of climate change. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/569240/original/file-20240115-25-6zr8br.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/569240/original/file-20240115-25-6zr8br.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/569240/original/file-20240115-25-6zr8br.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=559&fit=crop&dpr=1 600w, https://images.theconversation.com/files/569240/original/file-20240115-25-6zr8br.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=559&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/569240/original/file-20240115-25-6zr8br.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=559&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/569240/original/file-20240115-25-6zr8br.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=702&fit=crop&dpr=1 754w, https://images.theconversation.com/files/569240/original/file-20240115-25-6zr8br.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=702&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/569240/original/file-20240115-25-6zr8br.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=702&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Regions where global models agree most on projected future wetter and drier conditions under intermediate and very high emissions. Bar charts show countries ranked by model agreement with lines displaying internal variability.</span>
<span class="attribution"><span class="source">Author provided</span></span>
</figcaption>
</figure>
<h2>A spotlight on Australia</h2>
<p>Our analysis for Australia found climate models agree on a significant drying hotspot over the Indian Ocean, engulfing Australia’s southwestern and south coasts. Spring was the season with the greatest rainfall reduction over this region. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/569247/original/file-20240115-25-b6hxs5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/569247/original/file-20240115-25-b6hxs5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/569247/original/file-20240115-25-b6hxs5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=320&fit=crop&dpr=1 600w, https://images.theconversation.com/files/569247/original/file-20240115-25-b6hxs5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=320&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/569247/original/file-20240115-25-b6hxs5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=320&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/569247/original/file-20240115-25-b6hxs5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=402&fit=crop&dpr=1 754w, https://images.theconversation.com/files/569247/original/file-20240115-25-b6hxs5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=402&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/569247/original/file-20240115-25-b6hxs5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=402&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Red and blue regions show locations where drying and wetting was detected by multiple climate models</span>
<span class="attribution"><span class="source">Author provided</span></span>
</figcaption>
</figure>
<p>What about at a state level? Under a very high emissions scenario, half of models indicate future drier conditions for Victoria. This is driven by changes in winter and spring rainfall. Other states and territories with agreement for a drier future winter, also under a high emissions scenario, include the Australian Capital Territory and Western Australia. The models also project a reduction in spring rainfall in Tasmania.</p>
<p>Some 1.9 million Australians would be affected by these drying patterns, under an intermediate emissions scenario. They comprise those in southwest WA including Perth and the Wheatbelt region. Under very high emissions, as the impacted region expands fourfold towards western Victoria, around 8 million Australians could be affected.</p>
<figure class="align-center ">
<img alt="Australasian regions where most global models agree on future drier and wetter patterns under elevated emissions" src="https://images.theconversation.com/files/569245/original/file-20240115-27-xmcyka.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/569245/original/file-20240115-27-xmcyka.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=424&fit=crop&dpr=1 600w, https://images.theconversation.com/files/569245/original/file-20240115-27-xmcyka.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=424&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/569245/original/file-20240115-27-xmcyka.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=424&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/569245/original/file-20240115-27-xmcyka.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=533&fit=crop&dpr=1 754w, https://images.theconversation.com/files/569245/original/file-20240115-27-xmcyka.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=533&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/569245/original/file-20240115-27-xmcyka.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=533&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Australasian regions where most global models agree on future drier and wetter patterns under elevated emissions. Southwestern Australia and parts of the south and east coasts may experience a drier future under very high emissions (shaded red). When moderate emissions are considered, the affected region is reduced (red contours).</span>
<span class="attribution"><span class="source">Author provided</span></span>
</figcaption>
</figure>
<h2>Looking ahead</h2>
<p>As climate change accelerates, it’s essential to understand the potential changes in global rainfall and the consequences on human populations.</p>
<p>My colleagues and I hope our findings reduce uncertainty about how rainfall patterns will shift around the world, and help governments and communities to design effective ways to adapt.</p><img src="https://counter.theconversation.com/content/221004/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ralph Trancoso leads the Queensland Future Climate Science Program - a collaborative program between the University of Queensland and Queensland's Department of Environment and Science undertaking applied climate science to support climate adaptation and natural disaster preparedness.</span></em></p>To date, the effects of climate change on global rainfall has been uncertain. New research overcomes this uncertainty – with alarming results.Ralph Trancoso, Adjunct Associate Professor in Climate Change, The University of QueenslandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2204582024-01-08T16:08:22Z2024-01-08T16:08:22ZGigantic solar farms of the future might impact how much solar power can be generated on the other side of the world<figure><img src="https://images.theconversation.com/files/568232/original/file-20240108-29-1u9uxi.jpg?ixlib=rb-1.1.0&rect=7%2C0%2C5283%2C3530&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/aerial-view-landscape-photovoltaic-solar-panel-1746395420">Kertu / shutterstock</a></span></figcaption></figure><p>The Sun’s energy is effectively limitless. While resources such as coal or gas are finite, if you are able to capture and use solar power it doesn’t prevent anyone else from also using as much sunshine as they need. </p>
<p>Except that isn’t quite the full story. Beyond a certain size, solar farms become large enough to affect the weather around them and ultimately the climate as a whole. In our <a href="https://www.nature.com/articles/s43247-023-01117-5">new research</a> we have looked at the effect such climate-altering solar farms might have on solar power production elsewhere in the world.</p>
<p>We know that solar power is affected by weather conditions and output varies through the days and seasons. Clouds, rain, snow and fog can all block sunlight from reaching solar panels. On a cloudy day, output can <a href="https://www.sciencedirect.com/science/article/abs/pii/S0038092X04002373">drop by 75%</a>, while their efficiency also decreases at high temperatures.</p>
<p>In the long term, climate change could affect the cloud cover of certain regions and how much solar power they can generate. Northern Europe is likely to see a solar <a href="https://www.nature.com/articles/ncomms10014">decrease</a> for instance, while there should be a slight increase of available solar radiation in the rest of Europe, the <a href="https://www.nature.com/articles/s41558-020-00949-9">US east coast</a> and <a href="https://academic.oup.com/nsr/article/10/1/nwac242/6780217">northern China</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/568234/original/file-20240108-17-b2hyqy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="clouds above solar panels" src="https://images.theconversation.com/files/568234/original/file-20240108-17-b2hyqy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/568234/original/file-20240108-17-b2hyqy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/568234/original/file-20240108-17-b2hyqy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/568234/original/file-20240108-17-b2hyqy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/568234/original/file-20240108-17-b2hyqy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/568234/original/file-20240108-17-b2hyqy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/568234/original/file-20240108-17-b2hyqy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Cloudy weather means less solar energy.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/solar-panel-farm-near-moonta-sa-2145570685">myphotobank.com.au / shutterstock</a></span>
</figcaption>
</figure>
<p>If we were ever to build truly giant solar farms, spanning whole countries and continents, they may have a similar impact. In our recent study, we used a <a href="https://ec-earth.org/">computer program</a> to model the Earth system and simulate how hypothetical enormous solar farms covering 20% of the Sahara would affect solar power generation around the world.</p>
<p>A photovoltaic (PV) solar panel is dark-coloured and so absorbs much more heat than reflective desert sand. Although a fraction of the energy is converted to electricity, much of it still heats up the panel. And when you have millions of these panels grouped together, the whole area warms up. If those solar panels were in the Sahara, our simulations show this new heat source would <a href="https://theconversation.com/solar-panels-in-sahara-could-boost-renewable-energy-but-damage-the-global-climate-heres-why-153992">rearrange global climate patterns</a>, shifting rainfall away from the tropics and leading to the desert becoming greener again, much as it was just 5,000 or so years ago. </p>
<p>This would in turn affect patterns of cloud cover and how much solar energy could be generated around the world. Regions that would become cloudier and less able to generate solar power include the Middle East, southern Europe, India, eastern China, Australia, and the US south-west. Areas that would generate more solar include Central and South America, the Caribbean, central and eastern US, Scandinavia and South Africa.</p>
<p><strong>How global solar potential would be affected:</strong></p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/568225/original/file-20240108-27-cerj7a.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Annotated world maps." src="https://images.theconversation.com/files/568225/original/file-20240108-27-cerj7a.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/568225/original/file-20240108-27-cerj7a.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=87&fit=crop&dpr=1 600w, https://images.theconversation.com/files/568225/original/file-20240108-27-cerj7a.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=87&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/568225/original/file-20240108-27-cerj7a.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=87&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/568225/original/file-20240108-27-cerj7a.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=109&fit=crop&dpr=1 754w, https://images.theconversation.com/files/568225/original/file-20240108-27-cerj7a.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=109&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/568225/original/file-20240108-27-cerj7a.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=109&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Map of changes in solar potential in the Sahara simulation. Changes to annual mean (left), December-January-February mean (centre), and June-July-August mean (right).</span>
<span class="attribution"><a class="source" href="https://www.nature.com/articles/s43247-023-01117-5">Long & Lu et al (2024)</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Something similar happened when we simulated the effects of huge solar farms in other hotspots in Central Asia, Australia, south-western US and north-western China – each led to climate changes elsewhere. For instance, huge solar farms covering much of the Australian outback would make it sunnier in South Africa, but cloudier in the UK, particularly during summer.</p>
<p><strong>If huge solar farms were installed in other drylands:</strong></p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/568229/original/file-20240108-19-2x33ok.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Annotated world maps" src="https://images.theconversation.com/files/568229/original/file-20240108-19-2x33ok.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/568229/original/file-20240108-19-2x33ok.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=237&fit=crop&dpr=1 600w, https://images.theconversation.com/files/568229/original/file-20240108-19-2x33ok.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=237&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/568229/original/file-20240108-19-2x33ok.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=237&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/568229/original/file-20240108-19-2x33ok.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=298&fit=crop&dpr=1 754w, https://images.theconversation.com/files/568229/original/file-20240108-19-2x33ok.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=298&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/568229/original/file-20240108-19-2x33ok.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=298&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Changes in solar potential annually (top panels), in december-january-february (middle panel), and june-july-august (bottom panel) in four scenarios where huge solar farms were constructed. The solar farms in Central Asia, Central Australia and Southwestern USA, Northwestern China are shown by purple polygons.</span>
<span class="attribution"><a class="source" href="https://www.nature.com/articles/s43247-023-01117-5">Long & Lu (2024)</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>There are some caveats. Things would only shift by a few per cent at most – however much solar power we build Scandinavia will still be cool and cloudy, Australia still hot and sunny. </p>
<p>And in any case, these effects are based on hypothetical scenarios. Our Sahara scenario was based on covering 20% of the entire desert in PV solar farms, for instance, and though there have been <a href="https://theconversation.com/should-we-turn-the-sahara-desert-into-a-huge-solar-farm-114450">ambitious proposals</a>, anything on that scale is unlikely to happen in the near future. If the covered area is reduced to a more plausible (though still unlikely) 5% of the Sahara, the global effects become mostly negligible. </p>
<h2>Why this thought experiment matters</h2>
<p>But in a future world in which almost every region invests in more solar projects and becomes more reliant on them, the interplay of solar energy resources can potentially shape the energy landscape, creating a complex web of dependencies, rivalries and opportunities. Geopolitical manoeuvring of solar project construction by certain nations may hold significant new power influencing solar generation potential far across their national boundaries.</p>
<p>That’s why it is essential to foster collaboration among nations to ensure that the benefits of solar energy are shared equitably around the world. By sharing knowledge and working together on the spatial planning of future large-scale solar projects, nations should develop and implement fair and sustainable energy solutions and avoid any unintended risks to solar power production far away.</p>
<hr>
<figure class="align-right ">
<img alt="Imagine weekly climate newsletter" src="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
</figcaption>
</figure>
<p><strong><em>Don’t have time to read about climate change as much as you’d like?</em></strong>
<br><em><a href="https://theconversation.com/uk/newsletters/imagine-57?utm_source=TCUK&utm_medium=linkback&utm_campaign=Imagine&utm_content=DontHaveTimeTop">Get a weekly roundup in your inbox instead.</a> Every Wednesday, The Conversation’s environment editor writes Imagine, a short email that goes a little deeper into just one climate issue. <a href="https://theconversation.com/uk/newsletters/imagine-57?utm_source=TCUK&utm_medium=linkback&utm_campaign=Imagine&utm_content=DontHaveTimeBottom">Join the 30,000+ readers who’ve subscribed so far.</a></em></p>
<hr><img src="https://counter.theconversation.com/content/220458/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Zhengyao Lu receives funding from FORMAS, the Crafoord Foundation, and the Swedish Research Council.</span></em></p><p class="fine-print"><em><span>Jingchao Long receives funding from the National Natural Science Foundation of China, The key construction discipline of high-level universities-Marine science, and GSTOEW.</span></em></p>Solar farms that span whole countries could change the climate – new study.Zhengyao Lu, Researcher in Physical Geography, Lund UniversityJingchao Long, Associate Professor, Department of Atmospheric Science, Guangdong Ocean UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2143612023-12-04T22:49:02Z2023-12-04T22:49:02ZWhat happens after net zero? The impacts will play out for decades, with poorest countries still feeling the heat<p>Humanity’s emissions of greenhouse gases have caused rapid <a href="https://www.ipcc.ch/report/ar6/syr/resources/spm-headline-statements/">global warming</a> at a rate unprecedented in at least the past 2,000 years. Rapid global warming has been accompanied by increases in the frequency and intensity of heat extremes over most land regions in the past 70 years. </p>
<p>While human activities cause emissions of a number of greenhouse gases, carbon dioxide (CO₂) stands out as the leading culprit. This is because of its relatively long atmospheric lifetime and because human activities cause much <a href="https://www.epa.gov/ghgemissions/global-greenhouse-gas-emissions-data">higher emissions of CO₂</a> than other greenhouse gases. </p>
<p>To avoid reaching unsafe global temperatures, <a href="https://www.ipcc.ch/sr15/chapter/spm/">climate scientists have concluded</a> we can’t prevent continued global warming without reaching a state of net zero CO₂ emissions.</p>
<p>But how might climate extremes change after net zero CO₂? There is limited research on this. Our new study, <a href="https://iopscience.iop.org/article/10.1088/1748-9326/ad114a">published in Environmental Research Letters</a>, uses a collection of models to address this gap. We found temperatures would respond very differently in various parts of the world, and heat extremes might continue to disproportionately affect vulnerable populations.</p>
<h2>The greenhouse effect and net zero emissions</h2>
<p>The world’s land and oceans have taken up most of the carbon humanity has emitted over the past six decades. However, land and oceans are incapable of absorbing 100% of CO₂ emissions.</p>
<p>The remaining CO₂ emissions over the past 60 years have been absorbed by the atmosphere, leading to an enhanced <a href="https://climate.nasa.gov/faq/19/what-is-the-greenhouse-effect/">greenhouse effect</a>. This has caused the especially rapid warming we’ve observed in the recent past. </p>
<p>To stop the continued enhancement of the greenhouse effect, we need to reach <a href="https://netzeroclimate.org/what-is-net-zero-2/">net zero</a> CO₂ emissions. Achieving net zero means reaching an overall balance between the CO₂ emissions humans produce and the CO₂ humans remove from the atmosphere.</p>
<p>The urgency of reaching net zero CO₂ emissions has sparked the use of state-of-the-art climate modelling techniques to answer the question – how does our climate change after net zero?</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-could-australia-actually-get-to-net-zero-heres-how-217778">How could Australia actually get to net zero? Here's how</a>
</strong>
</em>
</p>
<hr>
<h2>What lies beyond net zero CO₂?</h2>
<p>To try and answer this question, we used climate simulation models with increasing carbon dioxide in the atmosphere. Then, CO₂ emissions are “turned off” and simulations continue for 100 years more. This simple experimental setup allows us to compare the climate before net zero to climate patterns we might see after a transition to net zero.</p>
<p>There are regions where projected climate change patterns after net zero CO₂ are very uncertain. However, we saw several strong patterns:</p>
<ol>
<li><p>land cools after net zero CO₂ is achieved, while the ocean takes a bit more time to respond with some areas cooling and others warming;</p></li>
<li><p>the Southern Ocean continues to warm after net zero CO₂;</p></li>
<li><p>global temperature change (-0.23°C) is not always a good representation of regional temperature changes.</p></li>
</ol>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/550256/original/file-20230926-19-9hsjoz.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/550256/original/file-20230926-19-9hsjoz.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/550256/original/file-20230926-19-9hsjoz.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=366&fit=crop&dpr=1 600w, https://images.theconversation.com/files/550256/original/file-20230926-19-9hsjoz.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=366&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/550256/original/file-20230926-19-9hsjoz.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=366&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/550256/original/file-20230926-19-9hsjoz.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=460&fit=crop&dpr=1 754w, https://images.theconversation.com/files/550256/original/file-20230926-19-9hsjoz.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=460&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/550256/original/file-20230926-19-9hsjoz.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=460&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Change in regional temperature after net zero carbon dioxide emissions. Cross-hatching indicates areas where we are confident that regional temperatures increase (red hues) or decrease (blue hues).</span>
<span class="attribution"><span class="source">Author provided</span></span>
</figcaption>
</figure>
<h2>Heat extreme patterns after net zero CO₂</h2>
<p>Currently, less economically developed regions experience <a href="https://www.ipcc.ch/report/ar6/wg2/chapter/chapter-8/">disproportionate loss and damage</a> from climate extremes. Should we expect this to persist after net zero CO₂ emissions, or will the inequality of climate change be resolved by net zero? </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/cop28-climate-summit-just-approved-a-loss-and-damage-fund-what-does-this-mean-218999">COP28 climate summit just approved a 'loss and damage' fund. What does this mean?</a>
</strong>
</em>
</p>
<hr>
<p>We explored this issue by investigating if there are any changes in how often local heat extremes occur 100 years after net zero compared to how often they occur before net zero.</p>
<p>We then compared our results to maps of the <a href="https://hdr.undp.org/data-center/human-development-index#/indicies/HDI">Human Development Index</a> – a measure of socioeconomic development where regions with a high rank have higher incomes, more access to education and longer life expectancy. Other similar development indicators include <a href="https://hdr.undp.org/content/2023-global-multidimensional-poverty-index-mpi#/indicies/MPI">the Multidimensional Poverty Index</a>.</p>
<p>Although there are widespread decreases in how often heat extremes occur after net zero CO₂ emissions, regions with a relatively higher human development index such as North America and western Europe experience larger reductions in heat extremes than regions with a lower rank, such as Sub-Saharan Africa and southeast Asia.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/550260/original/file-20230926-25-uifg91.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/550260/original/file-20230926-25-uifg91.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/550260/original/file-20230926-25-uifg91.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=838&fit=crop&dpr=1 600w, https://images.theconversation.com/files/550260/original/file-20230926-25-uifg91.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=838&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/550260/original/file-20230926-25-uifg91.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=838&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/550260/original/file-20230926-25-uifg91.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1053&fit=crop&dpr=1 754w, https://images.theconversation.com/files/550260/original/file-20230926-25-uifg91.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1053&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/550260/original/file-20230926-25-uifg91.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1053&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Top: change in how often heat extremes occur regionally after net zero. Cross-hatching indicates areas where we are confident that heat extremes become more frequent (green hues) or less frequent (purple hues). Bottom: human development index in 2015.</span>
<span class="attribution"><span class="source">Author provided</span></span>
</figcaption>
</figure>
<h2>Preparing for a post net zero world</h2>
<p>We need to reach and sustain net zero CO₂ emissions to halt continued global warming. Models that emulate the transition to net zero CO₂ project large-scale cooling over land, and widespread reduction in land-based heat extremes.</p>
<p>However, post-net zero reductions in heat extremes favour regions with a higher human development index over regions with a lower index. This means the inequality of climate change may persist even after net zero CO₂. </p>
<p>Our study represents a step toward understanding climate extremes after net zero CO₂ emissions are achieved. For now, it is imperative that humanity works without delay to achieve net zero emissions to avoid the most severe climate change impacts affecting future generations.</p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/emissions-inequality-is-getting-worse-heres-how-to-end-the-reign-of-the-ultra-polluters-218308">Emissions inequality is getting worse – here's how to end the reign of the ultra-polluters</a>
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</em>
</p>
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<img src="https://counter.theconversation.com/content/214361/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrew King receives funding from the National Environmental Science Program. </span></em></p><p class="fine-print"><em><span>Josephine Brown receives funding from the National Environmental Science Program.</span></em></p><p class="fine-print"><em><span>Tilo Ziehn receives funding from the Australian Government under the National Environmental Science Program.</span></em></p><p class="fine-print"><em><span>Liam Cassidy does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>We can’t prevent continued global warming without reaching net zero carbon dioxide emissions. New climate simulations show what might happen when we get there.Liam Cassidy, PhD Candidate, The University of MelbourneAndrew King, Senior Lecturer in Climate Science, The University of MelbourneJosephine Brown, Senior Lecturer, The University of MelbourneTilo Ziehn, Principal Research Scientist, CSIROLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2167392023-11-23T01:19:08Z2023-11-23T01:19:08ZOur new high-resolution climate models are a breakthrough in understanding Australia’s future<p>Australia’s climate, already marked by <a href="https://www.science.org.au/supporting-science/science-policy-and-analysis/reports-and-publications/risks-australia-three-degrees-c-warmer-world">extremes with bushfires, heatwaves, storms and coastal flooding</a>, is only set to worsen with the <a href="https://nhess.copernicus.org/articles/21/941/2021/">growing effects of climate change</a>. </p>
<p>Disasters like the <a href="https://theconversation.com/australias-black-summer-of-fire-was-not-normal-and-we-can-prove-it-172506">Black Summer bushfires</a> of 2019–20 and the 2022 eastern Australian floods are likely to become <a href="https://www.nature.com/articles/s41467-021-27225-4">more frequent and intense</a>. </p>
<p>If carbon emissions continue at the current rate, climate change may make Australia <a href="https://theconversation.com/seriously-ugly-heres-how-australia-will-look-if-the-world-heats-by-3-c-this-century-157875">unbearable for future generations</a>. It’s a confronting outlook, and we need better tools to understand future impacts so we can adapt to them. </p>
<p>In our new research, <a href="https://doi.org/10.1029/2023EF003548">published in the journal Earth’s Future</a>, we have “downscaled” the latest global climate models to a 10-kilometre resolution across Australia. Having such a high resolution significantly enhances current global projections, with great improvements in projecting temperature, precipitation and extreme weather patterns for Australia. </p>
<p>Our new dataset is very useful. It provides scientists, policymakers and stakeholders with a valuable tool for comprehensively evaluating the potential impacts of climate change across Australia.</p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/every-australian-will-be-touched-by-climate-change-so-lets-start-a-national-conversation-about-how-well-cope-196934">Every Australian will be touched by climate change. So let's start a national conversation about how we'll cope</a>
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</em>
</p>
<hr>
<h2>Why do we need high-resolution climate projections?</h2>
<p>Climate models are key tools for understanding future climate risks. Current global climate models have a coarse resolution of 50–200km. This makes them <a href="https://doi.org/10.1029/2018EA000426">less suitable for local adaptation</a>. Regional climate models add <a href="https://wires.onlinelibrary.wiley.com/doi/full/10.1002/wcc.8">locally relevant details</a>, such as mountainous, coastal and urban regions.</p>
<p>For example, a high-resolution photo of a city lets you zoom in on the small details, such as people and vehicles. Likewise, high-resolution climate projections enable climate scientists to better simulate specific details such as storms and urban heat. They also help to track weather events like tropical cyclones – a meaningful refinement to understand local impacts of climate change.</p>
<p>This is why the Australian Royal Commission has recommended that future natural disaster risks are informed by <a href="https://www.royalcommission.gov.au/natural-disasters">high-resolution climate projections</a>. </p>
<p>High-resolution models also match up much better with real-world local geographical features such as mountains. This is important, as mountains play a role in both temperature and rainfall. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/558275/original/file-20231108-17-y2ej8c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A chart showing a detailed map versus a blurry one" src="https://images.theconversation.com/files/558275/original/file-20231108-17-y2ej8c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/558275/original/file-20231108-17-y2ej8c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=777&fit=crop&dpr=1 600w, https://images.theconversation.com/files/558275/original/file-20231108-17-y2ej8c.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=777&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/558275/original/file-20231108-17-y2ej8c.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=777&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/558275/original/file-20231108-17-y2ej8c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=976&fit=crop&dpr=1 754w, https://images.theconversation.com/files/558275/original/file-20231108-17-y2ej8c.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=976&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/558275/original/file-20231108-17-y2ej8c.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=976&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Here, you can see how the level of real-world detail improves in our regional, high-resolution model compared to a global one. For every global model region (also known as ‘grid cell’), our regional models produce 150 different estimates.</span>
<span class="attribution"><span class="source">Ralph Trancoso</span></span>
</figcaption>
</figure>
<h2>What the new projections show for Australia</h2>
<p>To produce high-resolution projections for Australia, we tapped into the <a href="https://www.carbonbrief.org/cmip6-the-next-generation-of-climate-models-explained/">most up-to-date climate model dataset</a> that’s coordinated by climate scientists globally. This is known as the Coupled Model Intercomparison Project, or CMIP6 for short.</p>
<p>The full CMIP6 dataset comprises hundreds of model simulations. As climate modelling is computationally expensive, we can’t downscale them all. Instead, we evaluated them to find the models that best represent Australia’s climate but also retain nearly a full range of future climate impacts.</p>
<p>This resulted in a set of 15 downscaled models and <a href="https://www.carbonbrief.org/explainer-how-shared-socioeconomic-pathways-explore-future-climate-change/">three emissions scenarios</a> representing low, intermediate and high emissions trajectories in the future.</p>
<p>Ours is the largest downscaled set of projections produced for Australia to date. The range of emissions scenarios is important for studies evaluating the impacts of climate change.</p>
<p>We evaluated our high-resolution projections by comparing their historical component (that is, the period between 1980 and 2010) to records measured at weather stations around Australia over that time. We examined temperature and precipitation (rain and snow), including their distribution, annual cycles and extremes.</p>
<p>Overall, we found our downscaling produced major improvements in how accurate the projections were. This was especially true for minimum temperature, which is important for looking at the impacts of heatwaves – high night-time temperatures can lead to <a href="https://www.nma.gov.au/defining-moments/resources/heatwaves">heat stress</a> and <a href="https://pubmed.ncbi.nlm.nih.gov/33195962/">even deaths</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/560923/original/file-20231121-4588-qj18u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A high up view of an azure ocean coast right next to a highrise city with mountains in the background" src="https://images.theconversation.com/files/560923/original/file-20231121-4588-qj18u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/560923/original/file-20231121-4588-qj18u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/560923/original/file-20231121-4588-qj18u.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/560923/original/file-20231121-4588-qj18u.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/560923/original/file-20231121-4588-qj18u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/560923/original/file-20231121-4588-qj18u.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/560923/original/file-20231121-4588-qj18u.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Projections are particularly improved in coastal, urban and mountain regions – where the Australian population is concentrated.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/aerial-view-gold-coast-queensland-australia-142759546">zstock/Shutterstock</a></span>
</figcaption>
</figure>
<p>We also looked at whether our models accurately represented day-to-day observations – that is, how well they matched up with actual weather recordings. The biggest difference came when looking at extremes (either very high or very low values), with a 142% improvement in representing minimum temperatures and an 87% improvement in representing winter maximum temperature. </p>
<p>Our models also worked well for precipitation. Predicting the number of days with no rain, as well as heavy rain days, is usually tricky for most models. Downscaling improved representation of dry days by 46% and extreme rain by 45%. This means we’ll have more reliable models when examining impacts from events like floods and droughts.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/faster-disaster-climate-change-fuels-flash-droughts-intense-downpours-and-storms-213242">Faster disaster: climate change fuels 'flash droughts', intense downpours and storms</a>
</strong>
</em>
</p>
<hr>
<h2>How will this be useful?</h2>
<p>The new projections provide more accurate data across Australia, but particularly in the mountains and densely populated coastal areas. This is important for disaster planning, preparedness and response. For example, in South East Queensland the improvements reached an impressive 150%.</p>
<p>The new data is not only more accurate, but offers a significantly clearer picture of the climatic future for densely populated regions. We can now have future climate information for shires and towns – an important step towards adaptation.</p>
<p>Downscaled climate projections based on the previous global suite of models have been used in Australia to understand <a href="https://www.sciencedirect.com/science/article/pii/S0048969720340432">future heatwaves</a>, <a href="https://www.disaster.qld.gov.au/__data/assets/pdf_file/0035/339299/QFES-Severe-Wind-Hazard-Exec-Summary.pdf">severe wind</a>, <a href="https://doi.org/10.1002/joc.7302">drought</a> and <a href="https://www.sciencedirect.com/science/article/pii/S0309170820306941">flood risks</a>. </p>
<p>Our new high-resolution dataset, based on the latest global models, provides scientists and stakeholders with a solid ground to support adaptation policies, inform communities, and build resilience and preparedness for future climate hazards in Australia.</p><img src="https://counter.theconversation.com/content/216739/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ralph leads the Queensland Future Climate Science Program - a collaborative program between the University of Queensland and Queensland's Department of Environment and Science undertaking applied climate science to support climate adaptation and natural disaster preparedness. </span></em></p><p class="fine-print"><em><span>Jozef Syktus is the Director of the University of Queensland and Department of Environment and Science (DES) collaborative research program. He was a science leader of the projects contributing the CSIRO Mk3.6 climate model simulations to the CMIP5 archive and dynamical downscaling of CMIP5 for Queensland. He led the development of the UQ-DES CMIP6 downscale projections for Australia. Jozef received funding from ARC, Queensland Government and CSIRO</span></em></p><p class="fine-print"><em><span>Sarah Chapman is a member of the Climate Projections and Services Team at the Department of Environment and Science, Queensland Government. </span></em></p>Global climate models don’t let us zoom in on the fine details. A new set of high-resolution climate models for Australia is solving this problem.Ralph Trancoso, Adjunct Associate Professor in Climate Change, The University of QueenslandJozef Syktus, Professorial Research Fellow, School of the Environment, The University of QueenslandSarah Chapman, Visiting Research Fellow, University of LeedsLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2170662023-11-07T19:35:06Z2023-11-07T19:35:06ZLuminous ‘mother-of-pearl’ clouds explain why climate models miss so much Arctic and Antarctic warming<figure><img src="https://images.theconversation.com/files/557912/original/file-20231106-267335-z7pv6c.jpg?ixlib=rb-1.1.0&rect=68%2C8%2C5682%2C3819&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/polar-stratospheric-cloud-known-nacreous-clouds-2197976813">YanaBu, Shutterstock</a></span></figcaption></figure><p>Our planet has warmed by about <a href="https://www.ipcc.ch/report/ar6/wg1/">1.2°C since 1850</a>. But this warming is <a href="https://theconversation.com/climate-explained-why-is-the-arctic-warming-faster-than-other-parts-of-the-world-160614">not uniform</a>. Warming at the poles, especially the Arctic, has been <a href="https://www.nature.com/articles/s43247-022-00498-3">three to four times faster</a> than the rest of the globe. It’s a phenomenon known as “polar amplification”. </p>
<p>Climate models simulate this effect, but when tested against the past 40 years of warming, <a href="https://www.nature.com/articles/s43247-022-00498-3">these models fall short</a>. The situation is even worse when it comes to modelling past climates with very high levels of greenhouse gases. </p>
<p>This is a problem because these are the same models used to project into the future and forecast how the climate will change. They are likely to underestimate what will happen later this century, including risks such as ice sheet melting or permafrost thawing. </p>
<p>In our <a href="https://www.nature.com/articles/s41561-023-01298-w">new research published today in Nature Geoscience</a> we used a high-resolution model of the atmosphere that includes the stratosphere. We found a special type of cloud appears over polar regions when greenhouse gas concentrations are very high. The role of this type of cloud has been overlooked so far. This is one of the reasons why our models are too cold at the poles. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/GVCaxb_AT8w?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Polar Stratospheric Clouds over Norway (Night Lights Films - Adrien Mauduit)</span></figcaption>
</figure>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/climate-explained-why-is-the-arctic-warming-faster-than-other-parts-of-the-world-160614">Climate explained: why is the Arctic warming faster than other parts of the world?</a>
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</p>
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<h2>Back to the future</h2>
<p>Looking into past climates can give us glimpses of possible futures for a range of extreme conditions. For us, this means we can use Earth’s history to find out how well our climate models perform. We can test our models by simulating episodes in the past when Earth was much warmer. The advantage of this is that we have temperature reconstructions for these episodes to evaluate the models, as opposed to the future, for which measurements are not available.</p>
<p>If we go back 50 million years or so, our planet was very hot. Carbon dioxide (CO₂) concentrations ranged between <a href="https://pubmed.ncbi.nlm.nih.gov/27111509/">900 and 1,900 parts per million (ppm)</a>, compared with 415 ppm today. Methane (CH₄) concentrations were likely also much higher. </p>
<p>Canada’s arctic archipelago was covered in <a href="https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abstract/124/1-2/3/125757/Life-at-the-top-of-the-greenhouse-Eocene-world-A?redirectedFrom=fulltext">lush rainforests</a> inhabited by alligators, turtles, lizards and mammals. </p>
<p>For these plants and animals to survive, conditions must have been warm and ice-free year-round. Indeed, surface ocean temperatures <a href="https://cp.copernicus.org/articles/16/2381/2020/">exceeded 20°C</a> near the north pole (at about 87°N) and <a href="https://www.sciencedirect.com/science/article/abs/pii/S0012821X12003081">25°C in the Southern Ocean</a> (at about 67°S). </p>
<p>This period called the early Eocene is a perfect test bed for our models, because it was globally very warm, and the poles were even warmer, meaning it was a climate with extreme polar amplification. In addition, the Eocene is recent enough for temperature reconstructions to be available. </p>
<p>But as it turns out, the models fail again. They are much <a href="https://web.ics.purdue.edu/%7Ehuberm/Climate_Dynamics_Prediction_Laboratory/Publications/Entries/2012/11/3_Citatiion__In_Reconstructing_Earths_Deep-Time_ClimateThe_State_of_the_Art_in_2012,_Paleontological_Society_Short_Course,_November_3,_2012._The_Paleontological_Society_Papers,_Volume_18,_Linda_C._Ivany_and_Brian_T._Huber_(eds.),_pp._213262_files/HuberPSPfinalpdfcolor.pdf">too cold at high latitudes</a>. What are our models missing?</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/557910/original/file-20231106-17-nm5nsb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An alligator partly submerged in a lake waiting, for it’s next meal. Clouds are reflected in the still water's surface." src="https://images.theconversation.com/files/557910/original/file-20231106-17-nm5nsb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/557910/original/file-20231106-17-nm5nsb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=341&fit=crop&dpr=1 600w, https://images.theconversation.com/files/557910/original/file-20231106-17-nm5nsb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=341&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/557910/original/file-20231106-17-nm5nsb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=341&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/557910/original/file-20231106-17-nm5nsb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=428&fit=crop&dpr=1 754w, https://images.theconversation.com/files/557910/original/file-20231106-17-nm5nsb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=428&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/557910/original/file-20231106-17-nm5nsb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=428&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Alligators, turtles, lizards and mammals lived in the Arctic about 50 million years ago, when it was much warmer than today.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/florida-alligator-sitting-lake-waiting-next-2294700385">Bradley GT, Shutterstock</a></span>
</figcaption>
</figure>
<h2>Polar stratospheric clouds</h2>
<p>In 1992 American paleoclimatologist Lisa Sloan suggested <a href="https://www.nature.com/articles/357320a0">polar stratospheric clouds</a> might have caused extreme warming at high latitudes in the past. </p>
<p>These clouds are a rare and beautiful sight today. They are also called <a href="https://glossary.ametsoc.org/wiki/Polar_stratospheric_clouds">nacreous or mother-of-pearl clouds</a> for their vivid and sometimes luminous colours. </p>
<p>They form at very high altitudes (in the stratosphere) and at very low temperatures (over the poles). In the present day climate, they appear mainly over Antarctica, but have also been observed during winter months over Scotland, Scandinavia and Alaska, at times when the stratosphere was particularly cold. </p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/explainer-what-are-the-nacreous-clouds-lighting-up-the-winter-skies-54095">Explainer: what are the 'nacreous clouds' lighting up the winter skies?</a>
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<p>Just like greenhouse gases, they absorb infrared radiation emitted by the Earth’s surface and re-emit a portion of this energy back to the surface. This suggests polar stratospheric clouds could be one of the missing puzzle pieces. </p>
<p>They warm the surface. And their effect could be significant, especially in winter, when the sun does not rise. But they are difficult to simulate in a climate model, so most models ignore them. This omission could explain why climate models miss some of the polar warming, because they miss a process that warms the poles.</p>
<p>Three decades after Sloan’s paper, a few atmosphere models are finally complex enough to allow us to test her hypothesis. In our <a href="https://www.nature.com/articles/s41561-023-01298-w">research</a> we use one of them and find that under certain conditions, the additional warming due to these polar stratospheric clouds exceeds 7°C during the winter months. This significantly reduces the gap between climate models and temperature evidence from the early Eocene. Sloan was right. </p>
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<h2>Implications for future projections</h2>
<p>Our research explains why climate models don’t work so well for past climates when greenhouse gas levels were much higher than they are today. But what about the future? Should we be concerned?</p>
<p>There is some good news. While polar stratospheric clouds do warm the poles, they won’t be as common in the future as they were in the distant past, even if both CO₂ and CH₄ reach very high levels.</p>
<p>This is due to another difference between the Eocene and today: the position of continents and mountains, which were different back then and which also influence the formation of polar stratospheric clouds. So even if we hit early Eocene levels of CH₄ and CO₂ in the future, we would expect less polar stratospheric cloud to be formed. This suggests the standard climate models are better at predicting the future than the past. </p>
<p>It’s therefore unlikely the Arctic and Antarctica will be covered by these beautiful clouds anytime soon. But our research shows evidence from past climates can reveal processes that only become important when greenhouse gas concentrations are high. Some of these processes are not included in our models because models are tested against present day observations and other processes simply seemed more important to include. Looking into the past is a way of broadening our horizon and learning for the future.</p>
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Read more:
<a href="https://theconversation.com/when-greenland-was-green-rapid-global-warming-55-million-years-ago-shows-us-what-the-future-may-hold-166342">When Greenland was green: rapid global warming 55 million years ago shows us what the future may hold</a>
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<img src="https://counter.theconversation.com/content/217066/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Katrin Meissner receives funding from the Australian Research Council. </span></em></p><p class="fine-print"><em><span>Deepashree Dutta received funding from the Australian Research Council and the Australian Government Research Training Program Scholarship. </span></em></p><p class="fine-print"><em><span>Martin Jucker receives funding from the Australian Research Council. </span></em></p>Back when there were Arctic alligators and turtles, ‘polar stratospheric clouds’ kept their world warm. Research suggests these clouds contribute to the ‘missing warming’ in climate models.Katrin Meissner, Professor and Director of the Climate Change Research Centre, UNSW, UNSW SydneyDeepashree Dutta, Postdoctoral Research Associate, University of CambridgeMartin Jucker, Lecturer in Atmospheric Dynamics, UNSW SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2105672023-08-01T15:42:09Z2023-08-01T15:42:09ZNuclear war would be more devastating for Earth’s climate than cold war predictions – even with fewer weapons<figure><img src="https://images.theconversation.com/files/540436/original/file-20230801-25-j40doe.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C5615%2C3000&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/missiles-aimed-sky-sunset-nuclear-bomb-2145373151">Hamara/Shutterstock</a></span></figcaption></figure><p>Christopher Nolan’s biopic of <a href="https://theconversation.com/now-i-am-become-death-the-destroyer-of-worlds-who-was-atom-bomb-pioneer-robert-oppenheimer-209398">J. Robert Oppenheimer</a> has revived morbid curiosity in the destructive power of nuclear weapons. There are now an estimated <a href="https://www.theguardian.com/world/2023/jun/12/number-of-nuclear-weapons-held-by-major-powers-rising-says-thinktank">12,512 nuclear warheads</a>. </p>
<p>A war in which even a fraction of these bombs were detonated would create blast waves and fires capable of killing millions of people almost instantly. The <a href="https://www.atomicarchive.com/resources/documents/effects/wenw/chapter-2.html">radiation-induced cancers and genetic damage</a> would affect the remaining population for generations.</p>
<p>But what sort of world would remain amid the radioactive fallout? For the last four decades, scientists modelling the Earth system have run computer simulations to find out. </p>
<p>Using their knowledge of chemistry and climate modelling, atmospheric scientists <a href="https://www.nobelprize.org/prizes/chemistry/1995/crutzen/facts/">Paul Crutzen</a> and <a href="https://twobtech.com/john-birks.html">John Birks</a> wrote a <a href="https://www.jstor.org/stable/4312777">short paper</a> in 1982 which suggested a nuclear war would produce a smoke cloud so massive that it would cause what became known as a nuclear winter. This, they claimed, would devastate agriculture and with it, civilisation.</p>
<p>A year later, scientists from the <a href="https://acp.copernicus.org/articles/23/6691/2023/">US and Soviet Union confirmed</a> first that cities and industrial complexes hit by nuclear weapons would indeed produce much more smoke and dust than burning the equivalent area of forest. And second, this global layer of smog would block out sunlight, causing conditions at Earth’s surface to become rapidly colder, dryer and darker. </p>
<p>Climate modelling shows the reduced sunlight would plunge global temperatures by up to <a href="https://acp.copernicus.org/articles/23/6691/2023/">10˚C for nearly a decade</a>. These freezing conditions, combined with less sunlight for plants to photosynthesise, would have catastrophic consequences for global food production and lead to mass starvation worldwide.</p>
<p><a href="https://theconversation.com/three-reasons-why-climate-change-models-are-our-best-hope-for-understanding-the-future-175936">Modern climate models</a> are much more sophisticated than those used in the 1980s. And while there are fewer nukes in working order today, more recent results from computer simulations suggest that the grim prophecy delivered by scientists 40 years ago may actually have been an underestimate.</p>
<figure class="align-center ">
<img alt="A black-and-white photograph of a mushroom cloud." src="https://images.theconversation.com/files/540437/original/file-20230801-19-mlvhwo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/540437/original/file-20230801-19-mlvhwo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=473&fit=crop&dpr=1 600w, https://images.theconversation.com/files/540437/original/file-20230801-19-mlvhwo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=473&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/540437/original/file-20230801-19-mlvhwo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=473&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/540437/original/file-20230801-19-mlvhwo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=595&fit=crop&dpr=1 754w, https://images.theconversation.com/files/540437/original/file-20230801-19-mlvhwo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=595&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/540437/original/file-20230801-19-mlvhwo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=595&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">The first detonation of a nuclear bomb: the Trinity test in New Mexico, US on July 16 1945.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/first-atomic-explosion-on-july-16-249574276">Everett Collection/Shutterstock</a></span>
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<h2>Clear and present danger</h2>
<p>Environmental scientists led by Alan Robock at Rutgers University in the US argued in <a href="https://acp.copernicus.org/articles/23/6691/2023/">a recent paper</a> that the nuclear winter theory helped end the proliferation of nuclear weapons during the cold war. In 1986, <a href="https://www.nytimes.com/1985/02/12/world/transcript-of-interview-with-president-on-a-range-of-issues.html?pagewanted=all">President Ronald Reagan</a> and <a href="https://www.salon.com/2000/09/07/gorbachev/">General Secretary Mikhail Gorbachev</a> took the first steps in history to reduce the number of nuclear weapons while citing the predicted consequences of a nuclear winter for all life on Earth. </p>
<p>At the height of the arms race in the mid-1980s there were over 65,000 nuclear weapons. The reduction in the global nuclear arsenal to <a href="https://thebulletin.org/nuclear-notebook/">just over 12,000</a> (of which 4,000 are on operational standby) has ebbed the threat of all-out nuclear war, prompting some to question whether the <a href="https://thebulletin.org/2022/02/us-defense-to-its-workforce-nuclear-war-can-be-won/">limited climate models</a> used in the 1980s had understated the consequences of a global nuclear war. </p>
<p>Newer and more <a href="https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2006JD008235">sophisticated climate models</a>, the ones used to <a href="https://theconversation.com/three-reasons-why-climate-change-models-are-our-best-hope-for-understanding-the-future-175936">model future climate changes</a> caused by the burning of fossil fuels, suggest the opposite is true.</p>
<p>With the largest possible nuclear exchange between the US and Russia, new models suggest the <a href="https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2021AV000610">ocean would cool</a> so profoundly that the world would be thrust into a “nuclear little ice age” lasting thousands of years.</p>
<p>Of course, there are seven <a href="https://www.icanw.org/nuclear_arsenals">other nuclear states</a>: China, France, India, Israel, North Korea, Pakistan and the UK. Scientists have modelled that even a limited nuclear war <a href="https://www.bbc.co.uk/news/world-asia-india-64396138">between India and Pakistan</a> could kill 130 million people and deprive <a href="https://www.nature.com/articles/s43016-022-00573-0">a further 2.5 billion</a> of food for at least two years.</p>
<p>A nuclear war is unlikely to remain limited, however. What starts with one tactical nuclear strike or a tit-for-tat exchange between two countries could <a href="https://sgs.princeton.edu/the-lab/plan-a">escalate</a> to an all-out nuclear war ending in utter destruction. A global nuclear war including the US, Europe and China could result in 360 million people dead and condemn nearly 5.3 billion people to starvation in the two years <a href="https://www.nature.com/articles/s43016-022-00573-0">following the exchange</a>.</p>
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<h2>The threat remains</h2>
<p>Scientific modelling allows us to peer into the abyss of a nuclear war without having to experience it. Forty years of scientific research into these <a href="https://thebulletin.org/2022/10/nowhere-to-hide-how-a-nuclear-war-would-kill-you-and-almost-everyone-else/">possibilities</a> encouraged the adoption of a United Nations treaty on the prohibition of nuclear weapons in 2017 – ratified by most countries but not the nine nuclear powers. </p>
<p>The <a href="https://www.icanw.org/nobel_prize">international campaign to abolish nuclear weapons</a> was awarded a Nobel Peace Prize that same year for its work in highlighting the catastrophe that would result from any use of nuclear weapons.</p>
<p>But the war in Ukraine has brought old fears to the surface. President Vladimir Putin of Russia has threatened a <a href="https://www.reuters.com/world/putin-update-russias-elite-ukraine-war-major-speech-2023-02-21/">limited use of nuclear weapons</a> as part of the conflict, and a single launch could escalate into a regional or even global exchange that would plunge billions of people into a world so harrowing we can barely comprehend it.</p>
<p>Robock said that it is now “even more urgent” for scientists to study the consequences of detonating nuclear weapons and ensure as many people as possible know about them. And, ultimately, to work for the elimination of these weapons. The threat of nuclear war has not gone away, and a nuclear ice age which would doom much of life on Earth for millennia is still a possibility.</p>
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<img alt="Imagine weekly climate newsletter" src="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p><strong><em>Don’t have time to read about climate change as much as you’d like?</em></strong>
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<hr><img src="https://counter.theconversation.com/content/210567/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mark Maslin is the UNFCCC designated point of contact for UCL. He is co-director of the London NERC Doctoral Training Partnership and a member of the Climate Crisis Advisory Group. He is a member of the Sopra-Steria CSR Board, Sheep Included Ltd, Lansons and NetZeroNow advisory boards. He has received grant funding from the NERC, EPSRC, ESRC, DFG, Royal Society, DIFD, BEIS, DECC, FCO, Innovate UK, Carbon Trust, UK Space Agency, European Space Agency, Research England, Wellcome Trust, Leverhulme Trust, CIFF, Sprint2020, and British Council. He has received funding from the BBC, Lancet, Laithwaites, Seventh Generation, Channel 4, JLT Re, WWF, Hermes, CAFOD, HP and Royal Institute of Chartered Surveyors. </span></em></p>Climate modelling in the 1980s offered the first glimpses of what might lie beyond a nuclear war.Mark Maslin, Professor of Earth System Science, UCLLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2079252023-06-20T04:38:20Z2023-06-20T04:38:20ZIs climate change outpacing our ability to predict extreme heatwaves?<p>When an extreme weather event happens somewhere in the world these days, it’s common to read quotes from climate scientists explaining this is exactly the kind of event we expect to see more often as climate change progresses. Such events are often devastating, but not surprising if you’ve been paying attention to the climate projections issued by scientists for many decades now.</p>
<p>But every so often, an event is so extreme it causes scientists to question our understanding of just how fast climate change is progressing. One such event was the heatwave across the Pacific Northwest region of the United States and Canada in the northern summer of 2021, when temperatures at some locations <a href="https://www.climatehubs.usda.gov/hubs/northwest/topic/2021-northwest-heat-dome-causes-impacts-and-future-outlook">hit 49°C</a> (121°F) – hotter than the all-time record for Texas. </p>
<p>It broke heat records by such a wide margin that scientists were <a href="https://edition.cnn.com/2021/07/20/world/climate-change-extreme-weather-speed-cmd-intl/index.html">quoted</a> in the <a href="https://www.nationalobserver.com/2021/07/21/news/climate-change-scientists-heat-wave-summer">media</a> saying they hadn’t expected to see temperatures so high in the Pacific Northwest until much later this century.</p>
<p>The basic concern for these scientists was that our computer climate models are best at simulating things that span large areas and long time periods, such as the annual average global temperature (what we broadly mean when we say “the climate”). They aren’t as good at simulating smaller-scale things such as an individual storm or hot wind (that is, “the weather”).</p>
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<strong>
Read more:
<a href="https://theconversation.com/statistically-impossible-heat-extremes-are-here-we-identified-the-regions-most-at-risk-204480">'Statistically impossible' heat extremes are here – we identified the regions most at risk</a>
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<p>It’s not that our models can’t simulate small-scale weather – they’re basically the same models we use for weather forecasting – it’s just very computationally expensive to have them zoom in and run in “weather mode” to get a highly detailed simulation. It’s feasible for a seven-day weather forecast, but not for a century-long climate simulation. </p>
<p>Given this limitation, the scientists quoted in the media were concerned extreme weather events might be more sensitive to climate change than our models suggest.</p>
<h2>Quantity matters too</h2>
<p>While these concerns around the <em>quality</em> of our model simulations at weather-relevant scales are valid, what’s often overlooked is the <em>quantity</em> of model simulations involved. Given the natural variability in the climate system, scientists prefer not to rely on just one model simulation when making climate projections. Instead, they run a range of century-long simulations – from just a handful up to 50 or more for the most well-resourced modelling groups – and look at the range of possible outcomes.</p>
<p>For climate metrics such as the annual average global temperature, that’s enough simulations to capture the full range of possibilities. It’s a value that doesn’t vary much from year to year because it’s an average over the entire globe, so the climate change signal dominates over natural variability. To use a slightly more technical term, we say it has a high “signal-to-noise” ratio.</p>
<p>In contrast, the weather can vary greatly over relatively short time frames, and therefore has a very low climate signal-to-noise ratio. Something like the hottest day of the year at a given location is especially noisy, because small variations in the alignment of weather patterns can make all the difference between a regular hot day and a record-shattering one. </p>
<p>In this situation, many more simulations would be required to reliably estimate the upper limit on what extreme temperatures are possible.</p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/weather-and-climate-are-used-interchangeably-they-shouldnt-be-110129">"Weather" and "climate" are used interchangeably. They shouldn't be</a>
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<h2>How many simulations are enough?</h2>
<p>To try and understand how many model simulations would be needed, our <a href="https://doi.org/10.1088/2752-5295/acd714">recently published research</a> used a climate model to simulate 45,000 years’ worth of daily weather at Seattle-Tacoma airport in the Pacific Northwest. </p>
<p>We then went through a process of picking out 1,000 random samples of 100 years of data from this population of 45,000 years, then 1,000 samples of 500 years, 1,000 years, 5,000 years, and so on. For each sample, we wrote down the maximum daily temperature we found (that is, the record temperature produced in each of these sample simulations). </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/532493/original/file-20230618-29-iflkh5.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/532493/original/file-20230618-29-iflkh5.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=483&fit=crop&dpr=1 600w, https://images.theconversation.com/files/532493/original/file-20230618-29-iflkh5.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=483&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/532493/original/file-20230618-29-iflkh5.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=483&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/532493/original/file-20230618-29-iflkh5.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=607&fit=crop&dpr=1 754w, https://images.theconversation.com/files/532493/original/file-20230618-29-iflkh5.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=607&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/532493/original/file-20230618-29-iflkh5.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=607&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Distribution of record temperatures at Seattle Tacoma airport for 1000 repeated sub-samples of varying size.</span>
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<p>To our surprise, as the samples got bigger, the record temperatures we found showed little evidence of stabilising. They just continued to grow, indicating even samples spanning several thousand years are insufficient to capture the full range of possible extreme temperatures. </p>
<p>The reason we kept finding hotter days as the sample size grew is that the larger samples included more weather patterns. This meant there was a greater chance of producing a unique pattern with the near-perfect alignment of weather systems to generate even more heat at our fixed location. It turns out the weather patterns that produce the most extreme heat are very unique – and indeed far rarer than we’d expected.</p>
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<img alt="" src="https://images.theconversation.com/files/532494/original/file-20230618-17-72qkt0.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/532494/original/file-20230618-17-72qkt0.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=186&fit=crop&dpr=1 600w, https://images.theconversation.com/files/532494/original/file-20230618-17-72qkt0.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=186&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/532494/original/file-20230618-17-72qkt0.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=186&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/532494/original/file-20230618-17-72qkt0.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=234&fit=crop&dpr=1 754w, https://images.theconversation.com/files/532494/original/file-20230618-17-72qkt0.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=234&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/532494/original/file-20230618-17-72qkt0.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=234&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">The weather pattern for the hottest day at Seattle Tacoma airport (green cross) in the observational record (June 28 2021, left) and our model simulations (right). The similarity between the two suggests extremely hot days in the model are generated by similar weather patterns as in the real world.</span>
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<h2>Luck of the draw</h2>
<p>From this perspective, the record-shattering heat experienced in the Pacific Northwest in 2021 was due not just to the overall trend of global heating, but also to the random shuffling of the weather. And our research suggests the latter factor plays an even larger role in this type of event than many climatologists had suspected. </p>
<p>This means that even though the Pacific Northwest heatwave broke records by such a wide margin, that is not necessarily a sign climate change is happening faster than expected, or that our models are doing a bad job of simulating how climate change increases the likelihood of extreme heatwaves.</p>
<p>It could simply be that our sample sizes are too small. If we had run more model simulations we could have simulated the right chance alignment of weather to generate a record-shattering day, meaning this real-life heatwave wouldn’t then have outstripped climatologists’ predictions to such an extent.</p>
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Read more:
<a href="https://theconversation.com/the-north-american-heatwave-shows-we-need-to-know-how-climate-change-will-change-our-weather-163802">The North American heatwave shows we need to know how climate change will change our weather</a>
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<p>Advances in supercomputers have traditionally been used to run climate models at higher resolution (that is, to zoom in and get closer to “weather mode”). But when it comes to predicting just how extreme the weather can get in a warming world, we might get more bang for our buck by using those advances to run many more simulations as well. That will show us what kind of extreme heat is possible as a rare event now, and what will be more commonplace in the coming decades.</p><img src="https://counter.theconversation.com/content/207925/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The 2021 Pacific Northwest heatwave outstripped even the most severe climate prections. A new study simulated 45,000 years of weather at Seattle Tacoma airport to try and figure out why.Damien Irving, Climate Data Scientist, CSIROJames Risbey, Researcher, Oceans and Atmosphere, CSIROLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2075742023-06-14T15:44:53Z2023-06-14T15:44:53ZAviation turbulence soared by up to 55% as the world warmed – new research<figure><img src="https://images.theconversation.com/files/531659/original/file-20230613-27-xtjkgf.jpg?ixlib=rb-1.1.0&rect=1609%2C334%2C1987%2C1917&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Potentially dangerous air turbulence has increased on busy flight routes across the globe.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/cumulonimbus-airplane-landing-storm-clouds-77635738">Jaromir Chalabala/Shutterstock</a></span></figcaption></figure><p>Turbulence on flights isn’t most people’s idea of fun. Drinks start wobbling, hearts start racing and even rational minds start to wonder whether the aircraft can cope. But for the <a href="https://doi.org/10.3389/fpsyg.2016.00754">many people</a> who have a diagnosable fear of flying, turbulence can be terrifying.</p>
<p>That’s why it has given us no great pleasure to have published many studies over the past decade predicting that climate change will worsen turbulence in the future. But these studies have left one gaping question unanswered: given that humans started changing the climate over a century ago, has atmospheric turbulence already started to increase?</p>
<p>According to <a href="https://doi.org/10.1029/2023GL103814">our new study</a>, the answer is a resounding yes. Over the course of the past four decades, severe turbulence has increased on many busy flight routes around the world, including in Europe, the US and the north Atlantic.</p>
<figure class="align-center ">
<img alt="A man sat in front of an airplane window with his head in his hands." src="https://images.theconversation.com/files/531664/original/file-20230613-29-5kqhvn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/531664/original/file-20230613-29-5kqhvn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/531664/original/file-20230613-29-5kqhvn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/531664/original/file-20230613-29-5kqhvn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/531664/original/file-20230613-29-5kqhvn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/531664/original/file-20230613-29-5kqhvn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/531664/original/file-20230613-29-5kqhvn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Many people have a diagnosable fear of flying.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/man-sits-front-airplane-window-nervous-2027486114">Marko Aliaksandr/Shutterstock</a></span>
</figcaption>
</figure>
<h2>The climate–turbulence link</h2>
<p>Clear-air turbulence is an invisible form of rough air that is undetectable by in-flight weather radar and is challenging to forecast. It has nothing to do with clouds and storms, but instead is generated by windshear (wind variations with altitude), which is concentrated largely in the jet streams.</p>
<p>Windshear in the jet streams has <a href="http://dx.doi.org/10.1038/s41586-019-1465-z">increased by 15%</a> at aircraft cruising altitudes since satellites began observing it in 1979. A further increase of <a href="https://doi.org/10.1029/2020EA001556">around 17%–29%</a> is projected by 2100. </p>
<p>These increases are consistent with the expected effects of climate change: <a href="https://feedbackloopsclimate.com/atmosphere">atmospheric feedback loops</a> (where warming generates further warming) are strengthening the temperature differences that generate windshear in the upper atmosphere.</p>
<p>That’s why climate models indicate that clear-air turbulence will <a href="http://dx.doi.org/10.1038/nclimate1866">become much more common in future</a>. Turbulence strong enough to pose an injury risk could <a href="http://dx.doi.org/10.1007/s00376-017-6268-2">double or triple</a> in frequency. </p>
<p>These increases are projected to occur all around the world. Some regions, including North America, the north Atlantic and Europe, are set to experience <a href="http://dx.doi.org/10.1002/2017GL074618">several hundred per cent</a> more turbulence in the coming decades. Every additional 1°C of global warming <a href="https://doi.org/10.1007/s00382-023-06694-x">will increase</a> the amount of turbulence further still.</p>
<p>And for those wondering whether climate models can be trusted with the task of making future turbulence predictions, <a href="http://dx.doi.org/10.1002/qj.4270">the evidence shows that they can</a>. The key factor limiting these predictions is not the performance of the climate models, but our understanding of turbulence itself.</p>
<figure class="align-center ">
<img alt="Weather radar screen inside the cockpit of an aircraft." src="https://images.theconversation.com/files/531933/original/file-20230614-31-aaakle.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/531933/original/file-20230614-31-aaakle.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=225&fit=crop&dpr=1 600w, https://images.theconversation.com/files/531933/original/file-20230614-31-aaakle.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=225&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/531933/original/file-20230614-31-aaakle.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=225&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/531933/original/file-20230614-31-aaakle.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=283&fit=crop&dpr=1 754w, https://images.theconversation.com/files/531933/original/file-20230614-31-aaakle.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=283&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/531933/original/file-20230614-31-aaakle.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=283&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Clear-air turbulence is undetectable by in-flight weather radar.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/cu-on-airplane-weather-radar-screen-2207518471">Supamotionstock.com/Shutterstock</a></span>
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</figure>
<h2>Past turbulence trends</h2>
<p>So have the predicted turbulence increases already begun? A previous analysis of pilot reports of turbulence found <a href="https://doi.org/10.1175/2008JAMC1799.1">evidence of an upward trend</a>. But the short coverage period of 12 years raised questions about whether the increase was genuine or simply a statistical blip. </p>
<p>A longer study analysed 44 years of atmospheric data from 1958 to 2001 and found <a href="https://doi.org/10.1029/2006JD008189">turbulence increases of 40%–90%</a>. But the lack of satellite data for the first half of this period leaves huge observational gaps and raises questions about the reliability of the results.</p>
<p>Our new study analyses turbulence in atmospheric data over the entire meteorological satellite era, from 1979 onwards. Although satellites cannot detect clear-air turbulence, what they can measure is the three-dimensional shape and structure of the jet streams. </p>
<p>From this we can calculate how much clear-air turbulence was being generated by the windshear. Our work has produced the most detailed picture yet of how turbulence has already started to change around the world.</p>
<p>We find that severe clear-air turbulence has increased by 55% over the north Atlantic and 41% over the US since 1979. It does go up and down from one year to the next, but there’s a clear long-term upward trend, consistent with the expected effects of climate change. We find similar increases on other busy flight routes over Europe, the Middle East and the south Atlantic.</p>
<h2>The future of turbulence</h2>
<p>We’ve been warning for the past decade that climate change would increase atmospheric turbulence. And now we see that it is happening. So what can be done to stop the more turbulent atmosphere leading to bumpier flights and more injuries to passengers and crew?</p>
<p>The aviation sector uses <a href="https://www.aviationweather.gov/turbulence/gtg">specialised turbulence forecasts</a> to plot smooth flight routes around turbulent air. These forecasts have improved greatly over the past few decades, but there is still plenty of room for improvement. </p>
<p>Technological advances might one day allow pilots to <a href="http://www.delicat.inoe.ro">remotely sense</a> invisible clear-air turbulence from the cockpit in real time. But high costs mean such technology is not yet viable.</p>
<figure class="align-center ">
<img alt="Fasten Seat belt sign on a plane." src="https://images.theconversation.com/files/531936/original/file-20230614-9255-jl252o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/531936/original/file-20230614-9255-jl252o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/531936/original/file-20230614-9255-jl252o.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/531936/original/file-20230614-9255-jl252o.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/531936/original/file-20230614-9255-jl252o.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/531936/original/file-20230614-9255-jl252o.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/531936/original/file-20230614-9255-jl252o.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The best advice to passengers is to keep your seatbelt fastened.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/security-on-plane-fasten-seat-belt-664653046">marako85/Shutterstock</a></span>
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</figure>
<p>For now, the best advice to passengers is to keep your seatbelt fastened. It’s what you do when driving down the road at 20mph, so it makes sense to do it when hurtling through the sky at 600mph. During a turbulence encounter, remember that turbulence strong enough to cause injuries is relatively rare.</p>
<p>If that thought doesn’t calm you down, we have heard that it helps to order a large drink, place it on the table in front of you and observe how little the liquid surface actually moves. You will see that the turbulent forces are rarely as bad as they feel.</p>
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<figure class="align-right ">
<img alt="Imagine weekly climate newsletter" src="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p><strong><em>Don’t have time to read about climate change as much as you’d like?</em></strong>
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<hr><img src="https://counter.theconversation.com/content/207574/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Paul D. Williams has received funding from the Royal Society, Natural Environment Research Council, Leverhulme Trust, European Union, and Heathrow Airport.</span></em></p><p class="fine-print"><em><span>Isabel Smith receives funding from NERC</span></em></p><p class="fine-print"><em><span>Mark Prosser receives funding from NERC. </span></em></p>Turbulence strong enough to pose an injury risk could be set to double or triple in frequency in the future.Paul Williams, Professor of Atmospheric Science, University of ReadingIsabel Smith, PhD Candidate, Meteorology, University of ReadingMark Prosser, PhD Student in the Department of Meteorology, University of ReadingLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2052922023-05-10T20:01:28Z2023-05-10T20:01:28ZSmoke from the Black Summer fires could have made the triple La Niña more likely<p>The 2019-2020 bushfire season was devastating. Vast areas of pristine forest burned, many for the first time in memory. By some estimates, a billion native animals died up and down Australia’s east coast. Dozens of people died. </p>
<p>While Sydney’s skies are blue again, Australia’s Black Summer has kept scientists around the globe busy. The sheer size of these megafires produced startling effects. Recently, researchers found the huge volumes of smoke <a href="https://www.abc.net.au/news/2023-03-10/how-the-black-summer-bushfires-depleted-the-ozone-layer/102076136">ate away</a> at our protective ozone layer. </p>
<p>Now, <a href="https://dx.doi.org/10.1126/sciadv.adg1213">new research</a> by American scientists suggests the Black Summer fires were massive enough to influence the <a href="https://cosmosmagazine.com/earth/enso-iod-weather-patterns-explainer/#:%7E:text=El%20Ni%C3%B1o%20and%20La%20Ni%C3%B1a%2C%20also%20called%20El%20Ni%C3%B1o%20Southern,to%20the%20north%20of%20Australia.">El Niño Southern Oscillation cycle</a>. It’s one of the most important drivers of unusual weather over the entire globe – and one which Australians know intimately.</p>
<p>The <a href="https://theconversation.com/la-nina-is-finishing-an-extremely-unusual-three-year-cycle-heres-how-it-affected-weather-around-the-world-196561">three successive years</a> of La Niña we just had? They could have been made more likely by the Black Summer fires. The reason, strangely enough, is the smoke. </p>
<p>But it’s important not to say the link is proven. While groundbreaking, this research relies on a single model. It’s too early to clearly say bushfire smoke can trigger La Niña. </p>
<h2>Where there’s fire, there’s smoke</h2>
<p>We’ve long known that the huge volume of ash blown high into the upper atmosphere by a big volcanic eruption can cool Earth’s surface for many months, or <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-i/">even years</a>. </p>
<p>We also know volcanoes <a href="https://doi.org/10.1007/s41748-022-00331-z">can influence</a> the tropical Pacific, and thus affect whether an El Niño or a La Niña phase develops. </p>
<p>How? By blocking light. Particles of ash reduce how much light gets to the surface. </p>
<p>Volcanic ash gets blown high into the stratosphere, the part of the atmosphere just above the clouds where long-haul airplanes fly. Then, sunlight gets reflected before it reaches the ground, thus cooling the surface much like an umbrella can. </p>
<h2>Is bushfire smoke the same as volcanic ash?</h2>
<p>It’s tempting to equate smoke with ash, and assume a large enough bushfire would have similar effects to a volcano. </p>
<p>But there are important differences. Most obviously, a bushfire does not smell of rotten eggs.</p>
<p>That might sound unimportant, but the rotten egg smell – which comes from sulfur – indicates major differences in the composition of volcanic ash and bushfire smoke. </p>
<p>Different chemicals could mean very different responses to sunlight once in the atmosphere, which in turn could affect how much light is reflected. </p>
<p>Second, bushfires don’t explode.</p>
<p>A decent volcano erupts with enough force to blast smoke high into the stratosphere. Bushfires don’t have the same propulsive force.</p>
<p>Bushfire smoke is hot, though, and hot smoke rises well. Some of the smoke from the Black Summer fires <a href="https://www.science.org/doi/abs/10.1126/science.abe1415">reached the stratosphere</a>, although after a much longer interval than for volcanic eruptions. </p>
<p>So, does a large bushfire have the same effect on climate as a volcano?</p>
<p>The American researchers begin by checking the similarities using climate model simulations. They found bushfire smoke does indeed shade the surface from sunlight in these simulations. </p>
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Read more:
<a href="https://theconversation.com/australias-black-summer-of-fire-was-not-normal-and-we-can-prove-it-172506">Australia's Black Summer of fire was not normal – and we can prove it</a>
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<p>How much? Over a region of the south-eastern Pacific, about 150 terawatts of sunlight bounced back to space – the equivalent of about 100,000 coal power plants. </p>
<h2>Clouds matter</h2>
<p>The surprising finding is how it happens. In contrast to eruptions, bushfire smoke didn’t reflect the sunlight directly. Instead, clouds were responsible. </p>
<p>How does that work? This is where the magic of the climate system kicks in. Our atmosphere, oceans and lands are constantly interacting with each other.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/525315/original/file-20230510-17-634wtl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Clouds over ocean" src="https://images.theconversation.com/files/525315/original/file-20230510-17-634wtl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/525315/original/file-20230510-17-634wtl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/525315/original/file-20230510-17-634wtl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/525315/original/file-20230510-17-634wtl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/525315/original/file-20230510-17-634wtl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=504&fit=crop&dpr=1 754w, https://images.theconversation.com/files/525315/original/file-20230510-17-634wtl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=504&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/525315/original/file-20230510-17-634wtl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=504&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Whiter, thicker clouds make the surface of the ocean cooler.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
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<p>In their simulations, Black Summer smoke was first blown eastward by strong winds in the atmosphere. Under specific conditions, some smoke particles can interact with droplets in clouds and make clouds thicker and brighter. One region where this can happen is the subtropical south-eastern Pacific. </p>
<p>The researchers were able to show the brightness of the clouds over this area increased considerably just around the time when the smoke particles arrived. </p>
<p>These brighter, whiter clouds reflected more sunlight back into space and shaded the surface underneath. The net effect: cooler seawater. </p>
<p>The effect was particularly important because of the timing. Smoke-whitened clouds emerged around our summer solstice in late December, which is the same time of year when the strength of the incoming sunlight peaks in the southern hemisphere.</p>
<p>How is this linked to La Niña? </p>
<p>Follow the chain: huge volumes of smoke blow east where they whiten clouds, cool the seawater, and cause less water to evaporate.</p>
<p>Surface winds carried this cooler, drier air over the tropical Pacific, where it cooled the ocean surface again, and made it harder for tropical storms to form.</p>
<p>A cooler sea surface in the tropical Pacific is a hallmark of La Niña, the cold phase of the El Niño Southern Oscillation cycle. </p>
<p>That’s how this research was able to trace a link between Black Summer smoke and the rare back-to-back La Niña events in 2019-20 and 2020-21. As you know, we ended up having an even rarer triple La Niña in 2021-22, though the research period ends before this. </p>
<h2>Is the link now proven? Not quite</h2>
<p>This study offers a consistent physical explanation for how bushfires might influence the El Niño cycle. </p>
<p>It’s yet another example of how complex climate science can be, and how much we can still be surprised and challenged by what mother nature presents us. </p>
<p>But there are a few caveats to keep in mind.</p>
<p>For one, the ENSO cycle in the simulation was heading for a double La Niña even without the impact of the smoke. The simulation stops in the winter of 2021, which is before the real-world ENSO tipped into a third La Niña. </p>
<p>What does that mean? In short, we can’t know for sure if the effect of the bushfire smoke really did cause the triple La Niña. </p>
<p>Another caveat is the fact the study relied on a single climate model, and relies heavily on the representation of clouds in that model.</p>
<p>That’s a potential problem, because we know clouds – and especially their interactions with aerosols like smoke – are still the largest source of uncertainties and model errors. </p>
<p>To prove or disprove the link, we’ll have to simulate the impact of ballooning Black Summer smoke plumes across many different models. </p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/smoke-from-the-black-summer-fires-created-an-algal-bloom-bigger-than-australia-in-the-southern-ocean-164564">Smoke from the Black Summer fires created an algal bloom bigger than Australia in the Southern Ocean</a>
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<img src="https://counter.theconversation.com/content/205292/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Martin Jucker does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Where there’s fire, there’s smoke – could plumes from the Black Summer of fire have cooled regions of the Pacific and triggered a La Niña? New research suggests it’s possible.Martin Jucker, Lecturer in Atmospheric Dynamics, UNSW SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2044122023-05-09T18:23:08Z2023-05-09T18:23:08ZClimate: modelling micro-algae to better understand the workings of the ocean<figure><img src="https://images.theconversation.com/files/525196/original/file-20230509-21-koy7o5.jpg?ixlib=rb-1.1.0&rect=0%2C17%2C1920%2C1258&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Diazotroph (_Trichodesmium_) bloom in the Coral Sea, captured on 1 September 2019 by the Landsat 8 satellite. The interaction between the physics and biology of the ocean is manifested in these green filaments that snake through the currents.</span> <span class="attribution"><a class="source" href="https://earthobservatory.nasa.gov/images/145610/a-bloom-of-nitrogen-fixing-bacteria">Joshua Stevens/NASA</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>The ocean absorbs <a href="https://www.nature.com/articles/s43017-022-00381-x">a quarter of the CO₂</a> given out by human activities, playing a major role in slowing climate change. To have a better grasp of these processes is crucial to understand the ocean’s role in the global climate system and to better foresee disruptions caused by the changing climate.</p>
<p><a href="https://theconversation.com/les-oceans-bientot-dotes-de-jumeaux-virtuels-pour-quoi-faire-160425">Numerical modeling</a> is among the most frequently used tools to do this. Through quantitive methods, it can simulate the interactions of important drivers of the climate, including atmosphere, oceans, land surface and ice. It represents the climate on a virtual planet earth, and is indispensable to explore past and predict future conditions, and to understand how our current climate works.</p>
<h2>The challenge of modelling the oceans</h2>
<p>These models rely on a series of equations governing the main physical, chemical and biological phenomena shaping the world’s climate. The difficulty of representing these forces comes from the complexity of simulating the physical and biological processes involved and how they interact with each other.</p>
<p>As far as the physics of the oceans is concerned, the equations are fairly well known and defined. Improving models depends above all on higher resolution, limited for the moment by the processing capacity and storage space of our computers.</p>
<p>When it comes to biological factors, however, there are lots of questions around how best to encode and simplify processes of the highest complexity. To boil it down: CO<sub>2</sub> capture is principally regulated by phytoplankton. These microscopic algae live on the surface areas of the ocean and absorb CO<sub>2</sub> via photosynthesis. When phytoplankton die, some of the organisms fall to the bottom of the ocean, providing a carbon store for hundreds, indeed thousands of years.</p>
<p>To represent phytoplankton, one of the commonest approaches is to divide it into “functional types” – that’s to say distinct groups of phytoplankton which have features in common such as size or feeding strategy. This approach assumes each type can have a different impact on the carbon cycle and play a different role in the ecosystem.</p>
<h2>Diazotrophs – allies of the climate</h2>
<p>One type in particular, diazotrophs, are under the spotlight at the moment. These organisms, as their name indicates, use nitrogen (N2) molecules for their growth (etymologically speaking, for feeding, from the Greek word <em>trophos</em>). By transforming N2, diazotrophs provide nutrients that are essential to other phytoplankton and allow them to photosynthesise. They thus have a fundamental role as natural fertilisers of the ocean.</p>
<p>Recent studies, in the field and the lab, have shown the great diversity of diazotrophs and their <a href="https://www.science.org/doi/10.1126/science.aay9514">adaptation to different environments</a>. For example, while it was previously thought diazotrophs were confined to warm, clear tropical waters, some unicellular diazotrophs have been discovered in <a href="https://www.pnas.org/doi/10.1073/pnas.1813658115">Arctic seas</a> or in the darkness of the <a href="https://ami-journals.onlinelibrary.wiley.com/doi/full/10.1111/1462%E2%80%932920.15645">deep ocean</a>.</p>
<p>For a long time, however, researchers have taken the view that diazotrophs contribute little to carbon sequestration, because <em>Trichodesmium</em> – historically the most studied diazotroph – tends to stay on the ocean surface and to be little subject to predation. But evidence has been gathered and shows other types of diazotroph (those in symbiosis with diatom algae) are involved in <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2012GL053356">significant carbon flows</a> toward the depths).</p>
<p>Despite their importance, diazotrophs are often represented in a very sketchy way in numerical models. This is a result of both our understanding of their physiology still being limited, and constraints in computing capacity – when one adds complexity to the models, simulations take more time or need more powerful processors.</p>
<p>Many Earth System models, like those used by the Intergovernmental Panel on Climate Change, still work on the basis of assuming that nitrogen is artificially added to the ocean’s surface in certain conditions supposedly favourable to diazotrophs.</p>
<p>Other models explicitly represent the nitrogen-fixing process, but restrict themselves to a single type of diazotroph with the characteristics of <em>Trichodesmium</em>. This is, however, a very reductive approach given scientific advances, and limits our capacity to capture the global distribution of microalgae, assess their impact on the rest of the ecosystem, and to predict the consequences of climate change both on phytoplankton and carbon sequestration.</p>
<h2>Better representation of diazotrophs in digital models</h2>
<p>To address these gaps, we have developed within the framework of project <a href="https://twitter.com/notion_project?lang=fr">NOTION</a> a brand new representation of diazotrophs, this time including three different types.</p>
<figure class="align-center ">
<img alt="Schematic drawing of the Pacific Ocean with bands of colour extending between Central America and Central Africa, with another shorter band at the latitude of Spain" src="https://images.theconversation.com/files/517767/original/file-20230327-1352-kegjgq.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/517767/original/file-20230327-1352-kegjgq.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=559&fit=crop&dpr=1 600w, https://images.theconversation.com/files/517767/original/file-20230327-1352-kegjgq.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=559&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/517767/original/file-20230327-1352-kegjgq.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=559&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/517767/original/file-20230327-1352-kegjgq.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=702&fit=crop&dpr=1 754w, https://images.theconversation.com/files/517767/original/file-20230327-1352-kegjgq.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=702&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/517767/original/file-20230327-1352-kegjgq.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=702&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Estimated nitrogen fixation rate for a day in November under average conditions. Each colour corresponds to a different type of diazotroph. Sometimes the bands overlap, indicating a mixture of diazotroph species.</span>
<span class="attribution"><span class="source">Domitille Louchard, Mar Benavides</span>, <span class="license">Fourni par l'auteur</span></span>
</figcaption>
</figure>
<p>If the equations describing diazotroph growth and mortality are the same, each type is distinguished from the others by specific factors, corresponding to how each type reacts to different temperatures, amount of sunlight or availability of nutrients.</p>
<p>This innovative representation of diazotrophs has been integrated into a high-resolution numerical model applied to the Atlantic Ocean – a diazotroph hotspot.</p>
<p>Accounting for the diversity of diazotrophs has resulted in an expansion of nitrogen fixing in digital models of the ocean, and closer accordance with field observations. Estimates of vertical carbon flows have also increased, notably in regions like the tropical West Atlantic, where diazotrophs in symbiosis with diatom algae flourish.</p>
<figure class="align-center ">
<img alt="Schematic drawing of the Pacific Ocean as in Figure 2. The presence of fixed nitrogen increases strongly from April, then falls back again from November" src="https://images.theconversation.com/files/517428/original/file-20230324-22-ibaffr.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/517428/original/file-20230324-22-ibaffr.gif?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=560&fit=crop&dpr=1 600w, https://images.theconversation.com/files/517428/original/file-20230324-22-ibaffr.gif?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=560&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/517428/original/file-20230324-22-ibaffr.gif?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=560&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/517428/original/file-20230324-22-ibaffr.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=703&fit=crop&dpr=1 754w, https://images.theconversation.com/files/517428/original/file-20230324-22-ibaffr.gif?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=703&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/517428/original/file-20230324-22-ibaffr.gif?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=703&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A year of surface nitrogen fixation using the new digital system developed within the Project NOTION framework. Simulation by Domitille Louchard at ETH Zurich.</span>
<span class="attribution"><span class="source">Domitille Louchard, Mar Benavides</span>, <span class="license">Fourni par l'auteur</span></span>
</figcaption>
</figure>
<p>The new model allows us to address understudied issues, such as competition between diazotrophs, but also to better understand the role microalgae play in the context of a changing planet. What is their importance as a source of nitrogen going to be for other producers at the bottom of the food chain? Can diazotrophs help limit the effects of climate change? The possibilities for further research opened up by this more realistic representation are huge.</p>
<hr>
<p><em>The NOTION research project described in this article is generously supported by <a href="https://group.bnpparibas/decouvrez-le-">Foundation BNP Paribas</a> as part of its <a href="https://group.bnpparibas/tempsforts/climate-biodiversity">Climate and Biodiversity Initiative</a>.</em></p>
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<p>Translation by <a href="https://twitter.com/JoshNeicho">Joshua Neicho</a></p><img src="https://counter.theconversation.com/content/204412/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Domitille Louchard has received funding from the BNP Paribas Foundation (Climate & Biodiversity initiative).</span></em></p><p class="fine-print"><em><span>Mar Benavides a reçu des financements de Climate & Biodiversity Initiative Fondation BNP Paribas, projet NOTION.</span></em></p>The ocean absorbs a quarter of the CO₂ emitted by humans, thanks in particular to phytoplankton, including diazotrophs. Knowing how to model them is crucial to understanding the ocean’s role in climate.Domitille Louchard, Assistant researcher, Swiss Federal Institute of Technology ZurichMar Benavides, Research scientist, Institut de recherche pour le développement (IRD)Licensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1923672022-10-20T08:06:51Z2022-10-20T08:06:51ZNoise in the brain enables us to make extraordinary leaps of imagination. It could transform the power of computers too<figure><img src="https://images.theconversation.com/files/490334/original/file-20221018-4769-ep7hqv.gif?ixlib=rb-1.1.0&rect=207%2C0%2C1587%2C992&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/video/clip-1039258709-ai-artificial-intelligence-digital-network-technologies-concepts">Shutterstock</a></span></figcaption></figure><p>We all have to make hard decisions from time to time. The hardest of my life was whether or not to change research fields after my PhD, from fundamental physics to climate physics. I had job offers that could have taken me in either direction – one to join Stephen Hawking’s <a href="http://www.damtp.cam.ac.uk/research/gr/about-us">Relativity and Gravitation Group</a> at Cambridge University, another to join the <a href="https://www.metoffice.gov.uk/">Met Office</a> as a scientific civil servant.</p>
<p>I wrote down the pros and cons of both options as one is supposed to do, but then couldn’t make up my mind at all. Like <a href="https://en.wikipedia.org/wiki/Buridan%27s_ass">Buridan’s donkey</a>, I was unable to move to either the bale of hay or the pail of water. It was a classic case of paralysis by analysis.</p>
<p>Since it was doing my head in, I decided to try to forget about the problem for a couple of weeks and get on with my life. In that intervening time, my unconscious brain decided for me. I simply walked into my office one day and the answer had somehow become obvious: I would make the change to studying the weather and climate.</p>
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<strong>
Read more:
<a href="https://theconversation.com/uncharted-brain-decoding-dementia-a-three-part-series-to-read-and-listen-to-193162">Uncharted Brain: Decoding Dementia – a three-part series to read and listen to</a>
</strong>
</em>
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<p>More than four decades on, I’d make the same decision again. My fulfilling career has included developing a <a href="https://www.ecmwf.int/en/about/media-centre/news/2022/symposium-prof-tim-palmer-take-place-5-and-6-december">new, probabilistic way of forecasting weather and climate</a> which is helping humanitarian and disaster relief agencies make better decisions ahead of extreme weather events. (This and many other aspects are described in my new book, <a href="https://global.oup.com/academic/product/the-primacy-of-doubt-9780192843593?lang=en&cc=gb">The Primacy of Doubt</a>.)</p>
<p>But I remain fascinated by what was going on in my head back then, which led my subconscious to make a life-changing decision that my conscious could not. Is there something to be understood here not only about how to make difficult decisions, but about how humans make the leaps of imagination that characterise us as such a creative species? I believe the answer to both questions lies in a better understanding of the extraordinary power of noise.</p>
<h2>Imprecise supercomputers</h2>
<p>I went from the pencil-and-paper mathematics of Einstein’s theory of general relativity to running complex climate models on some of the world’s biggest supercomputers. Yet big as they were, they were never big enough – the real climate system is, after all, very complex.</p>
<p>In the early days of my research, one only had to wait a couple of years and top-of-the-range supercomputers would get twice as powerful. This was the era where <a href="https://www.pcmag.com/encyclopedia/term/transistor#:%7E:text=In%20the%20digital%20world%2C%20a,or%20even%20billions%20of%20transistors.">transistors</a> were getting smaller and smaller, allowing more to be crammed on to each microchip. The consequent doubling of computer performance for the same power every couple of years was known as <a href="https://www.investopedia.com/terms/m/mooreslaw.asp">Moore’s Law</a>.</p>
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<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/288776/original/file-20190820-170910-8bv1s7.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/288776/original/file-20190820-170910-8bv1s7.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/288776/original/file-20190820-170910-8bv1s7.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/288776/original/file-20190820-170910-8bv1s7.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/288776/original/file-20190820-170910-8bv1s7.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/288776/original/file-20190820-170910-8bv1s7.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/288776/original/file-20190820-170910-8bv1s7.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p><strong><em>This story is part of Conversation Insights</em></strong>
<br><em>The Insights team generates <a href="https://theconversation.com/uk/topics/insights-series-71218">long-form journalism</a> and is working with academics from different backgrounds who have been engaged in projects to tackle societal and scientific challenges.</em></p>
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<p>There is, however, only so much miniaturisation you can do before the transistor starts becoming unreliable in its key role as an on-off switch. Today, with transistors starting to approach <a href="https://spectrum.ieee.org/smallest-transistor-one-carbon-atom">atomic size</a>, we have pretty much reached the limit of Moore’s Law. To achieve more number-crunching capability, computer manufacturers must bolt together more and more computing cabinets, each one crammed full of chips.</p>
<p>But there’s a problem. Increasing number-crunching capability this way requires a lot more electric power – modern supercomputers the size of tennis courts consume tens of megawatts. I find it something of an embarrassment that we need so much energy to try to accurately predict the effects of climate change.</p>
<p>That’s why I became interested in how to construct a more accurate climate model <em>without</em> consuming more energy. And at the heart of this is an idea that sounds counterintuitive: by adding random numbers, or “noise”, to a climate model, we can actually make it more accurate in predicting the weather.</p>
<h2>A constructive role for noise</h2>
<p>Noise is usually seen as a nuisance – something to be minimised wherever possible. In telecommunications, we speak about trying to maximise the “signal-to-noise ratio” by boosting the signal or reducing the background noise as much as possible. However, in <a href="https://en.wikipedia.org/wiki/Nonlinear_system">nonlinear systems</a>, noise can be your friend and actually contribute to boosting a signal. (A <a href="http://kolibri.teacherinabox.org.au/modules/en-boundless/www.boundless.com/algebra/textbooks/boundless-algebra-textbook/conic-sections-341/nonlinear-systems-of-equations-and-inequalities-52/models-involving-nonlinear-systems-of-equations-222-6108/index.html#:%7E:text=Some%20other%20real%2Dworld%20examples,is%20somewhere%20on%20a%20circle.">nonlinear system</a> is one whose output does not vary in direct proportion to the input. You will likely be very happy to win £100 million on the lottery, but probably not twice as happy to win £200 million.) </p>
<p>Noise can, for example, help us find the maximum value of a complicated curve such as in Figure 1, below. There are many situations in the physical, biological and social sciences as well as in engineering where we might need to find such a maximum. In my field of meteorology, the process of finding the best initial conditions for a global weather forecast involves identifying the maximum point of a very <a href="https://en.wikipedia.org/wiki/Numerical_weather_prediction">complicated meteorological function</a>.</p>
<p><strong>Figure 1</strong></p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/490372/original/file-20221018-8262-yoxe8v.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A curve with multiple local peaks and troughs" src="https://images.theconversation.com/files/490372/original/file-20221018-8262-yoxe8v.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/490372/original/file-20221018-8262-yoxe8v.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=292&fit=crop&dpr=1 600w, https://images.theconversation.com/files/490372/original/file-20221018-8262-yoxe8v.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=292&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/490372/original/file-20221018-8262-yoxe8v.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=292&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/490372/original/file-20221018-8262-yoxe8v.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=366&fit=crop&dpr=1 754w, https://images.theconversation.com/files/490372/original/file-20221018-8262-yoxe8v.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=366&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/490372/original/file-20221018-8262-yoxe8v.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=366&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A curve with multiple local peaks and troughs.</span>
<span class="attribution"><span class="license">Author provided</span></span>
</figcaption>
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<p>However, employing a “<a href="https://en.wikipedia.org/wiki/Deterministic_algorithm">deterministic algorithm</a>” to locate the global maximum doesn’t usually work. This type of algorithm will typically get stuck at a local peak (for example at point <strong>a</strong>) because the curve moves downwards in both directions from there.</p>
<p>An answer is to use a technique called “<a href="https://en.wikipedia.org/wiki/Simulated_annealing">simulated annealing</a>” – so called because of its similarities with (<a href="https://en.wikipedia.org/wiki/Annealing_(materials_science)">annealing</a>), the heat treatment process that changes the properties of metals. Simulated annealing, which employs noise to get round the issue of getting stuck at local peaks, has been used to solve many problems including the classic <a href="https://optimization.mccormick.northwestern.edu/index.php/Traveling_salesman_problems">travelling salesman puzzle</a> of finding the shortest path between a <a href="https://optimization.mccormick.northwestern.edu/index.php/File:48StatesTSP.png">large number of cities on a map</a>.</p>
<p>Figure 1 shows a possible route to locating the curve’s global maximum (point <strong>9</strong>) by using the following criteria:</p>
<ul>
<li><p>If a randomly chosen point is higher than the current position on the curve, then the new point is always moved to.</p></li>
<li><p>If it is lower than the current position, the suggested point isn’t necessarily rejected. It depends whether the new point is a lot lower or just a little lower.</p></li>
</ul>
<p>However, the decision to move to a new point also depends on how long the analysis has been running. Whereas in the early stages, random points quite a bit lower than the current position may be accepted, in later stages only those that are higher or just a tiny bit lower are accepted.</p>
<p>The technique is known as simulated annealing because early on – like hot metal in the early phase of cooling – the system is pliable and changeable. Later in the process – like cold metal in the late phase of cooling – it is almost rigid and unchangeable.</p>
<h2>How noise can help climate models</h2>
<p>Noise was introduced into <a href="https://www.metoffice.gov.uk/weather/climate/science/climate-modelling">comprehensive weather and climate models</a> around 20 years ago. A key reason was to represent model uncertainty in our ensemble weather forecasts – but it turned out that adding noise also reduced some of the biases the models had, making them more accurate simulators of weather and climate.</p>
<p>Unfortunately, these models require huge supercomputers and a lot of energy to run them. They divide the world into small gridboxes, with the atmosphere and ocean within each assumed to be constant – which, of course, it isn’t. The horizontal scale of a typical gridbox is around 100km – so one way of making a model more accurate is to reduce this distance to 50km, or 10km or 1km. However, halving the volume of a gridbox increases the computational cost of running the model by up to a factor of 16, meaning it consumes a lot more energy.</p>
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</figure>
<p>Here again, noise offered an appealing alternative. The <a href="https://www.nature.com/articles/s42254-019-0062-2">proposal</a> was to use it to represent the unpredictable (and unmodellable) variations in small-scale climatic processes like turbulence, cloud systems, ocean eddies and so on. I argued that adding noise could be a way of boosting accuracy without having to incur the enormous computational cost of reducing the size of the gridboxes. For example, <a href="https://journals.ametsoc.org/view/journals/clim/34/11/JCLI-D-20-0507.1.xml">as has now been verified</a>, adding noise to a climate model increases the likelihood of producing extreme hurricanes – reflecting the potential reality of a world whose weather is growing more extreme due to climate change.</p>
<p>The computer hardware we use for this modelling is inherently noisy – electrons travelling along wires in a computer move in partly random ways due to its warm environment. Such randomness is called “thermal noise”. Could we save even more energy by tapping into it, rather than having to use software to generate pseudo-random numbers? To me, low-energy <a href="https://www.nature.com/articles/526032a">“imprecise” supercomputers</a> that are inherently noisy looked like a win-win proposal. </p>
<p>But not all of my colleagues were convinced. They were uncomfortable that computers might not give the same answers from one day to the next. To try to persuade them, I began to think about other real-world systems that, because of limited energy availability, also use noise that is generated within their hardware. And I stumbled on the human brain.</p>
<h2>Noise in the brain</h2>
<p>Every second of the waking day, our eyes alone send gigabytes of data to the brain. That’s not much different to the amount of data a climate model produces each time it outputs data to memory.</p>
<p>The brain has to process this data and somehow make sense of it. If it did this using the power of a supercomputer, that would be impressive enough. But it does it using one millionth of that power, about 20W instead of 20MW – what it takes to power a lightbulb. Such energy efficiency is mind-bogglingly impressive. How on Earth does the brain do it?</p>
<p>An adult brain contains some 80 billion neurons. Each neuron has a long slender biological cable – the axon – along which electrical impulses are transmitted from one set of neurons to the next. But these impulses, which collectively describe information in the brain, have to be boosted by protein “transistors” positioned at regular intervals along the axons. Without them, the signal would dissipate and be lost.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/489566/original/file-20221013-18-isqtqg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Neurons and axons in the brain." src="https://images.theconversation.com/files/489566/original/file-20221013-18-isqtqg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/489566/original/file-20221013-18-isqtqg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/489566/original/file-20221013-18-isqtqg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/489566/original/file-20221013-18-isqtqg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/489566/original/file-20221013-18-isqtqg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=425&fit=crop&dpr=1 754w, https://images.theconversation.com/files/489566/original/file-20221013-18-isqtqg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=425&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/489566/original/file-20221013-18-isqtqg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=425&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Brain neurons and axons under a microscope.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/neurons-brain-on-white-background-307043336">Shutterstock</a></span>
</figcaption>
</figure>
<p>The energy for these boosts ultimately comes from an organic compound in the blood called ATP (adenosine triphosphate). This enables electrically charged atoms of sodium and potassium (ions) to be pushed through small channels in the neuron walls, creating electrical voltages which, much like those in silicon transistors, amplify the neuronal electric signals as they travel along the axons.</p>
<p>With 20W of power spread across tens of billions of neurons, the voltages involved are tiny, <a href="https://pubmed.ncbi.nlm.nih.gov/25142940/">as are the axon cables</a>. And there is evidence that axons with a diameter less than about 1 micron (which most in the brain are) are <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2631351/">susceptible to noise</a>. In other words, the brain is a noisy system.</p>
<p>If this noise simply created unhelpful “brain fog”, one might wonder why we evolved to have so many slender axons in our heads. Indeed, there are benefits to having fatter axons: the signals propagate along them faster. If we still needed fast reaction times to escape predators, then slender axons would be <a href="https://www.mpg.de/15409874/axons-cmtm6">disadvantageous</a>. However, developing communal ways of defending ourselves against enemies may have reduced the need for fast reaction times, leading to an evolutionary trend towards thinner axons.</p>
<p>Perhaps, serendipitously, evolutionary mutations that further increased neuron numbers and reduced axon sizes, keeping overall energy consumption the same, made the brain’s neurons more susceptible to noise. And there is mounting evidence that this had another remarkable effect: it encouraged in humans the ability to solve problems that required leaps in imagination and creativity.</p>
<p>Perhaps we only truly became Homo Sapiens when significant noise began to appear in our brains?</p>
<h2>Putting noise in the brain to good use</h2>
<p>Many animals have developed creative approaches to solving problems, but there is nothing to compare with a Shakespeare, a Bach or an Einstein in the animal world.</p>
<p>How do creative geniuses come up with their ideas? Here’s a quote from <a href="https://simonsingh.net/books/fermats-last-theorem/the-whole-story/">Andrew Wiles</a>, perhaps the most famous mathematician alive today, about the time leading up to his celebrated proof of the maths problem (misleadingly) known as Fermat’s Last Theorem:</p>
<blockquote>
<p>When you reach a real impasse, then routine mathematical thinking is of no use to you. Leading up to that kind of new idea, there has to be a long period of tremendous focus on the problem without any distraction. You have to really think about nothing but that problem – just concentrate on it. And then you stop. [At this point] there seems to be a period of relaxation during which the subconscious appears to take over – and it’s during this time that some new insight comes.</p>
</blockquote>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/6ymTZEeTjI8?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">BBC’s Horizon unpicks Andrew Wiles’s novel approach to solving Fermat’s Theorem.</span></figcaption>
</figure>
<p>This notion seems universal. Physics Nobel Laureate <a href="https://sciworthy.com/the-connection-between-black-holes-and-einsteins-theory-of-relativity/#:%7E:text=Penrose%20had%20a%20moment%20of,be%20possible%20in%20all%20systems.">Roger Penrose</a> has spoken about his “Eureka moment” when crossing a busy street with a colleague (perhaps reflecting on their conversation while also looking out for oncoming traffic). For the father of chaos theory <a href="https://www.huffpost.com/entry/imagination-and-the-imagi_b_8178538">Henri Poincaré</a>, it was catching a bus.</p>
<p>And it’s not just creativity in mathematics and physics. Comedian John Cleese, of Monty Python fame, makes much the same point about artistic creativity – it occurs not when you are focusing hard on your trade, but when you relax and let your unconscious mind wander.</p>
<p>Of course, not all the ideas that bubble up from your subconscious are going to be Eureka moments. Physicist Michael Berry <a href="https://michaelberryphysics.files.wordpress.com/2013/06/u8.pdf">talks about</a> these subconscious ideas as if they are elementary particles called “claritons”:</p>
<blockquote>
<p>Actually, I do have a contribution to particle physics … the elementary particle of sudden understanding: the “clariton”. Any scientist will recognise the “aha!” moment when this particle is created. But there is a problem: all too frequently, today’s clariton is annihilated by tomorrow’s “anticlariton”. So many of our scribblings disappear beneath a rubble of anticlaritons.</p>
</blockquote>
<p>Here is something we can all relate to: that in the cold light of day, most of our “brilliant” subconscious ideas get annihilated by logical thinking. Only a very, very, very small number of claritons remain after this process. But the ones that do are likely to be gems.</p>
<p>In his renowned book <a href="https://en.wikipedia.org/wiki/Thinking,_Fast_and_Slow">Thinking Fast and Slow</a>, the Nobel prize-winning psychologist Daniel Kahneman describes the brain in a binary way. Most of the time when walking, chatting and looking around (in other words when multitasking), it operates in a mode Kahneman calls “system 1” – a rather fast, automatic, effortless mode of operation.</p>
<p>By contrast, when we are thinking hard about a specific problem (unitasking), the brain is in the slower, more deliberative and logical “system 2”. To perform a calculation like 37x13, we have to stop walking, stop talking, close our eyes and even put our hands over our ears. No chance for significant multitasking in system 2.</p>
<p>My <a href="https://www.frontiersin.org/articles/10.3389/fncom.2015.00124/full">2015 paper</a> with computational neuroscientist Michael O’Shea interpreted system 1 as a mode where available energy is spread across a large number of active neurons, and system 2 as where energy is focused on a smaller number of active neurons. The amount of energy per active neuron is therefore much smaller when in the system 1 mode, and it would seem plausible that the brain is more susceptible to noise when in this state. That is, in situations when we are multitasking, the operation of any one of the neurons will be most susceptible to the effects of noise in the brain.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/daniel-kahneman-on-noise-the-flaw-in-human-judgement-harder-to-detect-than-cognitive-bias-160525">Daniel Kahneman on 'noise' – the flaw in human judgement harder to detect than cognitive bias</a>
</strong>
</em>
</p>
<hr>
<p>Berry’s picture of clariton-anticlariton interaction seems to suggest a model of the brain where the noisy system 1 and the deterministic system 2 act in synergy. The anticlariton is the logical analysis that we perform in system 2 which, most of the time, leads us to reject our crazy system 1 ideas.</p>
<p>But sometimes one of these ideas turns out to be not so crazy.</p>
<p>This is reminiscent of how our simulated annealing analysis (Figure 1) works. Initially, we might find many “crazy” ideas appealing. But as we get closer to locating the optimal solution, the criteria for accepting a new suggestion becomes more stringent and discerning. Now, system 2 anticlaritons are annihilating almost everything the system 1 claritons can throw at them – but not quite everything, as Wiles found to his great relief.</p>
<h2>The key to creativity</h2>
<p>If the key to creativity is the synergy between noisy and deterministic thinking, what are some consequences of this?</p>
<p>On the one hand, if you do not have the necessary background information then your analytic powers will be depleted. That’s why Wiles says that leading up to the moment of insight, you have to immerse yourself in your subject. You aren’t going to have brilliant ideas which will revolutionise quantum physics unless you have a pretty good grasp of quantum physics in the first place.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/0kSYdOwVi4Y?wmode=transparent&start=1455" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>But you also need to leave yourself enough time each day to do nothing much at all, to relax and let your mind wander. I tell my research students that if they want to be successful in their careers, they shouldn’t spend every waking hour in front of their laptop or desktop. And swapping it for social media probably doesn’t help either, since you still aren’t really multitasking – each moment you are on social media, your attention is still fixed on a specific issue.</p>
<p>But going for a walk or bike ride or painting a shed probably does help. Personally, I find that driving a car is a useful activity for coming up with new ideas and thoughts – provided you don’t turn the radio on.</p>
<p>When making difficult decisions, this suggests that, having listed all the pros and cons, it can be helpful <em>not</em> to actively think about the problem for a while. I think this explains how, years ago, I finally made the decision to change my research direction – not that I knew it at the time.</p>
<p>Because the brain’s system 1 is so energy efficient, we use it to make the vast majority of the many decisions in our daily lives (some say as many as 35,000) – most of which aren’t that important, like whether to continue putting one leg in front of the other as we walk down to the shops. (I could alternatively stop after each step, survey my surroundings to make sure a predator was not going to jump out and attack me, and on that basis decide whether to take the next step.)</p>
<figure class="align-center ">
<img alt="Young man painting a shed" src="https://images.theconversation.com/files/489578/original/file-20221013-19-uwzexe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/489578/original/file-20221013-19-uwzexe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=337&fit=crop&dpr=1 600w, https://images.theconversation.com/files/489578/original/file-20221013-19-uwzexe.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=337&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/489578/original/file-20221013-19-uwzexe.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=337&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/489578/original/file-20221013-19-uwzexe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=423&fit=crop&dpr=1 754w, https://images.theconversation.com/files/489578/original/file-20221013-19-uwzexe.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=423&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/489578/original/file-20221013-19-uwzexe.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=423&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A key part of creative thinking?</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/teenager-has-summer-job-painter-he-2027087039">Blodstrupmoen/Shutterstock</a></span>
</figcaption>
</figure>
<p>However, this system 1 thinking can sometimes lead us to make bad decisions, because we have simply defaulted to this low-energy mode and not engaged system 2 when we should have. How many times do we say to ourselves in hindsight: “Why didn’t I give such and such a decision more thought?”</p>
<p>Of course, if instead we engaged system 2 for every decision we had to make, then we wouldn’t have enough time or energy to do all the other important things we have to do in our daily lives (so the shops may have shut by the time we reach them).</p>
<p>From this point of view, we should not view giving wrong answers to unimportant questions as evidence of irrationality. Kahneman <a href="https://www.semanticscholar.org/paper/Representativeness-revisited%3A-Attribute-in-Kahneman-Frederick/4069615a36c33e61ca309b8ceaeb628a10d441b5?p2df">cites</a> the fact that more than 50% of students at MIT, Harvard and Princeton gave the incorrect answer to this simple question – a bat and ball costs $1.10; the bat costs one dollar more than the ball; how much does the ball cost? – as evidence of our irrationality. The correct answer, if you think about it, <a href="https://www.hitc.com/en-gb/2020/05/31/baseball-bat-and-ball-cost-1-10-riddle-answer-explained/">is 5 cents</a>. But system 1 screams out ten cents.</p>
<p>If we were asked this question on pain of death, one would hope we would spend enough thought to come up with the correct answer. But if we were asked the question as part of an anonymous after-class test, when we had much more important things to spend time and energy doing, then I’d be inclined to think of it as irrational to give the right answer.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-how-does-our-brain-know-to-make-immediate-decisions-155532">Curious Kids: how does our brain know to make immediate decisions?</a>
</strong>
</em>
</p>
<hr>
<p>If we had 20MW to run the brain, we could spend part of it solving unimportant problems. But we only have 20W and we need to use it carefully. Perhaps it’s the 50% of MIT, Harvard and Princeton students who gave the wrong answer who are really the clever ones.</p>
<p>Just as a climate model with noise can produce types of weather that a model without noise can’t, so a brain with noise can produce ideas that a brain without noise can’t. And just as these types of weather can be exceptional hurricanes, so the idea could end up winning you a Nobel Prize.</p>
<p>So, if you want to increase your chances of achieving something extraordinary, I’d recommend going for that walk in the countryside, looking up at the clouds, listening to the birds cheeping, and thinking about what you might eat for dinner.</p>
<h2>So could computers be creative?</h2>
<p>Will computers, one day, be as creative as Shakespeare, Bach or Einstein? Will they understand the world around us as we do? Stephen Hawking <a href="https://www.bbc.co.uk/news/technology-30290540">famously warned</a> that AI will eventually take over and replace mankind.</p>
<p>However, the best-known advocate of the idea that computers will never understand as we do is Hawking’s old colleague, Roger Penrose. In making his claim, Penrose invokes an important “meta” theorem in mathematics known as <a href="https://www.theguardian.com/science/2022/jan/10/can-you-solve-it-godels-incompleteness-theorem#:%7E:text=In%201931%2C%20the%20Austrian%20logician,statements%20that%20cannot%20be%20proved.">Gödel’s theorem</a>, which says there are mathematical truths that can’t be proven by deterministic algorithms.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/hXgqik6HXc0?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>There is a simple way of illustrating Gödel’s theorem. Suppose we make a list of all the most important mathematical theorems that have been proven since the time of the ancient Greeks. First on the list would be <a href="https://www-users.cs.york.ac.uk/susan/cyc/p/primeprf.htm#:%7E:text=Assume%20there%20are%20a%20finite,any%20of%20the%20p%20i%20.">Euclid’s proof</a> that there are an infinite number of prime numbers, which requires one really creative step (multiply the supposedly finite number of primes together and add one). Mathematicians would call this a “trick” – shorthand for a clever and succinct mathematical construction.</p>
<p>But is this trick useful for proving important theorems further down the list, like <a href="https://medium.com/not-zero/two-proofs-of-the-irrationality-of-the-square-root-of-2-fca5c38e44c">Pythagoras’s proof</a> that the square root of two cannot be expressed as the ratio of two whole numbers? It’s clearly not; we need another trick for that theorem. Indeed, as you go down the list, you’ll find that a new trick is typically needed to prove each new theorem. It seems there is no end to the number of tricks that mathematicians will need to prove their theorems. Simply loading a given set of tricks on a computer won’t necessarily make the computer creative. </p>
<p>Does this mean mathematicians can breathe easily, knowing their jobs are not going to be taken over by computers? Well maybe not.</p>
<p>I have been arguing that we need computers to be noisy rather than entirely deterministic, “<a href="https://en.wikipedia.org/wiki/Reproducible_builds">bit-reproducible</a>” machines. And noise, especially if it comes from quantum mechanical processes, would break the assumptions of Gödel’s theorem: a noisy computer is <em>not</em> an algorithmic machine in the usual sense of the word.</p>
<p>Does this imply that a noisy computer can be creative? Alan Turing, pioneer of the general-purpose computing machine, believed this was possible, <a href="https://plato.stanford.edu/entries/turing/#:%7E:text=In%20other%20words%20then%2C%20if,makes%20no%20pretence%20at%20infallibility.">suggesting</a> that “if a machine is expected to be infallible then it cannot also be intelligent”. That is to say, if we want the machine to be intelligent then it had better be capable of making mistakes.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/turing-test-why-it-still-matters-123468">Turing Test: why it still matters</a>
</strong>
</em>
</p>
<hr>
<p>Others may argue there is no evidence that simply adding noise will make an otherwise stupid machine into an intelligent one – and I agree, as it stands. Adding noise to a climate model doesn’t automatically make it an intelligent climate model.</p>
<p>However, the type of synergistic interplay between noise and determinism – the kind that sorts the wheat from the chaff of random ideas – has hardly yet been developed in computer codes. Perhaps we could develop a new type of AI model where the AI is trained by getting it to solve simple mathematical theorems using the clariton-anticlariton model; by making guesses and seeing if any of these have value.</p>
<p>For this to be at all tractable, the AI system would need to be trained to focus on “educated random guesses”. (If the machine’s guesses are all uneducated ones, it will take forever to make progress – like waiting for a group of monkeys to type the first few lines of Hamlet.)</p>
<p>For example, in the context of Euclid’s proof that there are an unlimited number of primes, could we train an AI system in such a way that a random idea like “multiply the assumed finite number of primes together and add one” becomes much more likely than the completely useless random idea “add the assumed finite number of primes together and subtract six”? And if a particular guess turns out to be especially helpful, can we train the AI system so that the next guess is a refinement of the last one? </p>
<p>If we can somehow find a way to do this, it could open up modelling to a completely new level that is relevant to all fields of study. And in so doing, we might yet reach the so-called “<a href="https://en.wikipedia.org/wiki/Technological_singularity">singularity</a>” when machines take over from humans. But only when AI developers fully embrace the constructive role of noise – as it seems the brain did many thousands of years ago.</p>
<p>For now, I feel the need for another walk in the countryside. To blow away some fusty old cobwebs – and perhaps sow the seeds for some exciting new ones.</p>
<hr>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/313478/original/file-20200204-41481-1n8vco4.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/313478/original/file-20200204-41481-1n8vco4.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=112&fit=crop&dpr=1 600w, https://images.theconversation.com/files/313478/original/file-20200204-41481-1n8vco4.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=112&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/313478/original/file-20200204-41481-1n8vco4.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=112&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/313478/original/file-20200204-41481-1n8vco4.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=140&fit=crop&dpr=1 754w, https://images.theconversation.com/files/313478/original/file-20200204-41481-1n8vco4.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=140&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/313478/original/file-20200204-41481-1n8vco4.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=140&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
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</figure>
<p><em>For you: more from our <a href="https://theconversation.com/uk/topics/insights-series-71218?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=InsightsUK">Insights series</a>:</em></p>
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<p class="fine-print"><em><span>Tim Palmer receives funding from The Royal Society and from the European Research Council. His book, The Primacy of Doubt is published by Oxford University Press.
</span></em></p>From more accurate climate modelling to the prospect of truly creative computers, the brain’s use of noise has a lot to teach us.Tim Palmer, Royal Society Research Professor, University of OxfordLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1910432022-10-06T16:30:02Z2022-10-06T16:30:02ZClimate tipping points could lock in unstoppable changes to the planet – how close are they?<figure><img src="https://images.theconversation.com/files/488489/original/file-20221006-18-h17m5t.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C5850%2C2995&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Tipping points in the climate become more likely beyond 1.5°C of warming.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/world-danger-due-economic-environmental-issues-1311948422">Desdemona72/Shutterstock</a></span></figcaption></figure><p>Continued greenhouse gas emissions risk triggering climate tipping points. These are self-sustaining shifts in the climate system that would lock-in devastating changes, like sea-level rise, even if all emissions ended.</p>
<p>The first major assessment in <a href="https://www.pnas.org/doi/10.1073/pnas.0705414105">2008</a> identified nine parts of the climate system that are sensitive to tipping, including ice sheets, ocean currents and major forests. Since then, huge advances in climate modelling and a flood of new observations and records of ancient climate change have given scientists a far better picture of these tipping elements. Extra ones have also been proposed, like permafrost around the Arctic (permanently frozen ground that could unleash more carbon if thawed). </p>
<p>Estimates of the warming levels at which these elements could tip have fallen since 2008. The collapse of the west Antarctic ice sheet was once thought to be a risk when warming reached 3°C-5°C above Earth’s pre-industrial average temperature. Now it’s thought to be <a href="https://www.nature.com/articles/d41586-019-03595-0">possible at current warming levels</a>. </p>
<p>In our <a href="https://www.science.org/doi/10.1126/science.abn7950">new assessment</a> of the past 15 years of research, myself and colleagues found that we can’t rule out five tipping points being triggered right now when global warming stands at roughly 1.2°C. Four of these five become more likely as global warming exceeds 1.5°C.</p>
<p>These are sobering conclusions. Not all of <a href="https://science.altmetric.com/details/135681778/news">the news coverage</a> captured the nuance of our study, though. So here’s what our findings actually mean.</p>
<h2>Uncertain thresholds</h2>
<p>We synthesised the results of more than 200 studies to estimate warming thresholds for each tipping element. The best estimate was either one that multiple studies converged on or which a study judged to be particularly reliable reported. For example, records of when ice sheets had retreated in the past and modelling studies indicate the Greenland ice sheet is likely to collapse beyond 1.5°C. We also estimated the minimum and maximum thresholds at which collapse is possible: model estimates for Greenland range between 0.8°C and 3.0°C.</p>
<figure class="align-center ">
<img alt="A vast wall of blue and white ice with ocean in the foreground." src="https://images.theconversation.com/files/488490/original/file-20221006-14-28qmnr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/488490/original/file-20221006-14-28qmnr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=402&fit=crop&dpr=1 600w, https://images.theconversation.com/files/488490/original/file-20221006-14-28qmnr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=402&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/488490/original/file-20221006-14-28qmnr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=402&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/488490/original/file-20221006-14-28qmnr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=505&fit=crop&dpr=1 754w, https://images.theconversation.com/files/488490/original/file-20221006-14-28qmnr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=505&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/488490/original/file-20221006-14-28qmnr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=505&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Greenland’s ice sheet is showing signs of destabilising at current warming levels.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/diagonal-blue-ice-line-showing-high-793662826">David Dennis/Shutterstock</a></span>
</figcaption>
</figure>
<p>Within this range, tipping becomes more likely as warming increases. We defined tipping as possible (but not yet likely) when warming is above the minimum but below the best estimate, and likely above the best estimate. We also judged how confident we are with each estimate. For example, we are more confident in our estimates for Greenland’s ice sheet collapse than those for abrupt permafrost thaw.</p>
<p>This uncertainty means that we do not expect four climate tipping points to be triggered the first year global temperatures reach 1.5°C (which climate scientists suggest is possible in the next <a href="https://www.metoffice.gov.uk/about-us/press-office/news/weather-and-climate/2022/decadal-forecast-2022">five years</a>), or even when temperatures averaged over several years reach 1.5°C sometime in the next <a href="https://www.carbonbrief.org/analysis-when-might-the-world-exceed-1-5c-and-2c-of-global-warming/">couple of decades</a>. Instead, every fraction of a degree makes tipping more likely, but we can’t be sure exactly when tipping becomes inevitable. </p>
<p>This is especially true for the Greenland and west Antarctic ice sheets. While our assessment suggests their collapse becomes likely beyond 1.5°C, ice sheets are so massive that they change very slowly. Collapse would take thousands of years, and the processes driving it require warming to remain beyond the threshold for several decades. If warming returned below the threshold before tipping kicked in, it may be possible for ice sheets to <a href="https://www.sciencealert.com/disastrous-climate-tipping-points-could-be-reversed-if-we-act-fast">temporarily overshoot their thresholds</a> without collapsing.</p>
<p>For some other tipping points, change is likely to be more dispersed. We estimate that both tropical coral reef death and abrupt permafrost thaw are possible at the current warming level. But thresholds vary between reefs and patches of permafrost. Both are <a href="https://www.nature.com/articles/d41586-019-01313-4">already</a> <a href="https://www.theguardian.com/environment/2022/mar/18/dead-coral-found-at-great-barrier-reef-as-widespread-bleaching-event-unfolds">happening</a> in some places, but in our assessment, these changes become much more widespread at a similar time beyond 1.5°C.</p>
<p>Elsewhere, small patches of the Amazon and northern forests might tip and transition to a savannah-like state <a href="https://www.uu.nl/en/news/climate-change-tipping-points-back-to-the-drawing-table">first</a>, bypassing a more catastrophic dieback across the whole forest. Model <a href="https://egusphere.copernicus.org/preprints/2022/egusphere-2022-82/">results</a> that are yet to be published suggest that <a href="https://climatetippingpoints.info/2021/07/18/amazon-dieback-explainer/">Amazon tipping</a> might occur in several regions at varying warming levels rather than as one big event. </p>
<figure class="align-center ">
<img alt="An aerial view of burning Amazon rainforest surrounded by bare fields." src="https://images.theconversation.com/files/488493/original/file-20221006-19-9tfqka.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/488493/original/file-20221006-19-9tfqka.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=302&fit=crop&dpr=1 600w, https://images.theconversation.com/files/488493/original/file-20221006-19-9tfqka.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=302&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/488493/original/file-20221006-19-9tfqka.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=302&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/488493/original/file-20221006-19-9tfqka.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=379&fit=crop&dpr=1 754w, https://images.theconversation.com/files/488493/original/file-20221006-19-9tfqka.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=379&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/488493/original/file-20221006-19-9tfqka.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=379&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Amazon may not collapse from forest to grassland all at once.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/illegal-fire-burn-forest-trees-amazon-1924644518">Paralaxis/Shutterstock</a></span>
</figcaption>
</figure>
<p>There may also be no well-defined threshold for some tipping elements. Ancient climate records suggest ocean currents in the North Atlantic can dramatically flip from being strong, as they are now, to weak as a result of both warming and melting freshwater from Greenland disrupting circulation. <a href="https://www.sciencealert.com/a-major-ocean-current-might-be-on-the-verge-of-a-climate-change-tipping-point">Recent modelling</a> suggests that the threshold for the collapse of Atlantic circulation depends on how fast warming increases alongside other hard-to-measure factors, making it highly uncertain.</p>
<h2>Into the danger zone</h2>
<p>There are signs that some tipping points are already approaching. Degradation and drought have caused parts of the Amazon to become <a href="https://phys.org/news/2022-03-amazon-rainforest-loss-dieback.html">less resilient</a> to disturbances like fire and <a href="https://www.nature.com/articles/d41586-021-01871-6">emit more carbon</a> than they absorb. </p>
<p>The front edge of some retreating west Antarctic glaciers are <a href="https://blogs.agu.org/geospace/2019/12/04/new-study-models-impact-of-calving-on-retreat-of-thwaites-glacier/">only kilometres away</a> from the unstoppable retreat. Early warning signals in climate monitoring data (such as bigger and longer swings in how much glaciers melt each year) suggest that parts of the <a href="https://physics.aps.org/articles/v14/80">Greenland ice sheet</a> and <a href="https://www.theguardian.com/environment/2021/aug/05/climate-crisis-scientists-spot-warning-signs-of-gulf-stream-collapse">Atlantic circulation</a> are also destabilising.</p>
<p>These signals can’t tell us exactly how close we are to tipping points, only that destabilisation is underway and a tipping point may be approaching. The most we can be sure of is that every fraction of further warming will destabilise these tipping elements more and make the initiation of self-sustaining changes more likely.</p>
<p>This strengthens the case for ambitious emissions cuts in line with the Paris agreement’s aim of halting warming at 1.5°C. This would reduce the chances of triggering multiple climate tipping points – even if we can’t rule out some being reached soon.</p>
<hr>
<figure class="align-right ">
<img alt="Imagine weekly climate newsletter" src="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
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<p class="fine-print"><em><span>David Armstrong McKay is a GSI Visiting Fellow at the University of Exeter and an Associated Researcher at Stockholm Resilience Centre, and is working as a freelance research consultant and science communicator on climate tipping points with the Earth Commission (hosted by non-profit research network Future Earth and is the science component of the Global Commons Alliance, a sponsored project of Rockefeller Philanthropy Advisors, with support from Oak Foundation, MAVA, Porticus, Gordon and Betty Moore Foundation, Herlin Foundation, and the Global Environment Facility) which partially funded this study. His contribution to this study was also funded by the Earth Resilience in the Anthropocene project (European Research Council grant ERC-2016-ADG-743080) and the Leverhulme Trust (RPG-2018-046).</span></em></p>A recent paper suggested damaging climate tipping points could be closer than first thought.David Armstrong McKay, Researcher in Earth System Resilience, Stockholm UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1837012022-05-27T12:07:47Z2022-05-27T12:07:47ZPrehistoric Planet: TV show asked us to explore what weather the dinosaurs lived through<figure><img src="https://images.theconversation.com/files/465730/original/file-20220527-15-z0qxh3.jpg?ixlib=rb-1.1.0&rect=0%2C5%2C3840%2C2149&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.apple.com/uk/tv-pr/originals/prehistoric-planet/episodes-images/">Apple TV+</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-sa/4.0/">CC BY-NC-SA</a></span></figcaption></figure><p>When conjuring up images of when dinosaurs ruled the planet we often think of hot and humid landscapes in a world very different from our own. However, the new TV series <a href="https://tv.apple.com/gb/show/prehistoric-planet/">Prehistoric Planet</a>, narrated by Sir David Attenborough, shows dinosaurs living and indeed thriving in many types of environments, including colder regions where snowstorms, freezing fog and sea-ice were commonplace. </p>
<p>When the show’s producers first approached us to help understand the kinds of weather and environment that dinosaurs lived in before being wiped out around 66 million years ago, it prompted us to tackle a problem that has existed in palaeoclimate modelling for decades. That was, when scientists like us used computers to simulate, or “model”, the climate of prehistoric Earth, the models tended to make the poles much colder than evidence from fossils and rocks suggested they had actually been. </p>
<p>For the TV series, not only have we improved our models, but we have run the computer programmes for longer than anybody else has ever done to get the models as close to ancient “reality” as possible. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/465524/original/file-20220526-16-et19ii.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/465524/original/file-20220526-16-et19ii.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/465524/original/file-20220526-16-et19ii.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/465524/original/file-20220526-16-et19ii.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/465524/original/file-20220526-16-et19ii.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/465524/original/file-20220526-16-et19ii.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/465524/original/file-20220526-16-et19ii.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/465524/original/file-20220526-16-et19ii.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Prehistoric Planet depicts CGI dinosaurs based on the latest research.</span>
<span class="attribution"><span class="source">AppleTV+</span>, <a class="license" href="http://creativecommons.org/licenses/by-nc-sa/4.0/">CC BY-NC-SA</a></span>
</figcaption>
</figure>
<p>The producers, the BBC’s Natural History Unit, needed to know about the weather so they could film “real world” locations similar to those that existed in the past where dinosaurs lived. But most of what we know about the climate that long ago comes from indirect “proxy” evidence, such as leaf fossils and traces of certain chemicals in rocks, which can only reconstruct the average climate over decades or centuries. This is where the narrative of a much hotter and more humid <a href="https://www.science.org/doi/10.1126/science.aay3701">Cretaceous world</a> comes from. </p>
<p>This narrative isn’t exactly wrong, but it doesn’t tell the whole story since weather and climate behave differently. For instance, even in today’s warming world a place like Texas, largely hot and humid, recently experienced <a href="https://www.bbc.co.uk/news/world-us-canada-56076686">widespread snowfall</a>. Geologists a million years from now will spot the sudden global warming – but not the freak snowstorm. Nonetheless, modelling the prehistoric equivalent of these snowstorms is important since we know warmer worlds will experience <a href="https://www.ipcc.ch/sr15/chapter/spm/">greater weather extremes</a>. And these extremes will have largely determined which regions were completely inhospitable to dinosaurs. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/3E0qdExbLTs?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Surface wind speed and precipitation through a typical year 69m years ago. An index of 1 means no visibility beyond 10 metres.</span></figcaption>
</figure>
<h2>How do we know what the weather was like?</h2>
<p>Unfortunately, although fossils give us many clues as to past climate, most cannot directly tell us what the weather was on a day to day basis.</p>
<p>So, for a given place on Earth, how do we know what the weather was on, say, May 27 some 66 million years ago? To do this we need to employ a computer simulation of the climate, similar to the ones used to look at future climate change today. These models are based on <a href="https://gmd.copernicus.org/articles/10/3715/2017/">fundamental physical and biological processes</a> which remain constant with time. It is therefore possible to <a href="https://www.pnas.org/doi/abs/10.1073/pnas.2006087117">adjust them for ancient worlds</a>, even if we don’t know precise details like where or how high the mountains were, or exactly how much carbon dioxide was in the atmosphere.</p>
<p>We can then check these models using some of the ancient climate proxies, such as fossilised leaves, coral or rocks which contain traces of what conditions were like at the time. If our model matches up with the proxies – and it did – then we can be confident it is simulating typical weather at the time.</p>
<p>So what did we learn from modelling the climate of 66m years ago?</p>
<p>Our model found there would have been intense blizzards in Antarctica, for instance, “category six” hurricanes (something we are likely to see in <a href="https://www.theguardian.com/us-news/2018/sep/15/hurricane-category-6-this-is-how-world-ends-book-climate-change">our lifetimes</a>) buffeting the mid and low latitudes and extensive, ever present, fog banks creating murky winters under polar cloud caps. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/ju-_qf8HCmg?wmode=transparent&start=156" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">In a warmer world the water cycle is intensified over the poles. This meant more water in the air, and large parts of the planet would have been very foggy almost all the time (Source: modelling work by the authors)</span></figcaption>
</figure>
<p>This doesn’t immediately sound like a dinosaur-friendly environment. However, the old misconception that dinosaurs were cold blooded, thus requiring a warm climate for survival has for the most part already been dismissed. The new paradigm is that <a href="https://theconversation.com/dinosaurs-how-our-understanding-of-what-they-looked-like-keeps-changing-158937">dinosaurs were warm blooded</a>, and could to some extent regulate their internal temperature, like mammals do today. </p>
<p>This would be essential to survive large swings in temperature, driven by varied weather patterns, particularly in the polar regions. Our modelling therefore backs up recent fossil discoveries which show that some dinosaur species were cold-adapted, could see in <a href="https://www.smithsonianmag.com/science-nature/how-dinosaurs-thrived-snow-180976435/#:%7E:text=%E2%80%9CThere%20would%20have%20been%20ice,body%20size%20of%20any%20dinosaur.">low light conditions</a> (useful in those huge fog banks), and thrived year-round near the poles.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/465517/original/file-20220526-14-l6p8n4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Dinosaur in snow" src="https://images.theconversation.com/files/465517/original/file-20220526-14-l6p8n4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/465517/original/file-20220526-14-l6p8n4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/465517/original/file-20220526-14-l6p8n4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/465517/original/file-20220526-14-l6p8n4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/465517/original/file-20220526-14-l6p8n4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/465517/original/file-20220526-14-l6p8n4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/465517/original/file-20220526-14-l6p8n4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption"><em>Pachyrhinosaurus</em> surviving and thriving.</span>
<span class="attribution"><span class="source">AppleTV+</span>, <a class="license" href="http://creativecommons.org/licenses/by-nc-sa/4.0/">CC BY-NC-SA</a></span>
</figcaption>
</figure>
<p>The Prehistoric Planet scenes with the chilly <a href="https://www.youtube.com/watch?v=eQah4McU2ww"><em>Pachyrhinosaurus</em></a> were set in Alaska, and demonstrate why the show wanted check its accuracy with climate models. We have an idea what the conditions would have been like there 66m years ago thanks to detailed fossils of plants, dinosaurs and other animals, yet the old models would have predicted intensely-cold and lifeless tundra. </p>
<p>Our model instead matches up with the fossil evidence, and predicts forests right up to the margins of the Arctic Ocean at 82°N – much further north than any trees today. In the summer, dinosaur food would have been abundant, but in the long dark winters it would have been more difficult to find, particularly as both fossils and modelling suggests it was so foggy. </p>
<p>Dinosaurs survived for a remarkable 165 million years. <em>Tyrannosaurus Rex</em> lived much closer to present day humans than it did to <em>Stegosauruses</em>, for instance. They managed to survive so long because they were resilient and adaptable to changeable environmental conditions, much like mammals are today. Our work for Prehistoric Planet shows that they were able to survive through greater extremes in temperature, stormier weather, and more extreme droughts than humans have experienced – so far.</p><img src="https://counter.theconversation.com/content/183701/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alex Farnsworth works for the University of Bristol and consults for the BBC and receives funding from NERC and The Leverhulme Trust. </span></em></p><p class="fine-print"><em><span>Paul Valdes works at the University of Bristol. He was consultant for the BBC and receive funding from NERC, Leverhulme, and the EU (via their Horizon 2220 program).</span></em></p><p class="fine-print"><em><span>Robert Spicer is a consultant for the BBC. He receives funding from the Natural Environment Research Council and the Chinese Academy of Sciences. </span></em></p>Yes, dinosaurs really did survive in snow – we simulated the Cretaceous climate to prove it.Alex Farnsworth, Senior Research Associate in Meteorology, University of BristolPaul Valdes, Professor of Physical Geography, University of BristolRobert Spicer, Emeritus Professor of Earth Sciences, The Open UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1759362022-01-28T16:17:52Z2022-01-28T16:17:52ZThree reasons why climate change models are our best hope for understanding the future<figure><img src="https://images.theconversation.com/files/443179/original/file-20220128-21-3qlehw.jpg?ixlib=rb-1.1.0&rect=1413%2C0%2C4165%2C3997&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/abstraction-earth-puzzle-pieces-falling-off-42186811">Dan Moeller/Shutterstock</a></span></figcaption></figure><p>It’s <a href="https://theconversation.com/the-five-corrupt-pillars-of-climate-change-denial-122893">a common argument</a> among climate deniers: scientific models cannot predict the future, so why should we trust them to tell us how the climate will change?</p>
<p>This trope recently surfaced in an interview with Canadian psychologist and author Jordan Peterson on Joe Rogan’s podcast. <a href="https://twitter.com/thebadstats/status/1486103450446303234?s=20&t=Ez5UpHJgtKfes9FYTdw6Fg">According to Peterson</a>: “There is no such thing as climate… climate and everything are the same word.” Faced with the impossible task of including “everything” in their equations – and predicting what will happen weeks and months from now – the world’s scientists are incapable of modelling the climate accurately, in Peterson’s view.</p>
<p>As a scientist whose research involves modelling the climate on a global and regional scale, I can say with confidence that this interpretation is wrong. Here are just three reasons why. </p>
<h2>Muddling weather and climate</h2>
<p>Deniers often <a href="https://global.oup.com/academic/product/climate-a-very-short-introduction-9780199641130?cc=gb&lang=en&">confuse the climate with weather</a> when arguing that models are inherently inaccurate. Weather refers to the short-term conditions in the atmosphere at any given time. The climate, meanwhile, is the weather of a region averaged over several decades.</p>
<figure class="align-center ">
<img alt="A computer-generated weather map showing pressure systems with lines and colours." src="https://images.theconversation.com/files/443145/original/file-20220128-21-kn64wl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/443145/original/file-20220128-21-kn64wl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=350&fit=crop&dpr=1 600w, https://images.theconversation.com/files/443145/original/file-20220128-21-kn64wl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=350&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/443145/original/file-20220128-21-kn64wl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=350&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/443145/original/file-20220128-21-kn64wl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=440&fit=crop&dpr=1 754w, https://images.theconversation.com/files/443145/original/file-20220128-21-kn64wl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=440&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/443145/original/file-20220128-21-kn64wl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=440&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Forecasting the weather is quite different from modelling the climate.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-illustration/weather-map-3d-rendering-1123177739">Andrey VP/Shutterstock</a></span>
</figcaption>
</figure>
<p>Weather predictions have got much <a href="https://theconversation.com/why-the-weather-forecast-will-always-be-a-bit-wrong-101547">more accurate</a> over the last 40 years, but the chaotic nature of weather means they become unreliable beyond a week or so. Modelling climate change is much easier however, as you are dealing with long-term averages. For example, we know the weather will be warmer in summer and colder in winter. </p>
<p>Here’s a helpful comparison. It is impossible to predict at what age any particular person will die, but we can say with a high degree of confidence what the average life expectancy of a person will be in a particular country. And we can say with 100% confidence that they will die. Just as we can say with absolute certainty that putting greenhouses gases in the atmosphere warms the planet.</p>
<h2>Strength in numbers</h2>
<p>There are a huge range of <a href="https://www.carbonbrief.org/timeline-history-climate-modelling">climate models</a>, from those attempting to understand specific mechanisms such as <a href="https://theconversation.com/why-clouds-are-the-missing-piece-in-the-climate-change-puzzle-140812">the behaviour of clouds</a>, to general circulation models (GCM) that are used to predict the future climate of our planet. </p>
<p>There are over 20 major <a href="https://www.carbonbrief.org/qa-how-do-climate-models-work">international research centres</a> where teams of some of the smartest people in the world have built and run these GCMs which contain millions of lines of code representing the very latest understanding of the climate system. These models are continually tested against historic and palaeoclimate data (this refers to climate data from well before direct measurements, like the last ice age), as well as individual climate events such as large volcanic eruptions to make sure they reconstruct the climate, which they do extremely well.</p>
<p>No single model should ever be considered complete as they represent a very complex global climate system. But having so many different models constructed and calibrated independently means that scientists can be confident <a href="https://rgs-ibg.onlinelibrary.wiley.com/doi/full/10.1111/j.1475-4959.2012.00494.x">when the models agree</a>. </p>
<p>Model predictions from the 1970s and 1980s compare stunningly well with the warming trend that actually occurred over the last four decades. And scientists have been continually testing and improving these models ever since, meaning their predictions are a very robust outcome of our science.</p>
<figure class="align-center ">
<img alt="A line graph showing the range of model predictions and the actual temperature record since 1980." src="https://images.theconversation.com/files/443140/original/file-20220128-15-pet4aa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/443140/original/file-20220128-15-pet4aa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=361&fit=crop&dpr=1 600w, https://images.theconversation.com/files/443140/original/file-20220128-15-pet4aa.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=361&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/443140/original/file-20220128-15-pet4aa.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=361&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/443140/original/file-20220128-15-pet4aa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=454&fit=crop&dpr=1 754w, https://images.theconversation.com/files/443140/original/file-20220128-15-pet4aa.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=454&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/443140/original/file-20220128-15-pet4aa.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=454&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">How the earliest climate models compared with reality.</span>
<span class="attribution"><a class="source" href="https://global.oup.com/academic/product/climate-change-a-very-short-introduction-9780198867869?cc=gb&lang=en&">Mark Maslin/Oxford University Press</a>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Errors about error</h2>
<p>Given the climate is such a complicated system, you might reasonably ask how scientists address potential sources of error, especially when modelling the climate over hundreds of years.</p>
<p>The biggest source of uncertainty in all climate change models is how much greenhouse gases humanity will emit over the next 80 years. Scientists account for this by working with economists and social scientists to build scenarios of the future with different emissions trajectories. </p>
<p>We scientists are very aware that models are simplifications of a complex world. But by having so many different models, built by different groups of experts, we can be more certain of the results they produce. All the models show the same thing: put greenhouses gases into the atmosphere and the world warms up. We represent the potential errors by showing the range of warming produced by all the models for each scenario.</p>
<p>In its <a href="https://theconversation.com/this-is-the-most-sobering-report-card-yet-on-climate-change-and-earths-future-heres-what-you-need-to-know-165395">sixth assessment</a> of the science of climate change, published in August 2021, the Intergovernmental Panel on Climate Change stated that “it is unequivocal that human influence has warmed the atmosphere, ocean and land”. How human activity will continue to affect the climate is a difficult question primarily because we do not know how the world will respond to this crisis. But we can count on models, which have a proven record of accuracy, to help us navigate what the future is likely to hold.</p>
<p>What is most worrying about this kind of climate change denial is that it still gets airtime. Shows like The Joe Rogan Experience can host guests peddling misinformation about climate change or the pandemic just to get a ratings boost. Spotify, <a href="https://www.wsj.com/articles/spotify-strikes-exclusive-podcast-deal-with-joe-rogan-11589913814">it’s reported</a>, paid US$100 million (£75 million) for Rogan’s podcast in 2020 and the platform has <a href="https://www.independent.co.uk/climate-change/news/joe-rogan-jordan-peterson-spotify-b2001368.html">over 380 million users</a>. Joe Rogan surely does not need a bigger audience or a bigger pay packet, so why not have credible experts on who actually want to help build a better, safer, and healthier world? This is what listeners want to hear about – real problems, real facts, real solutions.</p>
<hr>
<figure class="align-right ">
<img alt="Imagine weekly climate newsletter" src="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
</figcaption>
</figure>
<p><strong><em>Don’t have time to read about climate change as much as you’d like?</em></strong>
<br><em><a href="https://theconversation.com/uk/newsletters/imagine-57?utm_source=TCUK&utm_medium=linkback&utm_campaign=Imagine&utm_content=DontHaveTimeTop">Get a weekly roundup in your inbox instead.</a> Every Wednesday, The Conversation’s environment editor writes Imagine, a short email that goes a little deeper into just one climate issue. <a href="https://theconversation.com/uk/newsletters/imagine-57?utm_source=TCUK&utm_medium=linkback&utm_campaign=Imagine&utm_content=DontHaveTimeBottom">Join the 10,000+ readers who’ve subscribed so far.</a></em></p>
<hr><img src="https://counter.theconversation.com/content/175936/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mark Maslin is a Founding Director of Rezatec Ltd, Co-Director of The London NERC Doctoral Training Partnership, a member of Cheltenham Science Festival Advisory Committee and a member of the Climate Crisis Advisory Group. He is an unpaid member of the Sopra-Steria CSR Board, Sheep Included Ltd and NetZeroNow Advisory Boards. He has received grant funding in the past from the NERC, EPSRC, ESRC, DFG, Royal Society, DIFD, BEIS, DECC, FCO, Innovate UK, Carbon Trust, UK Space Agency, European Space Agency, Research England, Wellcome Trust, Leverhulme Trust, The Children's Investment Fund Foundation Sprint2020, and British Council. He has received research funding in the past from The Lancet, Laithwaites, Seventh Generation, Channel 4, JLT Re, WWF, Hermes, CAFOD, HP, and Royal Institute of Chartered Surveyors.</span></em></p>Climate models from the 1970s and 80s stand up incredibly well when compared with actual warming trends.Mark Maslin, Professor of Earth System Science, UCLLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1757662022-01-27T13:27:24Z2022-01-27T13:27:24ZCoffee may become more scarce and expensive thanks to climate change – new research<figure><img src="https://images.theconversation.com/files/442956/original/file-20220127-6942-n58tvo.jpg?ixlib=rb-1.1.0&rect=0%2C333%2C2448%2C1363&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Colombia's coffee region: the country could lose two thirds of its best coffee-growing land.</span> <span class="attribution"><span class="source">Javier Crespo / shutterstock</span></span></figcaption></figure><p>The world could lose half of its best coffee-growing land under a moderate climate change scenario. Brazil, which is the currently world’s largest coffee producer, will see its most suitable coffee-growing land decline by 79%. </p>
<p>That’s one key finding of a <a href="https://journals.plos.org/plosone/article/authors?id=10.1371/journal.pone.0261976">new study</a> by scientists in Switzerland, who assessed the potential impacts of climate change on coffee, cashews and avocados. All three are important globally traded crops that are mainly produced by small-scale farmers in the tropics. </p>
<p>Coffee is by far the most important with an expected revenue of <a href="https://www.statista.com/outlook/cmo/hot-drinks/coffee/worldwide">US$460 billion (£344 billion) in 2022</a>, while the figures for avocado and cashew are respectively $13 billion and $6 billion. While coffee mainly serves as a stimulatory beverage, avocados and cashews are widely consumed food crops that are rich in monounsaturated plant oils and other <a href="https://kale.world/avocado-oil-vs-cashews/">beneficial nutrients</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/442960/original/file-20220127-18-10nf2eg.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Map of suitable coffee growing regions" src="https://images.theconversation.com/files/442960/original/file-20220127-18-10nf2eg.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/442960/original/file-20220127-18-10nf2eg.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=299&fit=crop&dpr=1 600w, https://images.theconversation.com/files/442960/original/file-20220127-18-10nf2eg.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=299&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/442960/original/file-20220127-18-10nf2eg.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=299&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/442960/original/file-20220127-18-10nf2eg.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=376&fit=crop&dpr=1 754w, https://images.theconversation.com/files/442960/original/file-20220127-18-10nf2eg.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=376&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/442960/original/file-20220127-18-10nf2eg.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=376&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Coffee requires a tricky mix of climate, land and soil conditions and can’t just be grown anywhere in the tropics.</span>
<span class="attribution"><a class="source" href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0261976#sec002">Grüter et al / PLOS</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>The major take-home message from the new study is that predicted climatic changes are likely to result in significant declines in the amount of land suitable for growing these crops in some of the main regions where they are currently cultivated. In turn this could impact both growers and consumers around the world.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/442962/original/file-20220127-16-3ucnf2.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Map of coffee suitability change by 2050" src="https://images.theconversation.com/files/442962/original/file-20220127-16-3ucnf2.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/442962/original/file-20220127-16-3ucnf2.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=299&fit=crop&dpr=1 600w, https://images.theconversation.com/files/442962/original/file-20220127-16-3ucnf2.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=299&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/442962/original/file-20220127-16-3ucnf2.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=299&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/442962/original/file-20220127-16-3ucnf2.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=376&fit=crop&dpr=1 754w, https://images.theconversation.com/files/442962/original/file-20220127-16-3ucnf2.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=376&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/442962/original/file-20220127-16-3ucnf2.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=376&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Many areas will become less suitable for coffee if there is moderate climate change (neither worst nor best-case emissions scenario).</span>
<span class="attribution"><a class="source" href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0261976#sec002">Grüter et al / PLOS</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>To date, most research into the future impacts of climate change on food has focused on principal staple crops such as wheat, maize, potatoes and oilseeds that are grown in temperate regions. This has mirrored the tendency of climate scientists to focus on the potentially severe impacts of climate change on temperate ecosystems, especially due to altered temperature and rainfall patterns. </p>
<p>In contrast, there has been <a href="https://www.science.org/content/article/expanding-tropics-will-play-greater-global-role-report-predicts">less work on the tropical ecosystems</a> that constitute about 40% of global land area where more than 3 billion people make their living, with as many as <a href="https://worldpopulationreview.com/country-rankings/tropical-countries">1 billion more people</a> expected to do so by the 2050s.</p>
<p>The tropics also sustain vast reservoirs of biodiversity, as well as areas to <a href="https://www.nature.com/articles/s43016-020-0076-z">grow many important crops</a> that provide income and food for their huge human populations. The new research confirms and significantly extends findings from the relatively small number of existing studies on coffee, cashew and avocado crops. </p>
<p>An important innovation in the study is to examine land and soil parameters in addition to purely climatic factors such as temperature and rainfall patterns. This enables them to provide a more nuanced view of future impacts that might significantly change the suitability of some tropical regions for growing certain crops due to changes in factors such as soil pH or texture.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/442968/original/file-20220127-7574-wtn5j5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Man tosses coffee beans on a plantation" src="https://images.theconversation.com/files/442968/original/file-20220127-7574-wtn5j5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/442968/original/file-20220127-7574-wtn5j5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/442968/original/file-20220127-7574-wtn5j5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/442968/original/file-20220127-7574-wtn5j5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/442968/original/file-20220127-7574-wtn5j5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/442968/original/file-20220127-7574-wtn5j5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/442968/original/file-20220127-7574-wtn5j5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Different factors limit the coffee-suitability of different regions. The Amazon basin has a suitable climate but the soil is too acidic.</span>
<span class="attribution"><span class="source">Jair Ferreira Belafacce / shutterstock</span></span>
</figcaption>
</figure>
<p>The new study complements other recent research into oil palm. Though controversial and often <a href="https://theconversation.com/growing-palm-oil-on-former-farmland-cuts-deforestation-co-and-biodiversity-loss-127312">linked to deforestation</a>, oil palm is still one of the most important tropical crops in terms of human nutrition, helping feed more than 3 billion people. </p>
<p>Colleagues and I recently reviewed several modelling analyses of how climate change could impact the <a href="https://cabiagbio.biomedcentral.com/articles/10.1186/s43170-021-00058-3">incidence of disease and overall mortality in oil palm</a>. The stark conclusion was that tree mortality is likely to increase significantly after 2050, possibly wiping out much of the crop in the Americas. In addition, incidence of the major stem rot disease was predicted to increase drastically across south-east Asia.</p>
<h2>Surprising extent and complexity</h2>
<p>Collectively, these studies are beginning to reveal the surprising extent and complexity of the impacts of climate change and associated factors on some of the most grown crops in the tropics. Importantly, the impacts will not be distributed evenly and some regions might even benefit from climate change. </p>
<p>For instance, parts of China, Argentina and the US are likely to become more suitable for coffee growing just as the likes of Brazil and Colombia see their land become less suitable. It is likely that many of these changes are now “locked in” at least for the rest of this century, irrespective of the <a href="https://theconversation.com/the-ultimate-guide-to-why-the-cop26-summit-ended-in-failure-and-disappointment-despite-a-few-bright-spots-171723">disappointingly sluggish response of global leaders</a> in terms of reducing greenhouse gas emissions.</p>
<p>Therefore, it will be necessary for us to adapt to the ongoing changes in the tropics, for example by shifting cultivation of specific crops to different regions where climate impacts will be more benign. However, it seems likely that, whatever mitigation measures are adopted, many tropical crops will become scarcer and hence more expensive in the future. In terms of coffee, it might even move from a cheap everyday beverage to a <a href="https://wineeconomist.com/2009/10/19/cracking-the-coffee-wine-paradox/">prized treat</a> to be sampled on special occasions, rather like a fine wine.</p>
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<img alt="Imagine weekly climate newsletter" src="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p><strong><em>Don’t have time to read about climate change as much as you’d like?</em></strong>
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<p class="fine-print"><em><span>Denis J Murphy does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>More than half of the world’s best growing land could become less suited for coffee.Denis J Murphy, Professor of Biotechnology, Head of Genomics & Computational Biology Research, University of South WalesLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1719022021-12-09T15:03:48Z2021-12-09T15:03:48ZDune: how high could giant sand dunes actually grow on Arrakis?<p>Frank Herbert first published his science-fiction epic Dune back in 1965, though its origins lay in a chance encounter eight years previously when as a journalist he was tasked to report on a dune stabilisation programme in the US state of Oregon. Ultimately, this set the wheels in motion for the recent film adaptation.</p>
<p>The large and inhospitable sand dunes of the desert planet Arrakis are, of course, very prominent in both the books and film, not least because of the terrifying gigantic sandworms that hunt any movement on the surface. But just how high would sand dunes be on a realistic version of this world? </p>
<p>Before the movie was released, we took a scientific climate model and used it to <a href="https://theconversation.com/dune-we-simulated-the-desert-planet-of-arrakis-to-see-if-humans-could-survive-there-170181">simulate the climate of Arrakis</a>. We now want to use insights from this same model to focus on the dunes themselves. </p>
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Read more:
<a href="https://theconversation.com/dune-we-simulated-the-desert-planet-of-arrakis-to-see-if-humans-could-survive-there-170181">Dune: we simulated the desert planet of Arrakis to see if humans could survive there</a>
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<p>Sand dunes are the product of thousands or even tens of thousands of years of erosion of the underlying or surrounding geology. On a simple level, they are formed by sand being blown along the path of the prevailing wind until it meets an obstruction, at which point the sand will settle in front of it. </p>
<p>There is certainly no shortage of wind on Arrakis. Our simulation showed that wind would routinely exceed the minimum speed required to blow sand grains into the air, and there are even some regions where speeds regularly reach 162 km/h during the year. That’s well over hurricane force. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/436657/original/file-20211209-136652-ardcx5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Diagram of sand dune formation" src="https://images.theconversation.com/files/436657/original/file-20211209-136652-ardcx5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/436657/original/file-20211209-136652-ardcx5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=188&fit=crop&dpr=1 600w, https://images.theconversation.com/files/436657/original/file-20211209-136652-ardcx5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=188&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/436657/original/file-20211209-136652-ardcx5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=188&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/436657/original/file-20211209-136652-ardcx5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=236&fit=crop&dpr=1 754w, https://images.theconversation.com/files/436657/original/file-20211209-136652-ardcx5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=236&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/436657/original/file-20211209-136652-ardcx5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=236&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">How sand dunes are formed.</span>
<span class="attribution"><span class="source">David Tarailo / US National Park Service / Geological Society of America</span></span>
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</figure>
<p>Sand dunes in the book are said to be on average around 100 metres high. However, this isn’t based on actual science, more likely it’s what Herbert knew from his time in Oregon as well as the world we live in. But we can use our climate model to predict what the general (and maximum) attainable height might suggest.</p>
<h2>Where the wind blows</h2>
<p>The size and distance between giant dunes are determined not simply by the type of sand or underlying rock, but by the lowest 2km or so of the atmosphere that interacts with the land surface. This level, also known as the planetary boundary layer, is where most of the weather we can see occurs. Above this, a thin “inversion layer” separates the weather below from the more stable higher-altitude part of the atmosphere.</p>
<p>The growth of sand dunes and theoretical height is determined by the depth of this boundary layer where the wind blows. Sand dunes stabilise above the wind at the altitude of the inversion layer. The height of the boundary layer – usually somewhere between 100 metres to 2,000 metres – can <a href="https://journals.ametsoc.org/view/journals/atsc/31/5/1520-0469_1974_031_1297_almotu_2_0_co_2.xml">vary through the night as well as the year</a>. When it is cooler, it is shallower. When there is a strong wind or lots of rising warm air, it is deeper. </p>
<p>Arrakis would be much hotter than Earth, which means more rising air and a boundary layer two to three times as high over land compared with ours. Our climate model simulation, therefore, predicts dunes on Arrakis would be as high as 250m, particularly in the tropics and mid-latitudes. That’s about three times the height of the Big Ben clock tower in London. Most regions would have a more modest average height of between 25m and 75m. As the boundary layer is generally higher everywhere on Arrakis the average dune height is in general twice that of Earths.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/436660/original/file-20211209-138695-ijn7ax.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="map with shaded areas" src="https://images.theconversation.com/files/436660/original/file-20211209-138695-ijn7ax.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/436660/original/file-20211209-138695-ijn7ax.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=425&fit=crop&dpr=1 600w, https://images.theconversation.com/files/436660/original/file-20211209-138695-ijn7ax.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=425&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/436660/original/file-20211209-138695-ijn7ax.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=425&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/436660/original/file-20211209-138695-ijn7ax.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=534&fit=crop&dpr=1 754w, https://images.theconversation.com/files/436660/original/file-20211209-138695-ijn7ax.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=534&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/436660/original/file-20211209-138695-ijn7ax.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=534&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Predicted sand dune height (in metres) on Arrakis.</span>
<span class="attribution"><span class="source">Farnsworth et al</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>We were also able to simulate the space between dunes, which can also be determined by the height of the boundary layer. Spacing is highest in the tropics, a little over 2km between the crest of one giant sand dune to the next. However, in general, sand dunes have a spacing of around 0.5 to 1km crest to crest. Still plenty of room for a sandworm to wiggle through. Scientists looking at Saturn’s moon Titan have run this same process in reverse, using the space between dunes – easy to measure with satellite images – to estimate a <a href="https://www.researchgate.net/publication/222551737_A_3km_atmospheric_boundary_layer_on_Titan_indicated_by_dune_spacing_and_Huygens_data">boundary layer of up to 3km</a>.</p>
<p>As nothing can grow on Arrakis to stabilise these sand dunes they will always be in a state of constant drift across the planet. Some large dunes on Earth can move about 5m a year. Smaller dunes can move even faster – about 20m a year.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/427871/original/file-20211021-15766-1q37jmx.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/427871/original/file-20211021-15766-1q37jmx.gif?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=429&fit=crop&dpr=1 600w, https://images.theconversation.com/files/427871/original/file-20211021-15766-1q37jmx.gif?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=429&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/427871/original/file-20211021-15766-1q37jmx.gif?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=429&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/427871/original/file-20211021-15766-1q37jmx.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=539&fit=crop&dpr=1 754w, https://images.theconversation.com/files/427871/original/file-20211021-15766-1q37jmx.gif?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=539&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/427871/original/file-20211021-15766-1q37jmx.gif?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=539&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A visualisation of the authors’ climate model of Arrakis. Source: climatearchive.org/dune.</span>
</figcaption>
</figure>
<h2>Mountain-sized dunes?</h2>
<p>Our simulation can only give the general height that most sand dunes would reach, and there would be exceptions to the rule. For instance, the largest known sand dune on Earth today is the Duna Federico Kirbus in Argentina, a staggering 1,234m in height. Its size shows that local factors, such as vegetation, surrounding hills or the type of local sand, can play an important role. </p>
<p>Given Arrakis is hotter than Earth, has a higher boundary layer and has more sand and stronger winds, it’s possible a truly mammoth dune the size of a small mountain may form somewhere – it’s just impossible for a climate model to say exactly where. </p>
<p>Scientists have recently revealed that as the world warms the planetary boundary layer is increasing by around <a href="https://www.newscientist.com/article/2296500-lowest-level-of-the-atmosphere-getting-thicker-due-to-climate-change/">53 metres a decade</a>. So we may well see even bigger record-breaking sand dunes as the lower atmosphere continues to warm – even if Earth will not end up like Arrakis.</p><img src="https://counter.theconversation.com/content/171902/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alex Farnsworth receives funding from UK Research and Innovation. He is affiliated with the Institute of Tibetan Plateau Research (ITP), Chinese Academy of Sciences.</span></em></p><p class="fine-print"><em><span>Sebastian Steinig receives funding from the Natural Environment Research Council and has been supported by the Jean Golding Institute for data science and data-intensive research at the University of Bristol.</span></em></p><p class="fine-print"><em><span>Michael Farnsworth does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>We simulated the desert planet to find out.Alex Farnsworth, Senior Research Associate in Meteorology, University of BristolMichael Farnsworth, Research Lead Future Electrical Machines Manufacturing Hub, University of SheffieldSebastian Steinig, Research Associate in Paleoclimate Modelling, University of BristolLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1724822021-11-25T19:03:25Z2021-11-25T19:03:25ZEven if we halt global warming, local climates will change – and we need new experiments to understand how<figure><img src="https://images.theconversation.com/files/433828/original/file-20211125-17-19ry8x7.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C3834%2C2149&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>There’s a big question mark over whether the world will keep global warming below the limits set out in the Paris Agreement. But even if we do, the climate will keep evolving – and society needs to prepare for this.</p>
<p>At the moment, climate models don’t tell us much about a future world in which temperatures have stabilised. As our <a href="https://dx.doi.org/10.1038/s41558-021-01225-0">research</a> published today argues, new model experiments are needed to close this knowledge gap and better understand the challenges ahead. </p>
<p>For example, in southern Australia, climate change has already caused a <a href="https://theconversation.com/climate-change-is-likely-driving-a-drier-southern-australia-so-why-are-we-having-such-a-wet-year-172409">trend</a> towards less rain and more frequent and prolonged drought. If the global climate stabilises, we expect this drying trend to reverse, which could ease future strains on water supply in this region. This would in turn affect urban planning, agriculture and water policy. </p>
<p>The new models we’re proposing would enable more useful climate projections aligned with the Paris Agreement targets – and better prepare society for a warmer, but more stable, global temperature.</p>
<h2>Targeting a stable climate</h2>
<p>Under the landmark Paris Agreement, the world is aiming to keep global warming well below 2°C compared with <a href="https://theconversation.com/what-is-a-pre-industrial-climate-and-why-does-it-matter-78601">pre-industrial</a> times, and preferably below 1.5°C.</p>
<p>The world is warming at a rate of around 0.25°C per decade and is already about <a href="https://www.globalwarmingindex.org/">1.2°C warmer</a> than in pre-industrial times. </p>
<p>This warming won’t stop until net greenhouse gas emissions are <a href="https://www.carbonbrief.org/explainer-will-global-warming-stop-as-soon-as-net-zero-emissions-are-reached">near zero</a>. If we don’t greatly reduce emissions in the next decade, we will warm the planet beyond 1.5°C.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/433635/original/file-20211124-24-c6db8t.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/433635/original/file-20211124-24-c6db8t.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=223&fit=crop&dpr=1 600w, https://images.theconversation.com/files/433635/original/file-20211124-24-c6db8t.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=223&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/433635/original/file-20211124-24-c6db8t.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=223&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/433635/original/file-20211124-24-c6db8t.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=280&fit=crop&dpr=1 754w, https://images.theconversation.com/files/433635/original/file-20211124-24-c6db8t.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=280&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/433635/original/file-20211124-24-c6db8t.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=280&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The world has warmed and will continue to warm in the coming decades but the Paris Agreement targets a stabilised future climate with low global warming.</span>
<span class="attribution"><span class="source">Author provided</span></span>
</figcaption>
</figure>
<p>To date, climate simulations used to examine the implications of the Paris Agreement either assume warming continues beyond 1.5°C and 2°C, or only examine a short period after warming has stopped. This is because most of these simulations were not specifically designed to analyse global warming levels linked to the Paris Agreement, and mostly focus only on what will happen this century.</p>
<p>If we manage to stabilise global temperatures, other aspects of Earth’s climate would continue to change. Studies based on <a href="https://journals.ametsoc.org/view/journals/bams/100/12/bams-d-19-0068.1.xml">long model experiments</a> suggest ocean and land temperatures continue to evolve for centuries after global warming slows. That’s because the ocean warms at a slower rate than the land, and warming water can take hundreds, and even thousands, of years to mix into the deep ocean.</p>
<p>Even after the global temperature stabilises at the levels set out in the Paris Agreement, many ocean areas would likely warm by at least a further 0.5°C. Meanwhile some land areas would cool by <a href="https://pursuit.unimelb.edu.au/articles/how-fast-the-planet-warms-will-be-crucial-for-liveability">at least 0.5°C</a>.</p>
<p>The ocean takes time to catch up – and as it does, land temperatures have to fall to maintain the same global average temperature.</p>
<p>In addition, if global temperature remained near-constant, rainfall patterns would likely <a href="https://www.nature.com/articles/s41558-019-0397-9">change</a>. In some subtropical regions, such as southern Australia, this might mean a reversal of the drying trends we’ve seen over the past few decades.</p>
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Read more:
<a href="https://theconversation.com/yes-a-few-climate-models-give-unexpected-predictions-but-the-technology-remains-a-powerful-tool-165611">Yes, a few climate models give unexpected predictions – but the technology remains a powerful tool</a>
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<figure class="align-center ">
<img alt="man stands on ice looking at Arctic scene" src="https://images.theconversation.com/files/433830/original/file-20211125-27-1wn5fny.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/433830/original/file-20211125-27-1wn5fny.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/433830/original/file-20211125-27-1wn5fny.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/433830/original/file-20211125-27-1wn5fny.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/433830/original/file-20211125-27-1wn5fny.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/433830/original/file-20211125-27-1wn5fny.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/433830/original/file-20211125-27-1wn5fny.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">The ocean takes time to catch up to global warming.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
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</figure>
<h2>New models are needed</h2>
<p>Clearly, we need new experiments to model Earth’s climate if warming is stabilised at 1.5°C. Our <a href="https://dx.doi.org/10.1038/s41558-021-01225-0">new paper</a> proposes a framework for designing these experiments.</p>
<p>Our framework differs from the approach taken by various climate modelling groups around the world in recent decades. </p>
<p>These groups have all used the same projection of greenhouse gas concentrations in the atmosphere, and how they change through time. This <a href="https://gmd.copernicus.org/articles/9/3461/2016/gmd-9-3461-2016.pdf">approach</a> allows for comparison of climate projections between models for the same greenhouse gas scenarios.</p>
<p>But because each group fed this projection into their own climate model – each with their own characteristics – each produced different predictions for how much global warming would occur. Also, these model simulations are mostly run only to 2100, and so represent a world that’s continuing to warm and hasn’t had time to stabilise.</p>
<p>Instead, our framework involves reaching the same level of global warming across a range of climate models. This would be achieved by “turning off” the carbon emissions used in various climate models at different times. </p>
<p>So, a climate model that warms more strongly in response to greenhouse gas emissions would have its carbon emissions “turned off” earlier, relative to a slower warming model. This would provide a group of climate model simulations at around the same level of global warming.</p>
<p>Stopping carbon emissions will <a href="https://www.carbonbrief.org/explainer-will-global-warming-stop-as-soon-as-net-zero-emissions-are-reached">cause</a> global warming to slow and, eventually, stop. Running these simulations for up to 1,000 years after carbon emissions stop will allow us to investigate and understand the effects of climate stabilisation in line with the Paris Agreement. </p>
<p>A few global modelling centres have started running simulations following similar frameworks, including Australia’s CSIRO. We invite other climate modelling centres to join us in our experiments, and help policymakers and societies better prepare for a warmer world.</p>
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Read more:
<a href="https://theconversation.com/the-seas-are-coming-for-us-in-kiribati-will-australia-rehome-us-172137">The seas are coming for us in Kiribati. Will Australia rehome us?</a>
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<img src="https://counter.theconversation.com/content/172482/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrew King receives funding from the Australian Research Council and the National Environmental Science Program. </span></em></p><p class="fine-print"><em><span>Andrea Dittus receives funding from the Natural Environment Research Council.</span></em></p><p class="fine-print"><em><span>Ed Hawkins receives funding from the UK Natural Environment Research Council (NERC).</span></em></p><p class="fine-print"><em><span>Josephine Brown receives funding from the Australian Research Council and the National Environmental Science Program.</span></em></p><p class="fine-print"><em><span>Kale Sniderman receives funding from the Australian Research Council</span></em></p><p class="fine-print"><em><span>Tilo Ziehn receives funding from the Australian Government under the National Environmental Science Program.</span></em></p>We need new experiments to model Earth’s climate if global warming is stabilised at 1.5°C. A new paper explains why.Andrew King, ARC DECRA fellow, The University of MelbourneAndrea Dittus, Research Scientist in Climate Variability, University of ReadingEd Hawkins, Professor of Climate Science, University of ReadingJosephine Brown, Senior Lecturer, The University of MelbourneKale Sniderman, Senior Research Fellow, The University of MelbourneTilo Ziehn, Principal Research Scientist, CSIROLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1703702021-10-28T19:15:32Z2021-10-28T19:15:32ZThe ‘97% climate consensus’ is over. Now it’s well above 99% (and the evidence is even stronger than that)<figure><img src="https://images.theconversation.com/files/428997/original/file-20211028-17-1z114vn.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C6233%2C3648&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Martin Meissner/AP</span></span></figcaption></figure><p>Despite the <a href="https://theconversation.com/99-999-certainty-humans-are-driving-global-warming-new-study-29911">overwhelming evidence</a>, it’s still common to see <a href="https://theconversation.com/australias-stumbling-last-minute-dash-for-climate-respectability-doesnt-negate-a-decade-of-abject-failure-169891">politicians</a>, media commentators or social media users cast doubt on the role of humans in driving climate change.</p>
<p>But this denialism is now almost nonexistent among climate scientists, as a <a href="https://iopscience.iop.org/article/10.1088/1748-9326/ac2966">study released this month</a> confirms. US researchers examined the peer-reviewed literature and found more than 99% of climate scientists now endorse the evidence for human-induced climate change. </p>
<p>That’s even higher than the 97% reported by an influential <a href="https://iopscience.iop.org/article/10.1088/1748-9326/8/2/024024/meta">2013 study</a>, which has become a widely cited statistic by both climate change deniers and those who accept the evidence. </p>
<p>Why has the needle evidently shifted even more firmly in favour of the evidence-based consensus? Or, to put it another way, what happened to the 3% of researchers who rejected the consensus of human caused climate change? Is this change purely because of the growing weight of evidence published over the past few years?</p>
<h2>Unpicking the polls</h2>
<p>We must first ask whether the two studies are directly comparable. The answer is yes. The <a href="https://iopscience.iop.org/article/10.1088/1748-9326/ac2966">latest study</a> has reexamined the literature published since 2012, and is based on the same methods as the <a href="https://theconversation.com/consensus-confirmed-over-90-of-climate-scientists-believe-were-causing-global-warming-57654">2013 study</a>, albeit with some important refinements.</p>
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Read more:
<a href="https://theconversation.com/consensus-confirmed-over-90-of-climate-scientists-believe-were-causing-global-warming-57654">Consensus confirmed: over 90% of climate scientists believe we're causing global warming</a>
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<p>Both studies searched the <a href="https://clarivate.com/webofsciencegroup/solutions/web-of-science/">Web of Science</a> database – an independent worldwide repository of scientific paper citations – using the keywords “global climate change” and “global warming”. However, the recent study added “climate change” to the other two keyword searches, because the <a href="https://iopscience.iop.org/article/10.1088/1748-9326/ac2966">authors found</a> that most climate-contrarian papers would not have been returned with only the two original terms.</p>
<p>The <a href="https://iopscience.iop.org/article/10.1088/1748-9326/8/2/024024/meta">2013 study</a> examined 11,944 climate research papers and found almost one-third of them expressed a position on the cause of global warming. Of these 4,014 papers, 97% endorsed the consensus position that humans are the cause, 1% were uncertain, and 2% explicitly rejected it.</p>
<p>A <a href="https://link.springer.com/article/10.1007/s00704-015-1597-5">2015 review</a> examined 38 climate-contrarian papers published over the preceding decade, and identified a range of methodological flaws and sources of bias.</p>
<p>One of the <a href="https://qz.com/1069298/the-3-of-scientific-papers-that-deny-climate-change-are-all-flawed/">reviewers commented</a> that “every single one of those analyses had an error – in their assumptions, methodology, or analysis – that, when corrected, brought their results into line with the scientific consensus”.</p>
<p>For example, many of the contrarian papers had “<a href="https://dictionary.cambridge.org/dictionary/english/cherry-pick">cherrypicked</a>” results that supported their conclusion, while ignoring important context and other data sources that contradicted it. Some of them simply ignored fundamental physics.</p>
<p>The 2015 reviewers also made the important point that “science is never settled and that both mainstream and contrarian papers must be subjected to sustained scrutiny”. This is the cornerstone of the <a href="https://www.britannica.com/science/scientific-method">scientific method</a>, and few if any climate scientists would disagree with this statement. </p>
<h2>Separating the human influence from the natural</h2>
<p>The recently published Intergovernmental Panel for Climate Change (IPCC) <a href="https://www.ipcc.ch/assessment-report/ar6/">Synthesis Report</a>, says “it is unequivocal that human influence has warmed the atmosphere, ocean and land”, and warns that the Paris Agreement goals of 1.5°C and 2°C above pre-industrial levels will be <a href="https://theconversation.com/if-all-2030-climate-targets-are-met-the-planet-will-heat-by-2-7-this-century-thats-not-ok-170458">exceeded during this century</a> without dramatic emissions reductions.</p>
<p>In reaching this conclusion, it is important to distinguish between changes caused by <a href="https://www.science.org.au/curious/earth-environment/enhanced-greenhouse-effect">human activities</a> altering the atmosphere’s chemistry, and <a href="https://www.pacificclimatefutures.net/en/help/climate-projections/understanding-climate-variability-and-change/">climate variability</a> caused by natural factors. </p>
<p>These natural variations include small changes in the <a href="https://climate.nasa.gov/blog/2910/what-is-the-suns-role-in-climate-change/">Sun’s energy output</a> due to sunspots and solar flares, infrequent <a href="https://www.usgs.gov/natural-hazards/volcano-hazards/volcanoes-can-affect-climate">volcanic eruptions</a>, and the effects of <a href="https://www.carbonbrief.org/interactive-much-el-nino-affect-global-temperature">El Niño</a> weather patterns in the Pacific Ocean. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/428996/original/file-20211028-17-1y4ntru.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Graphs of global temperatures" src="https://images.theconversation.com/files/428996/original/file-20211028-17-1y4ntru.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/428996/original/file-20211028-17-1y4ntru.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=314&fit=crop&dpr=1 600w, https://images.theconversation.com/files/428996/original/file-20211028-17-1y4ntru.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=314&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/428996/original/file-20211028-17-1y4ntru.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=314&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/428996/original/file-20211028-17-1y4ntru.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=394&fit=crop&dpr=1 754w, https://images.theconversation.com/files/428996/original/file-20211028-17-1y4ntru.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=394&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/428996/original/file-20211028-17-1y4ntru.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=394&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">History of global temperature change and causes of recent warming.</span>
<span class="attribution"><span class="source">IPCC</span></span>
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</figure>
<p>Excluding these natural variations, Earth’s surface temperature was generally stable from about 2,000 to 1,000 years ago. After that, the planet cooled by about 0.3°C over <a href="https://www.ipcc.ch/assessment-report/ar6/">several centuries</a>, before the advent of fossil fuel-based industrialisation in the 1800s.</p>
<p>One <a href="https://www.researchgate.net/publication/344709426_Prominent_role_of_volcanism_in_Common_Era_climate_variability_and_human_history">study</a> identified 12 major volcanic eruptions from 100 to 1200 CE, compared with 17 eruptions from 1200 to 1900 CE. Hence, heightened volcanic activity over roughly the past 800 years was associated with a general global cooling before the industrial revolution. </p>
<p>Current rates of global warming are <a href="https://www.ipcc.ch/assessment-report/ar6/">unprecedented</a> in more than 2,000 years and temperatures now exceed the warmest (multi-century) period in <a href="https://www.ipcc.ch/assessment-report/ar6/">more than 100,000 years</a>. Global average <a href="https://www.ipcc.ch/assessment-report/ar6/">surface temperature</a> for the decade from 2011-20 was about 1.1°C higher than in 1850-1900. Each of the past four decades has been warmer than any preceding decade since 1850, when reliable weather observations began.</p>
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Read more:
<a href="https://theconversation.com/99-999-certainty-humans-are-driving-global-warming-new-study-29911">99.999% certainty humans are driving global warming: new study</a>
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<p>Researchers can separate human and natural factors in the modern global temperature record. This involves a process called <a href="https://www.climate.gov/maps-data/climate-data-primer/predicting-climate/climate-models">hindcasting</a>, in which a climate model is run backwards in time to simulate human and natural factors, and then compared with the observed data to see which combination of factors most accurately recreates the real world. </p>
<p>If human factors are removed from the data set and only volcanic and solar factors are included, then global average surface temperatures since 1950 should have remained similar to those over the preceding 100 years. But of course they haven’t.</p>
<p>The evidence, and the scientific consensus on it, are both clearer than ever.</p><img src="https://counter.theconversation.com/content/170370/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Steve Turton has previously received funding from the Australian Government. Steve is the independent chair of the Wet Tropics Healthy Waterways Partnership, an initiative of the Reef 2050 Long Term Sustainability Plan.</span></em></p>One of the most famous stats in the climate debate is the 97% of scientists who endorse the consensus on human-induced global heating. Ahead of the Glasgow summit, that figure has climbed even higher.Steve Turton, Adjunct Professor of Environmental Geography, CQUniversity AustraliaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1701812021-10-26T14:33:32Z2021-10-26T14:33:32ZDune: we simulated the desert planet of Arrakis to see if humans could survive there<p>Dune, the epic series of sci-fi books by Frank Herbert, now turned into a movie of the same name, is set in the far future on the desert planet of Arrakis. Herbert outlined a richly-detailed world that, at first glance, seems so real we could imagine ourselves within it.</p>
<p>However, if such a world did exist, what would it actually be like? </p>
<p>We are scientists with specific expertise in climate modelling, so we simulated the climate of Arrakis to find out. We wanted to know if the physics and environment of such a world would stack up against a real climate model. </p>
<p>Here’s a visualisation of our climate model of Arrakis:</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/427871/original/file-20211021-15766-1q37jmx.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/427871/original/file-20211021-15766-1q37jmx.gif?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=429&fit=crop&dpr=1 600w, https://images.theconversation.com/files/427871/original/file-20211021-15766-1q37jmx.gif?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=429&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/427871/original/file-20211021-15766-1q37jmx.gif?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=429&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/427871/original/file-20211021-15766-1q37jmx.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=539&fit=crop&dpr=1 754w, https://images.theconversation.com/files/427871/original/file-20211021-15766-1q37jmx.gif?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=539&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/427871/original/file-20211021-15766-1q37jmx.gif?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=539&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p>You can zoom in on particular features and highlight things like temperature or wind speed at our website <a href="https://climatearchive.org/dune">Climate Archive</a>.</p>
<p>When we were done, we were very pleased to discover that Herbert had envisioned an environment that for the most part meets expectations. We might need to occasionally suspend disbelief, but much of Arrakis itself would indeed be habitable, albeit inhospitable.</p>
<hr>
<iframe id="noa-web-audio-player" style="border: none" src="https://embed-player.newsoveraudio.com/v4?key=x84olp&id=https://theconversation.com/dune-we-simulated-the-desert-planet-of-arrakis-to-see-if-humans-could-survive-there-170181&bgColor=F5F5F5&color=D8352A&playColor=D8352A" width="100%" height="110px"></iframe>
<p><em>You can listen to more articles from The Conversation, narrated by Noa, <a href="https://theconversation.com/uk/topics/audio-narrated-99682">here</a>.</em></p>
<hr>
<h2>How do you build a fantasy world like Arrakis?</h2>
<p>We started with a climate model commonly used to predict weather and climate here on Earth. To use these sorts of models you have to decide on the physical laws (well-known in the case of planet Earth) and then input data on everything from the shape of mountains to the strength of the sun or the makeup of the atmosphere. The model can then simulate the climate and tell you roughly what the weather might be like.</p>
<p>We decided to keep the same fundamental physical laws that govern weather and climate here on Earth. If our model presented something completely strange and exotic, this could suggest those laws were different on Arrakis, or Frank Herbert’s fantastical vision of Arrakis was just that, fantasy.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/429112/original/file-20211028-20-frajzm.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/429112/original/file-20211028-20-frajzm.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/429112/original/file-20211028-20-frajzm.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=209&fit=crop&dpr=1 600w, https://images.theconversation.com/files/429112/original/file-20211028-20-frajzm.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=209&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/429112/original/file-20211028-20-frajzm.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=209&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/429112/original/file-20211028-20-frajzm.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=263&fit=crop&dpr=1 754w, https://images.theconversation.com/files/429112/original/file-20211028-20-frajzm.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=263&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/429112/original/file-20211028-20-frajzm.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=263&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Height map (in metres) of Arrakis.</span>
<span class="attribution"><span class="source">Farnsworth et al</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>We then needed to tell the climate model certain things about Arrakis, based on the detailed information found in the main novels and the accompanying <a href="https://www.goodreads.com/book/show/870294.The_Dune_Encyclopedia">Dune Encyclopedia</a>. These included the planet’s topography and its orbit, which was was essentially circular, akin to the Earth today. The shape of an orbit can really impact the climate: see the long and irregular winters in <a href="https://theconversation.com/weathermen-of-westeros-does-the-climate-in-game-of-thrones-make-sense-43076">Game of Thrones</a>. </p>
<p>Finally, we told the model what the atmosphere was made of. For the most part it is quite similar to that of the Earth today, although with less carbon dioxide (350 parts per million as opposed to our 417 ppm). The biggest difference is the ozone concentration. On Earth, there is very little ozone in the lower atmosphere, only around 0.000001%. On Arrakis it is 0.5%. Ozone is important as it is around <a href="http://www.atmo.arizona.edu/students/courselinks/spring04/atmo451b/pdf/RadiationBudget.pdf">65 times more effective</a> at warming the atmosphere than CO₂ over a 20-year period.</p>
<p>Having fed in all the necessary data, we then sat back and waited. Complex models like this take time to run, in this case more than three weeks. We needed a huge supercomputer to be able to crunch the hundreds of thousands of calculations required to simulate Arrakis. However, what we found was worth the wait.</p>
<h2>Arrakis’s climate is basically plausible</h2>
<p>The books and film describe a planet with unforgiving sun and desolate wastelands of sand and rock. However, as you move closer to the polar regions towards the cities of Arrakeen and Carthag, the climate in the book begins to change into something that might be inferred as more hospitable. </p>
<p>Yet our model tells a different story. In our model of Arrakis, the warmest months in the tropics hit around 45°C, whereas in the coldest months they do not drop below 15°C. Similar to that of Earth. The most extreme temperatures would actually occur in the mid-latitudes and polar regions. Here summer can be as hot as 70°C on the sand (also suggested in the book). Winters are just as extreme, as low as -40°C in the mid-latitudes and down to -75°C in the poles. </p>
<p>This is counter intuitive as the equatorial region receives more energy from the sun. However, in the model the polar regions of Arrakis have significantly more atmospheric moisture and high cloud cover which acts to warm the climate since water vapour is a greenhouse gas. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/428025/original/file-20211022-22-1qsep5l.gif?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="gif of temperatures" src="https://images.theconversation.com/files/428025/original/file-20211022-22-1qsep5l.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/428025/original/file-20211022-22-1qsep5l.gif?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=425&fit=crop&dpr=1 600w, https://images.theconversation.com/files/428025/original/file-20211022-22-1qsep5l.gif?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=425&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/428025/original/file-20211022-22-1qsep5l.gif?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=425&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/428025/original/file-20211022-22-1qsep5l.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=534&fit=crop&dpr=1 754w, https://images.theconversation.com/files/428025/original/file-20211022-22-1qsep5l.gif?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=534&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/428025/original/file-20211022-22-1qsep5l.gif?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=534&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Monthly temperatures on Arrakis, according to the model. Both poles have very cold winters and very hot summers.</span>
<span class="attribution"><span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>The book says that there is no rain on Arrakis. However, our model does suggest that very small amounts of rainfall would occur, confined to just the higher latitudes in the summer and autumn, and only on mountains and plateaus. There would be some clouds in the tropics as well as polar latitudes, varying from season to season.</p>
<p>The book also mentions that polar ice caps exist, at least in the northern hemisphere, and have for a long time. But this is where the books perhaps differ the most from our model, which suggests summer temperatures would melt any polar ice, and there would be no snowfall to replenish the ice caps in winter.</p>
<h2>Hot but habitable</h2>
<p>Could humans survive on such a desert planet? First, we must make an assumption that the human-like people in the book and film share similar thermal tolerances to humans today. If that’s the case then, contrary to the book and film, it seems the tropics would be the most habitable area. As there is so little humidity there, survivable <a href="https://theconversation.com/heatwave-think-its-hot-in-europe-the-human-body-is-already-close-to-thermal-limits-elsewhere-121003">wet-bulb temperatures</a> – a measure of “habitability” that combines temperature and humidity – are never exceeded. </p>
<p>The mid-latitudes, where most people on Arrakis live, are actually the most dangerous in terms of heat. In the lowlands, monthly average temperatures are often above 50-60°C, with maximum daily temperatures even higher. Such temperatures are deadly for humans.</p>
<p>We do know that all humanoid life on Arrakis outside of habitable places must wear “stillsuits”, designed to keep the wearer cool and reclaim body moisture from sweating, urination and breathing to provide drinkable water. This is important as stated in the book that there is no rainfall on Arrakis, no standing bodies of open water and little atmospheric moisture that can be reclaimed.</p>
<p>The planet also gets very cold outside of the tropics, with winter temperatures that would also be uninhabitable without technology. Cities like Arrakeen and Carthag would suffer from both heat and cold stress, like a more extreme version of parts of Siberia on Earth which can have both uncomfortably hot summers and brutally cold winters.</p>
<p>It’s important to remember that Herbert wrote the first Dune novel way back in 1965. This was two years before recent Nobel-winner Syukuro Manabe published his seminal <a href="https://theconversation.com/the-most-influential-climate-science-paper-of-all-time-169382">first climate model</a>, and Herbert did not have the advantage of modern supercomputers, or indeed any computer. Given that, the world he created looks remarkably consistent six decades on.</p>
<hr>
<p><em>The authors modified a well-used climate model for exoplanet research and applied it to the planet in Dune. The work was carried out in their spare time and is intended as an appropriate outreach piece to demonstrate how climate scientists use mathematical models to better understand our world and exoplanets. It will feed into future academic outputs on desert worlds and exoplanets.</em></p><img src="https://counter.theconversation.com/content/170181/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alex Farnsworth receives funding from UK Research and Innovation. He is affiliated with the Institute of Tibetan Plateau Research (ITP), Chinese Academy of Sciences.</span></em></p><p class="fine-print"><em><span>Sebastian Steinig receives funding from the Natural Environment Research Council and has been supported by the Jean Golding Institute for data science and data-intensive research at the University of Bristol. </span></em></p><p class="fine-print"><em><span>Michael Farnsworth does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Is Dune scientifically plausible? We ran a climate model to find out.Alex Farnsworth, Senior Research Associate in Meteorology, University of BristolMichael Farnsworth, Research Lead Future Electrical Machines Manufacturing Hub, University of SheffieldSebastian Steinig, Research Associate in Paleoclimate Modelling, University of BristolLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1696512021-10-15T09:02:34Z2021-10-15T09:02:34ZWidespread collapse of West Antarctica’s ice sheet is avoidable if we keep global warming below 2°C<figure><img src="https://images.theconversation.com/files/426150/original/file-20211013-21-1bpn74z.jpg?ixlib=rb-1.1.0&rect=43%2C149%2C5825%2C3766&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>Rising seas are already making storm damage <a href="https://www.nature.com/articles/s41467-021-22838-1">more costly</a>, adding to the impact on about 700 million people who live in low-lying coastal areas at risk of <a href="https://www.ipcc.ch/srocc/chapter/chapter-4-sea-level-rise-and-implications-for-low-lying-islands-coasts-and-communities/">flooding</a>. </p>
<p>Scientists expect sea-level rise will exacerbate the damage from storm surges and coastal floods during the coming <a href="https://www.nature.com/articles/s41598-020-67736-6">decades</a>. But predicting just how much and how fast the seas will rise this century is difficult, mainly because of uncertainties about how Antarctica’s ice sheet will behave. </p>
<p>The recent Intergovernmental Panel on Climate Change (<a href="https://www.ipcc.ch/">IPCC</a>) <a href="https://www.ipcc.ch/assessment-report/ar6/">projections</a> of Antarctica’s contribution to sea-level rise show considerable overlap between low and high-emissions <a href="https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_Chapter_09.pdf">scenarios</a>. </p>
<p>But in our new <a href="https://doi.org/10.1038/s43247-021-00289-2">research</a>, we show the widespread collapse of the West Antarctic Ice Sheet is avoidable if we can keep global warming below the Paris target of 2°C.</p>
<p>In West Antarctica, the interior of the ice sheet sits atop bedrock that lies well below sea level. As the Southern Ocean warms, scientists are concerned the ice sheet will continue to retreat, potentially raising sea level by <a href="https://www.nature.com/articles/ngeo1194">several meters</a>. </p>
<p>When and how quickly this process could happen depends on a number of factors that are still uncertain. </p>
<p>Our research better quantifies these uncertainties and shows the full impact of different emissions trajectories on Antarctica may not become clear until after 2100. But the consequences of decisions we make this decade will be felt for centuries. </p>
<figure class="align-center ">
<img alt="People standing on a ridge in Antarctica." src="https://images.theconversation.com/files/426308/original/file-20211013-19-1panpis.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/426308/original/file-20211013-19-1panpis.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=242&fit=crop&dpr=1 600w, https://images.theconversation.com/files/426308/original/file-20211013-19-1panpis.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=242&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/426308/original/file-20211013-19-1panpis.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=242&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/426308/original/file-20211013-19-1panpis.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=304&fit=crop&dpr=1 754w, https://images.theconversation.com/files/426308/original/file-20211013-19-1panpis.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=304&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/426308/original/file-20211013-19-1panpis.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=304&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">New modelling shows if warming stays below 2°C, West Antarctica’s ice sheet remains intact.</span>
<span class="attribution"><span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>A new approach to projecting change in Antarctica</h2>
<p>Scientists have used numerical ice-sheet models for decades to understand how ice sheets evolve under different climate states. These models are based on mathematical equations that represent how ice sheets flow.</p>
<p>But despite advances in mapping the bed topography <a href="https://www.nature.com/articles/s41561-019-0510-8">beneath the ice</a>, significant uncertainty remains in terms of the internal ice structure and conditions of the bedrock and sediment below. Both affect ice flow. </p>
<p>This makes prediction difficult, because the models have to rely on a series of assumptions, which affect how sensitive a modelled ice sheet is to a changing climate. Given the number and complexity of the equations, running ice-sheet models can be time consuming, and it may be impossible to fully account for all of the uncertainty. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/scientists-still-dont-know-how-far-melting-in-antarctica-will-go-or-the-sea-level-rise-it-will-unleash-166677">Scientists still don’t know how far melting in Antarctica will go – or the sea level rise it will unleash</a>
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<p>To overcome this limitation, researchers around the world are now frequently using statistical “emulators”. These mathematical models can be trained using results from more complex ice-sheet models and then used to run thousands of alternative scenarios. </p>
<p>Using hundreds of ice-sheet model simulations as training data, we developed such an emulator to project Antarctica’s sea-level contribution under a wide range of emissions scenarios. We then ran tens of thousands of statistical emulations to better quantify the uncertainties in the ice sheet’s response to warming.</p>
<h2>Low emissions prevent ice shelf thinning</h2>
<p>To ensure our projections are realistic, we discounted any simulation that did not fit with satellite observations of Antarctic ice loss over the last <a href="https://www.pnas.org/content/116/4/1095.short">four decades</a>. </p>
<p>We considered a low-emissions scenario, in which global carbon emissions were reduced quickly over the next few decades, and a high-emissions scenario, in which emissions kept increasing to the end of the century. Under both scenarios, we observed continued ice loss in areas already losing ice mass, such as the <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2013GL059069">Amundsen Sea region of West Antarctica</a>.</p>
<figure class="align-center ">
<img alt="These maps of Antarctica show the projected change in ice thickness between the present and the year 2300, for a low-emissions scenario (left) and a high-emissions scenario (right), with red indicating ice loss and blue showing ice gain." src="https://images.theconversation.com/files/426306/original/file-20211013-17-1niuf2g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/426306/original/file-20211013-17-1niuf2g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=430&fit=crop&dpr=1 600w, https://images.theconversation.com/files/426306/original/file-20211013-17-1niuf2g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=430&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/426306/original/file-20211013-17-1niuf2g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=430&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/426306/original/file-20211013-17-1niuf2g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=540&fit=crop&dpr=1 754w, https://images.theconversation.com/files/426306/original/file-20211013-17-1niuf2g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=540&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/426306/original/file-20211013-17-1niuf2g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=540&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">These maps of Antarctica show the projected change in ice thickness between the present and the year 2300, for a low-emissions scenario (left) and a high-emissions scenario (right), with red indicating ice loss and blue showing ice gain.</span>
<span class="attribution"><span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>For the ice sheet as a whole, we found no statistically significant difference between the ranges of plausible contributions to sea-level rise in the two emissions scenarios until the year 2116. However, the rate of sea-level rise towards the end of this century under high emissions was double that of the low-emissions scenario. </p>
<p>By 2300, under high emissions, the Antarctic ice sheet contributed more than 1.5m more to global sea level than in the low-emissions scenario. This is because the West Antarctic Ice Sheet collapses.</p>
<p>The earliest warning sign of a future with a multi-metre Antarctic contribution to sea-level rise is widespread thinning of Antarctica’s two largest floating ice shelves, the Ross and Ronne-Filchner. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/antarcticas-ice-shelves-are-trembling-as-global-temperatures-rise-what-happens-next-is-up-to-us-158540">Antarctica's ice shelves are trembling as global temperatures rise – what happens next is up to us</a>
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<hr>
<p>These massive ice shelves hold back land-based ice, but as they thin and break off, this resistance weakens. The land-based ice flows more easily into the ocean, raising sea level. </p>
<p>In the high-emissions scenario, this widespread ice-shelf thinning happens within the next few decades. But importantly, these ice shelves show no thinning in a low-emissions scenario — most of the West Antarctic Ice Sheet remains intact.</p>
<h2>Planning our future</h2>
<p>The goal of the Paris Agreement is to keep warming well below 2°C. But current global government pledges commit us to <a href="https://climateactiontracker.org/publications/global-update-climate-summit-momentum/">2.9°C by 2100</a>. Based on our emulator projections, we believe these pledges would lead to a 50% higher (70cm) Antarctic contribution to sea-level rise by the year 2300 than if warming remains at or under 2°C.</p>
<p>But even if we meet the Paris target, we are already committed to sea-level rise from the Antarctic ice sheet, as well as from Greenland and mountain glaciers around the world for <a href="https://wires.onlinelibrary.wiley.com/doi/10.1002/wcc.634">centuries or millennia to come</a>. </p>
<p>Continued warming will also raise sea levels because warmer ocean water expands and the amount of water stored on land (in soil, aquifers, wetlands, lakes, and reservoirs) changes. </p>
<p>To avoid the worst impacts on coastal communities around the world, planners and policymakers will need to develop meaningful adaptation strategies and mitigation options for the continued threat of sea-level rise.</p><img src="https://counter.theconversation.com/content/169651/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dan Lowry receives funding from the Ministry for Business, Innovation, and Employment. He was a Contributing Author on the IPCC Sixth Assessment Report (AR6).</span></em></p><p class="fine-print"><em><span>Mario Krapp receives funding from the Ministry for Business, Innovation, and Employment.</span></em></p><p class="fine-print"><em><span>Nick Golledge receives funding from the Royal Society Te Apārangi and from the Ministry for Business, Innovation, and Employment. He was a Lead Author on the IPCC Sixth Assessment Report (AR6).</span></em></p>A new modelling approach improves projections of Antarctica’s future ice loss. It shows a low-emissions scenario would avoid the collapse of West Antarctica’s ice sheet and limit sea-level rise.Dan Lowry, Ice Sheet & Climate Modeller, GNS ScienceMario Krapp, Environmental Data Scientist, GNS ScienceNick Golledge, Professor of Glaciology, Te Herenga Waka — Victoria University of WellingtonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1693822021-10-07T13:08:53Z2021-10-07T13:08:53ZThe most influential climate science paper of all time<p>After the second world war, many of Japan’s smartest scientists found jobs in North American laboratories. Syukuro (Suki) Manabe, a 27-year-old physicist, was part of this brain drain. He was working on weather forecasting but left Japan in 1958 to join a new research project by the US Weather Service to develop a numerical model that could be used to <a href="https://history.aip.org/climate/index.htm">study the climate</a>.</p>
<p>Working alongside Joseph Smagorinsky, the <a href="https://www.gfdl.noaa.gov/">Geophysical Fluid Dynamics Laboratory’s</a> visionary first director, Manabe led a team of computer programmers to add missing physics to the lab’s weather model. Even the best computers in the world at the time were far less powerful than today’s mobile phones. So to get the model to work, Manabe needed to make the physics as simple as possible. This meant making a range of coding approximations to quantify how the air exchanged heat and water vapour with the land, ocean and ice.</p>
<p>This climate model development – the first of its kind – was an ambitious 20-year project that ultimately earned Manabe a share of the <a href="https://www.nobelprize.org/prizes/physics/2021/press-release/">2021 Nobel prize in physics</a>. The key paper came mid-way through this period: <a href="https://journals.ametsoc.org/view/journals/atsc/24/3/1520-0469_1967_024_0241_teotaw_2_0_co_2.xml">Manabe and Wetherald (1967)</a>. </p>
<p>Manabe is typically modest about intentions behind the work and from reading its title, “Thermal Equilibrium of the Atmosphere with a Given Distribution of Relative Humidity”, you might be forgiven for thinking it could be a bit dull. Yet the Nobel committee, myself and the hundreds of colleagues around the world that voted it the <a href="https://www.carbonbrief.org/the-most-influential-climate-change-papers-of-all-time">most influential climate science paper of all time</a>, would beg to differ.</p>
<p>In trying to simplify the code, Manabe and his colleague Richard Wetherald wanted to know the minimum number of discrete levels to use in his model atmosphere. They also wanted to know which greenhouse gases it was necessary to include in the model to adequately represent the way temperatures vary with altitude, as these gases absorb heat emitted from the Earth’s surface, but at different levels. Their three-dimensional climate model was too computer-intensive to run these model tests, so they had to build a simpler one-dimensional model. They wanted to simulate how radiation and clouds interact to redistribute heat and water vapour through the atmosphere.</p>
<p>The bulk of the paper concerns itself with building the simple model and doing these tests. But they also do two other experiments in the paper to quantify how greenhouse gas might alter climate. And this is where the breakthrough occurred: they found they had built the perfect model to accurately estimate how human activities could alter the Earth’s surface temperature.</p>
<p>Their first such climate-change experiment wasn’t to look at the role of carbon dioxide, but was to look at the effects of water vapour injected high into the stratosphere from a potential fleet of supersonic jets, as this and a possible nuclear winter were the immediate concerns of the time. However, their Table 5 goes down in history as the first robust estimate of how much the world would warm if carbon dioxide concentrations doubled. Manabe and Wetherald estimated 2.36°C of warming, not far off <a href="https://www.ipcc.ch/report/ar6/wg1/">today’s best estimate of 3°C</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/425163/original/file-20211007-17-13nl4qx.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Graph showing warming at different altitudes and levels of CO2" src="https://images.theconversation.com/files/425163/original/file-20211007-17-13nl4qx.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/425163/original/file-20211007-17-13nl4qx.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=474&fit=crop&dpr=1 600w, https://images.theconversation.com/files/425163/original/file-20211007-17-13nl4qx.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=474&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/425163/original/file-20211007-17-13nl4qx.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=474&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/425163/original/file-20211007-17-13nl4qx.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=596&fit=crop&dpr=1 754w, https://images.theconversation.com/files/425163/original/file-20211007-17-13nl4qx.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=596&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/425163/original/file-20211007-17-13nl4qx.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=596&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Manabe modelled the links between temperature, altitude and CO2 levels.</span>
<span class="attribution"><span class="source">Johan Jarnestad / Royal Swedish Academy of Sciences / Manabe & Wetherald (1967), Journal of the Atmospheric Sciences</span></span>
</figcaption>
</figure>
<p>Earlier attempts to estimate the warming from carbon dioxide increases had floundered, as scientists struggled to work out how water vapour, the most important greenhouse gas in the atmosphere, would respond as the Earth warmed. Manabe and Wetherald’s simple model could accurately redistribute water vapour in a way that real deep clouds do, with water vapour broadly increasing in concentration up to a certain level of humidity. This increase was found to amplify the warming from carbon dioxide by around 75%. This water vapour feedback estimate has also stood the test of time.</p>
<p>Manabe, working with various colleagues, went on to write many more <a href="https://journals.ametsoc.org/view/journals/atsc/32/1/1520-0469_1975_032_0003_teodtc_2_0_co_2.xml">seminal climate modelling papers</a>. He set the foundation for today’s global climate modelling efforts. The physics was beguilingly simple so his models could run on these early computers. Yet, by being simple, the results could be understood and tested. His application of these simple models to the pressing problems of today was insightful.</p>
<p>After graduating with a degree in physics over 30 years ago, I chose a <a href="https://environment.leeds.ac.uk/see/staff/1267/professor-piers-forster">career in atmospheric science</a> over particle physics. I always worried about how my applied physics was viewed by mainstream physics colleagues. With a Nobel prize in physics under our discipline’s belt, it gives me and climate modelling colleagues the credibility and recognition we have yearned for: climate science is real science.</p><img src="https://counter.theconversation.com/content/169382/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Piers Forster receives funding from UK Research Councils and the EU Horizon 2020 programme. He is Trustee of the United Bank of Carbon Forest Charity.</span></em></p>A 1967 study by Nobel-winner Syukuro Manabe changed climate science foreverPiers Forster, Professor of Physical Climate Change; Director of the Priestley International Centre for Climate, University of LeedsLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1693002021-10-05T17:26:22Z2021-10-05T17:26:22ZNobel prize: why climate modellers deserved the physics award – they’ve been proved right again and again<figure><img src="https://images.theconversation.com/files/424813/original/file-20211005-17-efbtrt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">metamorworks / shutterstock</span></span></figcaption></figure><p>This year’s Nobel prize in physics has been split between Syukuro Manabe, Klaus Hasselmann and Giorgio Parisi. While Parisi is a <a href="https://iopscience.iop.org/article/10.1088/0305-4470/13/4/009/meta">theoretical physicist</a>, the other two are climate modellers whose work laid the foundations of our understanding of how carbon dioxide would shape the climate. </p>
<p>This award couldn’t be more timely, as the most recent <a href="https://theconversation.com/this-is-the-most-sobering-report-card-yet-on-climate-change-and-earths-future-heres-what-you-need-to-know-165395">IPCC report</a>, based on state-of-the-art climate models, states unequivocally that humans are already influencing many weather and climate extremes in every region across the globe. </p>
<p>A climate model is a computer program designed to simulate Earth’s climate in order to understand and predict its behaviour. Climate models are largely based on a set of mathematical equations that describe the physical laws which govern the behaviour of the atmosphere and ocean, and their interactions with other parts of Earth’s climate system such as land surface or ice sheets. (Think of how melting ice sheets mean less of the sun’s energy is reflected back into space, thereby causing more warming and further melting and so on.)</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/424817/original/file-20211005-27-10elnnu.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Graph showing how CO2 levels affect temperature at different altitudes" src="https://images.theconversation.com/files/424817/original/file-20211005-27-10elnnu.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/424817/original/file-20211005-27-10elnnu.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=553&fit=crop&dpr=1 600w, https://images.theconversation.com/files/424817/original/file-20211005-27-10elnnu.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=553&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/424817/original/file-20211005-27-10elnnu.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=553&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/424817/original/file-20211005-27-10elnnu.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=694&fit=crop&dpr=1 754w, https://images.theconversation.com/files/424817/original/file-20211005-27-10elnnu.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=694&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/424817/original/file-20211005-27-10elnnu.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=694&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Manabe and Wetherald accurately predicted how much the world would warm when the amount of carbon dioxide in the atmosphere increased.</span>
<span class="attribution"><span class="source">Johan Jarnestad / Royal Swedish Academy of Sciences / Manabe & Wetherald (1967), Journal of the Atmospheric Sciences</span></span>
</figcaption>
</figure>
<p>In the 1960s, Manabe did some of the earliest climate modelling experiments to understand how carbon dioxide might cause a greenhouse effect. In an important 1967 paper, he along with his colleague Richard Wetherald showed how rising carbon dioxide levels would lead to a <a href="https://journals.ametsoc.org/view/journals/atsc/24/3/1520-0469_1967_024_0241_teotaw_2_0_co_2.xml?tab_body=pd">rise in the temperatures at Earth’s surface</a>. </p>
<p>The authors treated Earth’s atmosphere as a simple one-dimensional column, and showed that if carbon dioxide levels doubled, global temperatures would rise by about 2.3°C – a finding that is remarkably similar to the answers given five decades later by high-powered computer models used in IPCC reports. No wonder one survey of scientists found it was <a href="https://www.carbonbrief.org/the-most-influential-climate-change-papers-of-all-time">the most influential climate change paper of all time</a></p>
<p>Research by Hasselmann in the 1980s showed how, despite the short-term variability of weather, climate models could be used to <a href="https://pure.mpg.de/rest/items/item_3030122/component/file_3030123/content%5D">predict trends decades into the future</a>. Back in the 80s we knew little about these longer term trends but now, thanks to Hasselmann’s and Manabe’s work, we can for instance state that the 2030s are likely going to involve more heat waves, floods and other climate extremes. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/424816/original/file-20211005-15-19gpams.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Graph showing global warming caused by humans, by natural processes like volcanic eruptions, and combined effects." src="https://images.theconversation.com/files/424816/original/file-20211005-15-19gpams.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/424816/original/file-20211005-15-19gpams.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=446&fit=crop&dpr=1 600w, https://images.theconversation.com/files/424816/original/file-20211005-15-19gpams.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=446&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/424816/original/file-20211005-15-19gpams.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=446&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/424816/original/file-20211005-15-19gpams.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=561&fit=crop&dpr=1 754w, https://images.theconversation.com/files/424816/original/file-20211005-15-19gpams.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=561&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/424816/original/file-20211005-15-19gpams.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=561&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Klaus Hasselmann’s work helped identify what proportion of global warming was and wasn’t caused by human activities.</span>
<span class="attribution"><span class="source">Johan Jarnestad / Royal Swedish Academy of Sciences</span></span>
</figcaption>
</figure>
<p>Being a climate modeller myself, I know their work has contributed to huge benefits for humankind, as it provides the solid physical foundation for our knowledge of Earth’s climate. We can no longer say that we did not know – the climate models are unequivocal and have been proven right time and again. </p>
<p>Is Earth heating up (yes)? Is the cause the increased amounts of greenhouse gases in the atmosphere (yes)? Can this be explained solely by natural factors (no)? Are humanity’s emissions the reason for the increasing temperature (yes)? All these questions and more have been answered by these state-of-the-art climate models. </p>
<p>These models have helped immensely as scientists seek to understand climate change and anticipate its risks. They provided the basis for predicting impacts, guiding adaptation decisions and setting mitigation targets. Latest developments involve ever more details of our earth system, providing precise information to enable robust decision-making in the face of rapidly amplifying climate change.</p><img src="https://counter.theconversation.com/content/169300/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Pushp Raj Tiwari does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Syukuro Manabe and Klaus Hasselmann have won the Nobel prize in physics for their climate modelling research.Pushp Raj Tiwari, University ECR Fellow, Centre for Atmospheric and Climate Physics Research, University of HertfordshireLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1658182021-08-17T19:57:30Z2021-08-17T19:57:30ZHow machine learning is helping us fine-tune climate models to reach unprecedented detail<figure><img src="https://images.theconversation.com/files/416467/original/file-20210817-52421-1a6w83e.jpeg?ixlib=rb-1.1.0&rect=6%2C19%2C4336%2C2871&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>From movie suggestions to self-driving vehicles, machine learning has revolutionised modern life. Experts are now using it to help solve one of humanity’s biggest problems: climate change.</p>
<p>With machine learning, we can use our abundance of historical climate data and observations to improve predictions of Earth’s future climate. And these predictions will have a major role in lessening our climate impact in the years ahead.</p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/satellites-reveal-ocean-currents-are-getting-stronger-with-potentially-significant-implications-for-climate-change-159461">Satellites reveal ocean currents are getting stronger, with potentially significant implications for climate change</a>
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<h2>What is machine learning?</h2>
<p>Machine learning is a branch of artificial intelligence. While it has become something of a buzzword, it is essentially a process of extracting patterns from data.</p>
<p>Machine learning algorithms use available data sets to develop a model. This model can then make predictions based on new data that were not part of the original data set.</p>
<p>Going back to our climate problem, there are two main approaches by which machine learning can help us further our understanding of climate: observations and modelling. </p>
<p>In recent years, the amount of available data from observation and climate models has grown exponentially. It’s impossible for humans to go through it all. Fortunately, machines can do that for us.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/416472/original/file-20210817-25-1dshxrm.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/416472/original/file-20210817-25-1dshxrm.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=431&fit=crop&dpr=1 600w, https://images.theconversation.com/files/416472/original/file-20210817-25-1dshxrm.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=431&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/416472/original/file-20210817-25-1dshxrm.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=431&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/416472/original/file-20210817-25-1dshxrm.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=542&fit=crop&dpr=1 754w, https://images.theconversation.com/files/416472/original/file-20210817-25-1dshxrm.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=542&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/416472/original/file-20210817-25-1dshxrm.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=542&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">AI and computers can greatly aid efforts to create accurate climate models for the future.</span>
<span class="attribution"><span class="source">Josué Martínez-Moreno</span></span>
</figcaption>
</figure>
<h2>Observations from space</h2>
<p>Satellites are continuously monitoring the ocean’s surface, giving scientists useful insight into how ocean flows are changing. </p>
<p>NASA’s <a href="https://swot.jpl.nasa.gov">Surface Water and Ocean Topography (SWOT)</a> satellite mission — scheduled to launch late next year — aims to observe the ocean surface in unprecedented detail compared with current satellites. </p>
<p>But a satellite can’t observe the entire ocean at once. It can only see the portion of ocean beneath it. And the SWOT satellite will need 21 days to go over every point around the globe. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/416225/original/file-20210816-13-1pkev7i.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/416225/original/file-20210816-13-1pkev7i.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=592&fit=crop&dpr=1 600w, https://images.theconversation.com/files/416225/original/file-20210816-13-1pkev7i.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=592&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/416225/original/file-20210816-13-1pkev7i.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=592&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/416225/original/file-20210816-13-1pkev7i.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=745&fit=crop&dpr=1 754w, https://images.theconversation.com/files/416225/original/file-20210816-13-1pkev7i.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=745&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/416225/original/file-20210816-13-1pkev7i.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=745&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">This diagram shows the area covered by the SWOT satellite after three days in orbit. Although SWOT allows high-accuracy measurements, neighbouring areas in the ocean are not sampled as frequently.</span>
<span class="attribution"><span class="source">C. Ubelmann/CLS</span></span>
</figcaption>
</figure>
<p>Is there a way to fill in the missing data, so we can have a complete global picture of the ocean’s surface at any given moment?</p>
<p>This is where machine learning comes in. Machine learning algorithms can use data retrieved by the SWOT satellite to predict the missing data between each SWOT revolution. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/416226/original/file-20210816-15-ff94a5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/416226/original/file-20210816-15-ff94a5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/416226/original/file-20210816-15-ff94a5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/416226/original/file-20210816-15-ff94a5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/416226/original/file-20210816-15-ff94a5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/416226/original/file-20210816-15-ff94a5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/416226/original/file-20210816-15-ff94a5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/416226/original/file-20210816-15-ff94a5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">An artist’s impression of the SWOT satellite.</span>
<span class="attribution"><span class="source">NASA/CERN</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>Obstacles in climate modelling</h2>
<p>Observations inform us of the present. However, to predict future climate we must rely on comprehensive climate models. </p>
<p>The latest <a href="https://theconversation.com/mondays-ipcc-report-is-a-really-big-deal-for-climate-change-so-what-is-it-and-why-should-we-trust-it-165614">IPCC climate report</a> was informed by climate projections from various research groups across the world. These researchers ran a multitude of climate models representing different emissions scenarios that yielded projections hundreds of years into the future.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/climate-change-has-already-hit-australia-unless-we-act-now-a-hotter-drier-and-more-dangerous-future-awaits-ipcc-warns-165396">Climate change has already hit Australia. Unless we act now, a hotter, drier and more dangerous future awaits, IPCC warns</a>
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<p>To model the climate, computers overlay a computational grid on the oceans, atmosphere and land. Then, by starting with the climate of today, they can solve the equations of fluid and heat motion within each box of this grid to model how the climate will evolve in the future.</p>
<p>The size of each box in the grid is what we call the “resolution” of the model. The smaller the box’s size is, the finer the flow details the model can capture.</p>
<p>But running climate models that project forward hundreds of years brings even the most powerful supercomputers to their knees. Thus, we’re currently forced to run these models at a coarse resolution. In fact, it’s sometimes so coarse that the flow looks nothing like real life.</p>
<p>For example, ocean models used for climate projections typically look like the one on the left below. But in reality, ocean flow looks much more like the image on the right.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/416444/original/file-20210817-23-1qlczpp.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/416444/original/file-20210817-23-1qlczpp.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=263&fit=crop&dpr=1 600w, https://images.theconversation.com/files/416444/original/file-20210817-23-1qlczpp.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=263&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/416444/original/file-20210817-23-1qlczpp.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=263&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/416444/original/file-20210817-23-1qlczpp.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=330&fit=crop&dpr=1 754w, https://images.theconversation.com/files/416444/original/file-20210817-23-1qlczpp.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=330&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/416444/original/file-20210817-23-1qlczpp.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=330&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Here you can see ocean surface currents modelled at two different resolutions. On the left is a model akin to those typically used for climate projections. The model on the right is much more accurate and realistic, but is unfortunately too computationally restrictive to be used for climate projections.</span>
<span class="attribution"><span class="source">COSIMA</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Unfortunately, we currently don’t have the computational power needed to run high-resolution and realistic climate models for climate projections.</p>
<p>Climate scientists are trying to find ways to incorporate the effects of the fine, small-scale turbulent motions in the above-right image into the coarse-resolution climate model on the left. </p>
<p>If we can do this, we can generate climate projections that are more accurate, yet still computationally feasible. This is what we refer to as “parameterisation” — the holy grail of climate modelling. </p>
<p>Simply, this is when we can achieve a model that doesn’t necessarily include all the smaller-scale complex flow features (which require huge amounts of processing power) — but which can still integrate their effects into the overall model in a simpler and cheaper way.</p>
<h2>A clearer picture</h2>
<p>Some parameterisations already exist in coarse-resolution models, but often don’t do a good job integrating the smaller-scale flow features in an effective way. </p>
<p>Machine learning algorithms can use output from realistic, high-resolution climate models (like the one on the right above) to develop far more accurate parameterisations.</p>
<p>As our computational capacity grows — along with our climate data — we’ll be able to engage increasingly sophisticated machine learning algorithms to sift through this information and deliver improved climate models and projections.</p>
<hr>
<p><iframe src="https://swot.jpl.nasa.gov/gltf_embed/86" width="100%" height="350px" frameborder="0"></p>
<p><em>An interactive model of NASA’s SWOT satellite.</em> </p>
<hr></iframe></p><img src="https://counter.theconversation.com/content/165818/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Navid Constantinou receives funding from the Australian Research Council.</span></em></p>The amount of climate data available to us is growing exponentially, and is far too much to sort through ourselves. But machines can do this for us.Navid Constantinou, ARC DECRA Research Fellow, Australian National UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1656112021-08-08T21:04:04Z2021-08-08T21:04:04ZYes, a few climate models give unexpected predictions – but the technology remains a powerful tool<figure><img src="https://images.theconversation.com/files/415011/original/file-20210806-19-i9a48u.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C5991%2C3098&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>The much-awaited new report from the Intergovernmental Panel on Climate Change (IPCC) is due later today. Ahead of the release, debate has erupted about the computer models at the very heart of global climate projections.</p>
<p>Climate models are one of many tools scientists use to understand how the climate changed in the past and what it will do in future. </p>
<p>A recent <a href="https://www.sciencemag.org/news/2021/07/un-climate-panel-confronts-implausibly-hot-forecasts-future-warming">article</a> in the eminent US magazine Science questioned how the IPCC will deal with some climate models which “run hot”. Some models, it said, have projected global warming rates “that most scientists, including the model makers themselves, believe are implausibly fast”.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/mondays-ipcc-report-is-a-really-big-deal-for-climate-change-so-what-is-it-and-why-should-we-trust-it-165614">Monday's IPCC report is a really big deal for climate change. So what is it? And why should we trust it?</a>
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<p>Some commentators, <a href="https://www.theaustralian.com.au/nation/climate-change-science-magazine-article-blows-the-whistle-on-model-failure/news-story/bf51960ad9a0b7caf3e75843081eef3f">including</a> in <a href="https://www.skynews.com.au/opinion/nasa-comes-clean-about-exaggerated-climate-modelling/video/c462b1a38d061b1ee883cb51ee4c9a2e">Australia</a>, interpreted the article as proof climate modelling had failed. </p>
<p>So should we be using climate models? We are climate scientists from <a href="https://climateextremes.org.au/">Australia’s Centre of Excellence for Climate Extremes</a>, and we believe the answer is a firm yes. </p>
<p>Our research uses and improves climate models so we can help Australia cope with extreme events, now and in future. We know when climate models are running hot or cold. And identifying an error in some climate models doesn’t mean the science has failed – in fact, it means our understanding of the climate system has advanced. </p>
<p>So lets look at what you should know about climate models ahead of the IPCC findings.</p>
<h2>What are climate models?</h2>
<p>Climate models comprise millions of lines of computer code representing the physics and chemistry of the processes that make up our climate system. The models run on powerful supercomputers and have simulated and predicted global warming with <a href="https://www.carbonbrief.org/analysis-how-well-have-climate-models-projected-global-warming">remarkable accuracy</a>. </p>
<p>They unequivocally show that warming of the planet since the Industrial Revolution is due to human-caused emissions of greenhouse gases. This confirms our understanding of the greenhouse effect, <a href="https://theconversation.com/scientists-understood-physics-of-climate-change-in-the-1800s-thanks-to-a-woman-named-eunice-foote-164687">known since the 1850s</a>. </p>
<p>Models also show the intensity of many recent extreme weather events around the world would be <a href="https://www.worldweatherattribution.org/western-north-american-extreme-heat-virtually-impossible-without-human-caused-climate-change/">essentially impossible</a> without this human influence.</p>
<p><div data-react-class="InstagramEmbed" data-react-props="{"url":"https://www.instagram.com/p/BZ38rf7F3al/?utm_source=ig_embed\u0026ig_rid=2f271f3e-3606-477a-8759-dd7b56eb2f51","accessToken":"127105130696839|b4b75090c9688d81dfd245afe6052f20"}"></div></p>
<p>Scientists do not use climate models in isolation, or without considering their limitations.</p>
<p>For a few years now, scientists have known some new-generation climate models probably overestimate global warming, and others underestimate it. </p>
<p>This realisation is based on our understanding of Earth’s climate sensitivity – how much the climate will warm when carbon dioxide (CO₂) levels in the atmosphere double. </p>
<p>Before industrial times, CO₂ levels in the atmosphere were 280 parts per million. So a doubling of CO₂ will occur at 560 parts per million. (For context, we’re <a href="https://www.co2.earth/daily-co2">currently</a> at around 415 parts per million).</p>
<p>The <a href="https://climateextremes.org.au/briefing-note-12-how-sensitive-is-the-earths-temperature-to-the-amount-of-carbon-dioxide-in-the-atmosphere/">latest scientific evidence</a>, using observed warming, paleoclimate data and our physical understanding of the climate system, suggests global average temperatures will very likely increase by between 2.2°C and 4.9°C if CO₂ levels double.</p>
<p>The large majority of climate models run within this climate sensitivity range. But some don’t – <a href="https://www.carbonbrief.org/guest-post-why-low-end-climate-sensitivity-can-now-be-ruled-out">instead suggesting</a> a temperature rise as low as 1.8°C or high as 5.6°C. </p>
<p>It’s thought the biases in some models stem from the <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019GL085782">representations of clouds</a> and their <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2020GL091024">interactions with aerosol particles</a>. Researchers are beginning to understand these biases, building our understanding of the climate system and how to further improve models in future. </p>
<p>With all this in mind, scientists use climate models cautiously, giving more weight to projections from climate models that are consistent with other scientific evidence. </p>
<p>The following graph shows how most models are within the expected climate sensitivity range – and having some running a bit hot or cold doesn’t change the overall picture of future warming. And when we compare model results with the warming we’ve already observed over Australia, there’s no indication the models are over-cooking things.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/415064/original/file-20210807-5434-1g89gjk.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/415064/original/file-20210807-5434-1g89gjk.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/415064/original/file-20210807-5434-1g89gjk.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=268&fit=crop&dpr=1 600w, https://images.theconversation.com/files/415064/original/file-20210807-5434-1g89gjk.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=268&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/415064/original/file-20210807-5434-1g89gjk.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=268&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/415064/original/file-20210807-5434-1g89gjk.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=336&fit=crop&dpr=1 754w, https://images.theconversation.com/files/415064/original/file-20210807-5434-1g89gjk.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=336&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/415064/original/file-20210807-5434-1g89gjk.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=336&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Rapid warming in Australia under a very high greenhouse gas emission future (red) compared with climate change stabilisation in a low emission future (blue). Author provided.</span>
</figcaption>
</figure>
<h2>What does the future look like?</h2>
<p>Future climate projections are produced by giving models different possibilities for greenhouse gas concentrations in our atmosphere. </p>
<p>The latest IPCC models use a set of possibilities called “Shared Socioeconomic Pathways” (<a href="https://www.carbonbrief.org/explainer-how-shared-socioeconomic-pathways-explore-future-climate-change">SSPs</a>). These pathways match expected population growth, and where and how people will live, with plausible levels of atmospheric greenhouse gases that would result from these socioeconomic choices. </p>
<p>The pathways range from low-emission scenarios that also require considerable atmospheric CO₂ removal – giving the world a reasonable chance of meeting the Paris Agreement targets – to high-emission scenarios where temperature goals are far exceeded.</p>
<hr>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/415100/original/file-20210808-17-be6t2h.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/415100/original/file-20210808-17-be6t2h.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/415100/original/file-20210808-17-be6t2h.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=831&fit=crop&dpr=1 600w, https://images.theconversation.com/files/415100/original/file-20210808-17-be6t2h.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=831&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/415100/original/file-20210808-17-be6t2h.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=831&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/415100/original/file-20210808-17-be6t2h.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1044&fit=crop&dpr=1 754w, https://images.theconversation.com/files/415100/original/file-20210808-17-be6t2h.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1044&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/415100/original/file-20210808-17-be6t2h.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1044&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption"></span>
<span class="attribution"><span class="source">Nerilie Abram, based on Riahi et al. 2017</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<hr>
<p>Ahead of the IPCC report, some say the high-emission scenarios are too pessimistic. But likewise, <a href="https://climateextremes.org.au/briefing-note-15-can-we-limit-global-warming-to-1-5c/">it could be argued</a> the lack of climate action over the past decade, and absence of technology to remove large volumes of CO₂ from the atmosphere, means low-emission scenarios are too optimistic. </p>
<p>If countries meet their existing emissions reduction commitments under the Paris Agreement, we can expect to land somewhere in the middle of the scenarios. But the future depends on our choices, and we shouldn’t dismiss any pathway as implausible. </p>
<p>There is considerable value in knowing both the future risks to avoid, and what’s possible under ambitious climate action.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/the-climate-wont-warm-as-much-as-we-feared-but-it-will-warm-more-than-we-hoped-143175">The climate won't warm as much as we feared – but it will warm more than we hoped</a>
</strong>
</em>
</p>
<hr>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/414949/original/file-20210806-21-102net6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Wind turbines in field" src="https://images.theconversation.com/files/414949/original/file-20210806-21-102net6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/414949/original/file-20210806-21-102net6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/414949/original/file-20210806-21-102net6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/414949/original/file-20210806-21-102net6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/414949/original/file-20210806-21-102net6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/414949/original/file-20210806-21-102net6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/414949/original/file-20210806-21-102net6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The future climate depends on our choices today.</span>
<span class="attribution"><span class="source">Unsplash</span></span>
</figcaption>
</figure>
<h2>Where to from here?</h2>
<p>We can expect the IPCC report to be deeply worrying. And unfortunately, 30 years of IPCC history tells us the findings are more likely to be <a href="https://www.sciencedirect.com/science/article/pii/S0959378012001215">too conservative</a> than too alarmist.</p>
<p>An <a href="https://climateextremes.org.au/briefing-note-14-how-might-australia-contribute-to-a-next-generation-global-climate-modelling-facility/">enormous global effort</a> - both scientifically and in computing resources - is needed to ensure climate models can provide even better information.</p>
<p>Climate models are already phenomenal tools at large scales. But increasingly, we’ll need them to produce fine-scale projections to help answer questions such as: where to plant forests to mitigate carbon? Where to build flood defences? Where might crops best be grown? Where would renewable energy resources be best located?</p>
<p>Climate models will continue to be an important tool for the IPCC, policymakers and society as we attempt to manage the unavoidable risks ahead.</p><img src="https://counter.theconversation.com/content/165611/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nerilie Abram receives funding from the Australian Research Council through the Centre of Excellence for Climate Extremes and from the Department of Agriculture, Water and Environment. She is a member of the international Climate Crisis Advisory Group.</span></em></p><p class="fine-print"><em><span>Andrew King receives funding from the Australian Research Council.</span></em></p><p class="fine-print"><em><span>Andy Pitman receives funding from the Australian Research Council through the Centre of Excellence for Climate Extremes and from the ARC Discovery Grants scheme.</span></em></p><p class="fine-print"><em><span>Christian Jakob receives receives funding from the Australian Research Council through the Centre of Excellence for Climate Extremes and from the ARC Discovery Grants scheme.</span></em></p><p class="fine-print"><em><span>Julie Arblaster receives funding from the Australian Research Council and the U.S. Department of Energy</span></em></p><p class="fine-print"><em><span>Lisa Alexander receives funding from the Australian Research Council. </span></em></p><p class="fine-print"><em><span>Sarah Perkins-Kirkpatrick receives funding from the Australian Research Council.</span></em></p><p class="fine-print"><em><span>Shayne McGregor receives funding from Australian Research Council.</span></em></p><p class="fine-print"><em><span>Steven Sherwood receives funding from the Australian Research Council. </span></em></p>An article in the eminent US magazine Science has triggered debate over whether scientists should use climate models. Here’s what you should know about climate models ahead of today’s IPCC report.Nerilie Abram, Chief Investigator for the ARC Centre of Excellence for Climate Extremes; Deputy Director for the Australian Centre for Excellence in Antarctic Science, Australian National UniversityAndrew King, ARC DECRA fellow, The University of MelbourneAndy Pitman, Director of the ARC Centre of Excellence for Climate Extremes, UNSW SydneyChristian Jakob, Professor in Atmospheric Science, Monash UniversityJulie Arblaster, Chief Investigator, ARC Centre of Excellence for Climate Extremes; Chief Investigator, ARC Securing Antarctica's Environmental Future; Professor, Monash UniversityLisa Alexander, Chief Investigator ARC Centre of Excellence for Climate Extremes and Professor Climate Change Research Centre, UNSW SydneySarah Perkins-Kirkpatrick, ARC Future Fellow, UNSW SydneyShayne McGregor, Associate professor, Monash UniversitySteven Sherwood, Professor of Atmospheric Sciences, Climate Change Research Centre, UNSW SydneyLicensed as Creative Commons – attribution, no derivatives.