tag:theconversation.com,2011:/id/topics/climate-projections-26536/articlesClimate projections – The Conversation2023-11-23T01:19:08Ztag: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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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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<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>
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<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>
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<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>
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<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>
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<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>
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<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>
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<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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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>
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<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/2057582023-05-17T10:01:48Z2023-05-17T10:01:48ZGlobal warming to bring record hot year by 2028 – probably our first above 1.5°C limit<p>One year in the next five will almost certainly be the hottest on record and there’s a two-in-three chance a single year will cross the crucial 1.5°C global warming threshold, an alarming <a href="https://public.wmo.int/en/our-mandate/climate/global-annual-decadal-climate-update">new report</a> by the World Meteorological Organization predicts.</p>
<p>The report, known as the <a href="https://public.wmo.int/en/our-mandate/climate/global-annual-decadal-climate-update">Global Annual to Decadal Climate Update</a>, warns if humanity fails to reduce greenhouse gas emissions to net zero, increasingly worse heat records will tumble beyond this decade.</p>
<p>So what is driving the bleak outlook for the next five years? An expected El Niño, on top of the overall global warming trend, will likely push the global temperature to record levels.</p>
<p>Has the Paris Agreement already failed if the global average temperature exceeds the 1.5°C threshold in one of the next five years? No, but it will be a stark warning of what’s in store if we don’t quickly reduce emissions to net zero.</p>
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<img alt="boy plays in fountain during heatwave" src="https://images.theconversation.com/files/526731/original/file-20230517-15-fhpzvb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/526731/original/file-20230517-15-fhpzvb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=409&fit=crop&dpr=1 600w, https://images.theconversation.com/files/526731/original/file-20230517-15-fhpzvb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=409&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/526731/original/file-20230517-15-fhpzvb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=409&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/526731/original/file-20230517-15-fhpzvb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=514&fit=crop&dpr=1 754w, https://images.theconversation.com/files/526731/original/file-20230517-15-fhpzvb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=514&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/526731/original/file-20230517-15-fhpzvb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=514&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">One year in the next five will almost certainly be the hottest on record, bringing more heatwaves like this boy experienced in Britain around the time the last record was set.</span>
<span class="attribution"><span class="source">Andy Rain/EPA</span></span>
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<a href="https://theconversation.com/two-trillion-tonnes-of-greenhouse-gases-25-billion-nukes-of-heat-are-we-pushing-earth-out-of-the-goldilocks-zone-202619">Two trillion tonnes of greenhouse gases, 25 billion nukes of heat: are we pushing Earth out of the Goldilocks zone?</a>
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<h2>Warming makes record heat inevitable</h2>
<p>The World Meteorological Organization update says there is a 98% chance at least one of the next five years will be the hottest on record. And there’s a 66% chance of at least one year over the 1.5°C threshold.</p>
<p>There’s also a 32% chance the average temperature over the next five years will exceed the 1.5°C threshold. The chance of temporarily exceeding 1.5°C has risen steadily since 2015, when it was close to zero. For the years between 2017 and 2021, it was a 10% chance. </p>
<p>Human-caused greenhouse gas emissions have already driven up global average temperatures by more than 1°C since the late 19th century. The update notes the 2022 average global temperature was about 1.15°C above the 1850-1900 average, despite the <a href="http://www.bom.gov.au/climate/updates/articles/a020.shtml">cooling influence of La Niña</a> conditions. Temperatures are now rising by <a href="https://climate.metoffice.cloud/temperature.html">about 0.2°C per decade</a>.</p>
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<span class="caption">Global average surface temperatures relative to 1850-1900 from major datasets. The temperature is increasing by about 0.2°C per decade.</span>
<span class="attribution"><a class="source" href="https://climate.metoffice.cloud/temperature.html">UK Met Office</a></span>
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<p>We now have more than a century of global mean temperature data. That means it should be getting harder, not easier, to achieve new records. If there was no trend, we would expect to see fewer records as time passes and the data we’ve collected better captures the full range of natural climate variability. </p>
<p>Instead, because we are warming the world so quickly, more heat records are being set globally and <a href="https://interactive.carbonbrief.org/half-global-population-saw-all-time-record-temperatures-over-past-decade/">at the local level</a>. The human influence on the climate is pushing temperatures to unprecedented highs with alarming frequency.</p>
<h2>Add El Niño, then extreme highs are likely</h2>
<p>The current record global average temperature <a href="https://theconversation.com/2016-crowned-hottest-year-on-record-australia-needs-to-get-heat-smart-70994">dates back to 2016</a>. A major <a href="http://www.bom.gov.au/climate/updates/articles/a008-el-nino-and-australia.shtml">El Niño event</a> early that year pushed up the global average temperature. </p>
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Read more:
<a href="https://theconversation.com/2016-crowned-hottest-year-on-record-australia-needs-to-get-heat-smart-70994">2016 crowned hottest year on record: Australia needs to get heat smart</a>
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<p>El Niño events are associated with warmer-than-normal seas over much of the central and eastern Pacific. This helps warm the lower atmosphere and raise global temperatures <a href="https://www.realclimate.org/index.php/archives/2023/01/2022-updates-to-the-temperature-records/">by about 0.1°C</a>. This might not sound like much, but with rapid background warming it’s often enough to break the previous record.</p>
<p>In the seven years since the current global temperature record, humanity has continued to intensify the greenhouse effect. This is making a new record ever more likely.</p>
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<p><a href="http://www.bom.gov.au/climate/enso/">El Niño conditions are starting to form</a> in the Pacific and are looking increasingly likely to take hold in June and July. This could be the first significant El Niño since 2016. An El Niño would greatly increase the chance of breaking that year’s record high global average temperature, particularly in 2024. </p>
<h2>Does this mean the Paris Agreement has already failed?</h2>
<p>Almost all nations around the world have signed the <a href="https://unfccc.int/process-and-meetings/the-paris-agreement">Paris Agreement</a>. The aim is to limit global warming to well below 2°C and preferably below 1.5°C above pre-industrial levels. </p>
<p>The prediction that an individual year above 1.5°C global warming is more likely than not is alarming. But it doesn’t mean we have failed to achieve the Paris Agreement’s goals. The agreement aims to limit long-term global warming to a level that avoids major climate impacts, including ecosystem loss. One or two years that pop over the 1.5°C level don’t constitute failure.</p>
<p>However, the world is getting closer to the 1.5°C global warming level due to our <a href="https://theconversation.com/global-carbon-emissions-at-record-levels-with-no-signs-of-shrinking-new-data-shows-humanity-has-a-monumental-task-ahead-193108">continuing high greenhouse gas emissions</a>. The forecast of a probable year that exceeds that level should serve as a warning. </p>
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Read more:
<a href="https://theconversation.com/global-carbon-emissions-at-record-levels-with-no-signs-of-shrinking-new-data-shows-humanity-has-a-monumental-task-ahead-193108">Global carbon emissions at record levels with no signs of shrinking, new data shows. Humanity has a monumental task ahead</a>
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<h2>Yet another sign of humanity’s damage to the climate</h2>
<p>Past inaction on reducing emissions and tackling climate change means we have already <a href="https://globalwarmingindex.org/">warmed the world by more than 1.2°C</a>. Global emissions remain at <a href="https://theconversation.com/global-carbon-emissions-at-record-levels-with-no-signs-of-shrinking-new-data-shows-humanity-has-a-monumental-task-ahead-193108">near-record high levels</a>, so we are continuing to <a href="https://theconversation.com/two-trillion-tonnes-of-greenhouse-gases-25-billion-nukes-of-heat-are-we-pushing-earth-out-of-the-goldilocks-zone-202619">intensify the greenhouse effect</a> and warm the planet. </p>
<p>If we are to limit global warming to well below 2°C, then we must act so future generations don’t suffer a much less hospitable planet.</p>
<p>We have understood the solution for decades. We <a href="https://www.carbonbrief.org/explainer-will-global-warming-stop-as-soon-as-net-zero-emissions-are-reached/">must reduce emissions to net zero</a> to stop warming Earth. Countries such as Australia, with high historical emissions, have a leading role to play by decarbonising electricity supply and ramping down coal, oil and gas production <a href="https://theconversation.com/australias-116-new-coal-oil-and-gas-projects-equate-to-215-new-coal-power-stations-202135">in line with goals laid out by the United Nations</a>.</p>
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Read more:
<a href="https://theconversation.com/australias-116-new-coal-oil-and-gas-projects-equate-to-215-new-coal-power-stations-202135">Australia's 116 new coal, oil and gas projects equate to 215 new coal power stations</a>
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<p>Failure to act should not be considered an option. Otherwise we are locking in more record hot years and <a href="https://theconversation.com/theres-no-end-to-the-damage-humans-can-wreak-on-the-climate-this-is-how-bad-its-likely-to-get-166031">much worse climate change impacts</a> for decades and centuries to come.</p><img src="https://counter.theconversation.com/content/205758/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>There’s a 98% chance of a record hot year by 2028, and a 66% chance of exceeding the 1.5°C threshold for at least that year, according to the latest World Meteorological Organization update.Andrew King, Senior Lecturer in Climate Science, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2017712023-03-17T02:25:27Z2023-03-17T02:25:27ZCyclone Freddy was the most energetic storm on record. Is it a harbinger of things to come?<figure><img src="https://images.theconversation.com/files/515972/original/file-20230317-2475-i50sjb.jpeg?ixlib=rb-1.1.0&rect=129%2C0%2C1408%2C726&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">NOAA / AP</span></span></figcaption></figure><p>On February 4, a storm off the north-west coast of Australia was named Cyclone Freddy. It rapidly strengthened and headed west across the Indian Ocean, eventually causing devastation in eastern Africa. Hundreds of people died, tens of thousands more were displaced, national energy grids were crippled, flash flooding was widespread and <a href="https://reliefweb.int/report/mozambique/southern-africa-tropical-cyclone-freddy-flash-update-no-7-14-march-2023">socioeconomic impacts have been severe</a>.</p>
<p>At its peak on February 21, Freddy had wind gusts of up to 270 km/h, making it a category 5 storm, the highest category on the <a href="https://www.nhc.noaa.gov/aboutsshws.php">Saffir-Simpson scale</a> used to measure cyclone intensity. The following day, Freddy was upgraded further to a “very intense tropical cyclone”, which is science-speak for “off the chart”.</p>
<p>Freddy was the <a href="https://www.reuters.com/world/africa/why-is-cyclone-freddy-record-breaking-storm-2023-03-14/">most energetic storm on record</a>. It also went through the most cycles of weakening and re-intensifying, and may have been the longest-lived cyclone in history.</p>
<p>So was this megastorm a one-off event, or a harbinger of the global warming–fuelled cyclones of the future? And, either way, what does it tell us about preparing for what lies ahead?</p>
<h2>A remarkable journey</h2>
<p>Australia has experienced cyclones in the past with comparable strengths to Freddy. According to the Bureau of Meteorology, <a href="https://en.wikipedia.org/wiki/List_of_Category_5_Australian_region_severe_tropical_cyclones#:%7E:text=Within%20the%20basin%20a%20Category,Australian%20tropical%20cyclone%20intensity%20scale.">48 category-5 tropical cyclones have formed in the Australian region since 1975</a>. That’s about one a year, although most do not cross the coast, or weaken by the time they do.</p>
<p>Cyclone Mahina, which hit Queensland in 1899, is widely considered Australia’s strongest recorded tropical cyclone. Further back in the palaeoclimate record, we find <a href="https://www.nature.com/articles/35097055">evidence of stronger events still</a>.</p>
<p>What was truly remarkable about Freddy was its journey. Freddy was a named tropical cyclone for 39 consecutive days and travelled more than 8,000 kilometres across the entire South Indian Ocean. </p>
<p>It may have been the longest-lasting tropical cyclone on record (this is currently being confirmed by the World Meteorological Organization). The <a href="https://www.myjoyonline.com/wmo-to-set-up-expert-committee-to-determine-possibility-of-tropical-cyclone-freddy-becoming-longest-lasting-on-record/">31-day Hurricane John</a> set the previous record in 1994. </p>
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<a href="https://images.theconversation.com/files/515944/original/file-20230316-19-8gbxs9.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A map of the Indian Ocean showing Cyclone Freddy's path." src="https://images.theconversation.com/files/515944/original/file-20230316-19-8gbxs9.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/515944/original/file-20230316-19-8gbxs9.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=371&fit=crop&dpr=1 600w, https://images.theconversation.com/files/515944/original/file-20230316-19-8gbxs9.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=371&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/515944/original/file-20230316-19-8gbxs9.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=371&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/515944/original/file-20230316-19-8gbxs9.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=466&fit=crop&dpr=1 754w, https://images.theconversation.com/files/515944/original/file-20230316-19-8gbxs9.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=466&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/515944/original/file-20230316-19-8gbxs9.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=466&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">Over 39 days in February and March 2023, Cyclone Freddy travelled more than 8,000 kilometres from the Timor Sea to the east coast of Africa.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Cyclone_Freddy#/media/File:Freddy_2023_path.png">Meow / Wikimedia / NASA / NRL / NOAA</a></span>
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<p>Freddy appears to have had an accumulated cyclone energy (the index used to measure the energy released by a tropical cyclone over its lifetime) <a href="https://public.wmo.int/en/media/news/tropical-cyclone-freddy-may-set-new-record">equivalent to an average full North Atlantic hurricane season</a>.</p>
<h2>Was Cyclone Freddy driven by climate change?</h2>
<p>It’s no easy task to join the dots between climate change and any given extreme weather event, such as a cyclone or heatwave. </p>
<p>A relatively new area of study called “<a href="https://www.worldweatherattribution.org/">climate attribution science</a>” attempts to do it by determining how much more likely a given event was in today’s climate compared to the past climate.</p>
<p>The main idea in attribution science is to model extreme weather events under present-day climate conditions, and then do it again when the model is run with no human-made greenhouse gases in the atmosphere. This process is repeated many times to try to understand the likelihood of a weather event occurring with and without human-driven warming.</p>
<p>To date, these studies have had most success with large-scale, slow-moving extreme weather events – like the <a href="https://www.pnas.org/doi/10.1073/pnas.2112087118">February 2019 European heatwave</a>. The jury is still out on how well we can do this for tropical cyclones.</p>
<p>So we can’t yet say what role climate change may have played in making a cyclone like Freddy more likely, but the science is moving fast.</p>
<h2>The future of cyclones: fewer, slower, stronger</h2>
<p>Cyclone behaviour is already changing, and our climate models project it will change more in the future. </p>
<p>In many parts of the world, the number of cyclones making landfall is on the rise. In Australia, however, this number is decreasing – and most climate models indicate <a href="https://www.nature.com/articles/s41558-022-01388-4">this decrease will likely continue</a> under a warming climate. This is related to the weakening of Pacific atmospheric circulation, which is less favourable for the formation of tropical cyclones.</p>
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<strong>
Read more:
<a href="https://theconversation.com/research-shows-tropical-cyclones-have-decreased-alongside-human-caused-global-warming-but-dont-celebrate-yet-185706">Research shows tropical cyclones have decreased alongside human-caused global warming – but don't celebrate yet</a>
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<p>This is good news for Australia, although other changes in projected cyclone behaviour may give us less cause for optimism.</p>
<p>While the total number of cyclones may decrease, research indicates those that do make landfall <a href="https://nespclimate.com.au/wp-content/uploads/2019/11/A4_4pp_brochure_NESP_ESCC_Tropical_Cyclones_FINAL_Nov11_2019_WEB.pdf">may be stronger</a>. Other research indicates cyclones may be <a href="https://www.nature.com/articles/s41586-018-0158-3">moving more slowly</a> and also <a href="https://www.nature.com/articles/s41561-021-00859-1">roaming farther from the equator</a>. The amount of rain any one cyclone can hold will also <a href="https://www.nature.com/articles/s41467-021-25685-2">likely increase</a> in a warming atmosphere.</p>
<p>All these changes would increase cyclone risk on the east coast of Australia. However, these projections are uncertain. The only discernible trend so far is a reduction in overall cyclone frequency.</p>
<h2>The influence of La Nina</h2>
<p>Australia is famously a land of droughts and flooding rains. Regardless of underlying trends, large swings in climate conditions are common from year to year.</p>
<p>In Australia, most cyclone (and flood) impacts occur during La Nina periods: <a href="https://aoninsights.com.au/say-goodbye-to-the-big-wet-and-excessive-losses/">over 60% of cyclone losses and 75% of insured flood losses</a>. </p>
<p>The La Nina period that has just ended meant the waters of the tropical East Indian Ocean were warmer than usual. This extra heat may have sustained Freddy in its trans-oceanic journey. </p>
<p>Similarly, a <a href="https://www.reuters.com/world/asia-pacific/new-zealands-southern-waters-experiencing-marine-heatwave-2023-01-16/#:%7E:text=The%20marine%20heatwave%20comes%20as,the%20heatwave%2C%20said%20de%20Souza.">marine heatwave</a> in the Southwest Pacific contributed to the lifetime and amount of rain produced by ex-tropical cyclone Gabrielle in New Zealand in February.</p>
<h2>Building for the future</h2>
<p>Cyclone impacts are traditionally hit-and-miss affairs in Australia. We can get a category 5 cyclone screaming through north-western WA and only a few cattle really know about it.</p>
<p>However, as population increases, the number of people in harm’s way also potentially increases. No matter how cyclones may change in the future, we need to ensure resilience is a core feature in building future housing stock.</p>
<p>In Australia, it is encouraging to see more government emphasis on reducing disaster risk (rather then just cleaning up afterwards), through frameworks such as the <a href="https://nema.gov.au/disaster-ready-fund">Disaster Ready Fund</a>.</p>
<p>Elsewhere, we should throw our support behind resilience programs in the Global South like those in countries hit by Freddy, where vulnerabilities remain high.</p><img src="https://counter.theconversation.com/content/201771/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Thomas Mortlock works for Aon Reinsurance Solutions</span></em></p>The record-breaking Cyclone Freddy was a wake-up call to prepare for the storms of the future.Thomas Mortlock, Adjunct Fellow, UNSW SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1975262023-01-11T19:07:50Z2023-01-11T19:07:50ZWhat does climate change mean for extreme waves? In 80% of the world, we don’t really know<figure><img src="https://images.theconversation.com/files/503958/original/file-20230111-448-g2wsq8.jpeg?ixlib=rb-1.1.0&rect=39%2C0%2C4409%2C2937&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>Across much of the world’s oceans, waves are getting bigger. In the Southern Ocean, where storm-driven swell can propagate halfway across the world to California, the average wave has grown about 20cm in the past 30 years.</p>
<p>These changes are part of climate change, and are likely to continue well into the future. If you’re making long-term plans near the sea – like building ships, or constructing flood defences in coastal cities – you need more detail about how big those waves are going to get.</p>
<p>In a <a href="https://doi.org/10.1126/sciadv.ade3170">study</a> published today in Science Advances, we looked at the projected changes in the size of the very biggest waves around the globe. We found the uncertainties in the projections could be larger than the projected future changes themselves in about 80% of the world’s oceans and coastlines.</p>
<h2>The ‘wave climate’</h2>
<p>My group and I study the world’s “wave climate”: the size and distribution of ocean waves in different places, and how that has changed in the past and will change in the future.</p>
<p>We’re interested in the heights of average waves, but also the extreme conditions. As with floods or heatwaves, extreme waves are the ones that cause problems – so they’re often the ones we need to know about when we’re building near the sea.</p>
<p>From floating buoys and satellite radar, we have records of wave heights extending back 30 to 40 years. These data don’t cover the whole world, but we feed them into computer models that fill in the gaps. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/503961/original/file-20230111-4890-1qpfqc.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An aerial photo of waves rolling in to shore." src="https://images.theconversation.com/files/503961/original/file-20230111-4890-1qpfqc.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/503961/original/file-20230111-4890-1qpfqc.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/503961/original/file-20230111-4890-1qpfqc.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/503961/original/file-20230111-4890-1qpfqc.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/503961/original/file-20230111-4890-1qpfqc.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/503961/original/file-20230111-4890-1qpfqc.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/503961/original/file-20230111-4890-1qpfqc.jpeg?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>
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<span class="caption">Waves are driven by winds over the surface of the ocean.</span>
<span class="attribution"><span class="source">Dan Grinwis</span></span>
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</figure>
<p>Waves are created by the wind, so our models of waves are also tied to what we know about wind conditions. Taken all together, we have about 40 years of model data giving wave conditions for the whole world’s oceans (broken up into “pixels” about 25 kilometres across).</p>
<p>We also use a branch of statistics called extreme value analysis to calculate things like the biggest wave you can expect at a given location once in 100 years (the 100-year event).</p>
<h2>Why waves are changing</h2>
<p>As the climate changes, we expect that global wind patterns will change – so the world’s waves will change as well. </p>
<p>One change we are already seeing is that many low-pressure systems, which create high winds, are becoming more intense and moving away from the equator and towards the poles. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/climate-change-may-change-the-way-ocean-waves-impact-50-of-the-worlds-coastlines-121239">Climate change may change the way ocean waves impact 50% of the world’s coastlines</a>
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<p>In the southern hemisphere, this means more high winds over the Southern Ocean, driving bigger waves. This swell in the Southern Ocean propagates out into the Pacific, Atlantic and Indian oceans – which means bigger waves across the southern hemisphere.</p>
<p>Indeed, we have observed that average wave heights in the Southern Ocean have increased by around 20cm over the past 30 years.</p>
<p>In the northern hemisphere, there is more land closer to the pole. So the high winds are now more often happening over land, and ocean waves are actually losing some height. </p>
<h2>A blurry future</h2>
<p>So what does all this mean for the future? In our new study, we tried to figure that out.</p>
<p>To get an idea of the future of waves, we start with wind projections from major climate models that are used to project future temperatures as carbon dioxide levels in the atmosphere increase. We then feed these winds into our wave models, and see what they predict.</p>
<p>There are many wind and wave models, all with slight differences in their assumptions and the way they model the physics, so they all produce somewhat different projections. We combined the results from an ensemble of a dozen models to get a clearer picture of the differences.</p>
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<a href="https://images.theconversation.com/files/503959/original/file-20230111-4926-ngzmq6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An aerial photo of waves crashing on a coastline." src="https://images.theconversation.com/files/503959/original/file-20230111-4926-ngzmq6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/503959/original/file-20230111-4926-ngzmq6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/503959/original/file-20230111-4926-ngzmq6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/503959/original/file-20230111-4926-ngzmq6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/503959/original/file-20230111-4926-ngzmq6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=565&fit=crop&dpr=1 754w, https://images.theconversation.com/files/503959/original/file-20230111-4926-ngzmq6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=565&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/503959/original/file-20230111-4926-ngzmq6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=565&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">Waves shape coastlines through erosion.</span>
<span class="attribution"><span class="source">Dan Grinwis</span></span>
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<p>On average, we found extreme wave heights in many places are likely to grow by between 5% and 8% by 2100.</p>
<p>However, there is a lot of uncertainty in those estimates. One source of uncertainty is how much carbon dioxide humans pump into the atmosphere over the coming decades. </p>
<p>Another source is the uncertainty in the models themselves. We found that in many cases the difference in estimates between different models was about the same size as the projected changes in wave height.</p>
<h2>A note of caution</h2>
<p>The upshot of our research is that there is still a lot of uncertainty in what will happen to the size of extreme waves in the coming decades. That means there is also a lot of uncertainty in our projections of coastal flooding and the erosion of beaches.</p>
<p>These uncertainties may not seem huge – perhaps 30-40cm by 2100 – but they’re big enough to determine whether or not a particular coastal property ends up underwater.</p>
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Read more:
<a href="https://theconversation.com/curious-kids-why-are-there-waves-112015">Curious Kids: why are there waves?</a>
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<p>So for anyone making plans near the sea – like engineers designing coastal structures, governments building flood defences, or local councils making development decisions – the message is that you should err on the side of caution in your decision-making. </p>
<p>For the rest of us, it’s a reminder that climate change doesn’t just mean rising temperatures: it means a transformation of the whole global climate system, in ways we still don’t fully understand.</p><img src="https://counter.theconversation.com/content/197526/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ian Young receives funding from the Australian Research Council, the Victorian Government through DELWP and the Integrated Marine Observing System. </span></em></p>Sea-level rise isn’t the only climate-related problem for our coasts – extreme waves that cause flooding and erosion are also changing, but exactly how is hard to predict.Ian Young, Kernot Professor of Engineering, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1886402022-08-16T15:00:24Z2022-08-16T15:00:24ZInfluential oil company scenarios for combating climate change don’t actually meet the Paris Agreement goals, our new analysis shows<figure><img src="https://images.theconversation.com/files/479255/original/file-20220816-20495-lz4b8o.jpg?ixlib=rb-1.1.0&rect=67%2C116%2C2928%2C1877&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">BP, Shell and Equinor all produce widely used scenarios of energy's future.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/s-huge-oil-refinery-complex-continues-its-24-hour-news-photo/52204994">Christopher Furlong/Getty Images</a></span></figcaption></figure><p>Several major oil companies, including BP and Shell, periodically publish scenarios forecasting the future of the energy sector. In recent years, they have added visions for how climate change might be addressed, including scenarios that they claim are consistent with the international Paris climate agreement.</p>
<p>These scenarios are hugely influential. They are used by companies making investment decisions and, importantly, by policymakers as a basis for their decisions.</p>
<p>But <a href="https://www.carbonbrief.org/analysis-shell-says-new-brazil-sized-forest-would-be-needed-to-meet-1-5c-climate-goal/">are they really compatible</a> with the Paris Agreement?</p>
<p>Many of the future scenarios show continued reliance on fossil fuels. But data gaps and a lack of transparency can make it difficult to compare them with independent scientific assessments, such as the global reviews <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-3/">by the Intergovernmental Panel on Climate Change</a>.</p>
<p>In a <a href="https://www.nature.com/articles/s41467-022-31734-1">study</a> published Aug. 16, 2022, in Nature Communications, our international team analyzed four of these scenarios and two others by the International Energy Agency using a new method we developed for comparing such energy scenarios head-to-head. We determined that five of them – including frequently cited scenarios from <a href="https://www.bp.com/en/global/corporate/energy-economics/energy-outlook/overview.html">BP</a>, <a href="https://www.shell.com/energy-and-innovation/the-energy-future/scenarios.html">Shell</a> and <a href="https://www.equinor.com/sustainability/energy-perspectives">Equinor</a> – were not consistent with the Paris goals.</p>
<h2>What the Paris Agreement expects</h2>
<p>The <a href="https://unfccc.int/process-and-meetings/the-paris-agreement/the-paris-agreement">2015 Paris Agreement</a>, signed by nearly all countries, sets out <a href="https://www.carbonbrief.org/guest-post-why-1-5c-and-well-below-2c-are-part-and-parcel-of-one-temperature-goal/">a few criteria</a> to meet its objectives.</p>
<p>One is to ensure the global average temperature increase stays well below 2 degrees Celsius (3.6 F) compared to pre-industrial era levels, and to pursue efforts to keep warming under 1.5°C (2.7 F). The agreement also states that global emissions should peak as soon as possible and reach at least <a href="https://www.un.org/en/climatechange/net-zero-coalition">net zero</a> greenhouse gas emissions in the second half of the century. Pathways that meet these objectives show that carbon dioxide emissions should fall even faster, reaching net zero by about 2050. </p>
<p>Scientific evidence shows that overshooting 1.5°C of warming, even temporarily, would have harmful <a href="https://climateanalytics.org/publications/2021/the-science-of-temperature-overshoots-impacts-uncertainties-and-implications-for-near-term-emissions-reductions/">consequences for the global climate</a>. Those consequences are not necessarily reversible, and it’s unclear how well people, ecosystems and economies would <a href="https://theconversation.com/transformational-change-is-coming-to-how-people-live-on-earth-un-climate-adaptation-report-warns-which-path-will-humanity-choose-177604">be able to adapt</a>.</p>
<h2>How the scenarios perform</h2>
<p>We have been working with the nonprofit science and policy research institute <a href="https://climateanalytics.org/">Climate Analytics</a> to better understand the implications of the Paris Agreement for <a href="http://1p5ndc-pathways.climateanalytics.org/">global and national</a> decarbonization pathways – the paths countries can take to cut their greenhouse gas emissions. In particular, we have explored the roles that <a href="https://climateanalytics.org/briefings/coal-phase-out/">coal</a> and <a href="https://climateanalytics.org/latest/report-why-gas-is-the-new-coal/">natural gas</a> can play as the world transitions away from fossil fuels.</p>
<p>When we analyzed the energy companies’ decarbonization scenarios, we found that <a href="https://www.bp.com/en/global/corporate/energy-economics/energy-outlook/overview.html">BP</a>’s, <a href="https://www.shell.com/energy-and-innovation/the-energy-future/scenarios.html">Shell</a>’s and <a href="https://www.equinor.com/sustainability/energy-perspectives">Equinor</a>’s scenarios overshoot the 1.5°C limit of the Paris Agreement by a significant margin, with only <a href="https://www.bp.com/en/global/corporate/energy-economics/energy-outlook/overview.html">BP</a>’s having a greater than 50% chance of subsequently drawing temperatures down to 1.5°C by 2100. </p>
<p>These scenarios also showed higher near-term use of coal and long-term use of gas for electricity production than Paris-compatible scenarios, such as those assessed by the IPCC. Overall, the energy company scenarios also feature higher levels of carbon dioxide emissions than Paris-compatible scenarios. </p>
<p>Of the six scenarios, we determined that only the International Energy Agency’s <a href="https://www.iea.org/reports/net-zero-by-2050">Net Zero by 2050</a> scenario sketches out an energy future that is compatible with the 1.5°C Paris Agreement goal.</p>
<p>We found this scenario has a greater than 33% chance of keeping warming from ever exceeding 1.5°C, a 50% chance of having temperatures 1.5°C warmer or less in 2100, and a nearly 90% chance of keeping warming always below 2°C. This is in line with the criteria we use to assess <a href="https://www.carbonbrief.org/guest-post-why-1-5c-and-well-below-2c-are-part-and-parcel-of-one-temperature-goal/">Paris Agreement consistency</a>, and also in line with the approach taken in the IPCC’s <a href="https://www.ipcc.ch/sr15/chapter/spm/">Special Report on 1.5°C</a>, which highlights pathways with no or limited overshoot to be 1.5°C compatible.</p>
<p><iframe id="YRlxE" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/YRlxE/9/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<h2>Getting the right picture of decarbonization</h2>
<p>When any group publishes future energy scenarios, it’s useful to have a transparent way to make an apples-to-apples comparison and evaluate the temperature implications. Most of the corporate scenarios, with the exception of Shell’s Sky 1.5 scenario, don’t extend beyond midcentury and focus on carbon dioxide without assessing other greenhouse gases. </p>
<p>Our method uses a transparent procedure to extend each pathway to 2100 and estimate emissions of other gases, which allows us to calculate the temperature outcomes of these scenarios using <a href="https://www.carbonbrief.org/guest-post-the-role-emulator-models-play-in-climate-change-projections/">simple climate models</a>.</p>
<p>Without a consistent basis for comparison, there is a risk that policymakers and businesses will have an inaccurate picture about the pathways available for decarbonizing economies.</p>
<p>Meeting the 1.5°C goal will be challenging. The planet has already warmed about <a href="https://earthobservatory.nasa.gov/world-of-change/global-temperatures">1.1°C since pre-industrial times</a>, and people are suffering through deadly heat waves, droughts, wildfires and extreme storms linked to climate change. There is little room for false starts and dead-ends as countries transform their energy, agricultural and industrial systems on the way to net-zero greenhouse gas emissions.</p><img src="https://counter.theconversation.com/content/188640/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Robert Brecha is affiliated with Climate Analytics in Berlin, Germany. </span></em></p><p class="fine-print"><em><span>Gaurav Ganti is affiliated with Climate Analytics in Berlin, Germany.</span></em></p>Most claiming to be compatible with the climate agreement show a strong continuing reliance on natural gas and coal.Robert Brecha, Professor of Sustainability, University of DaytonGaurav Ganti, Ph.D. Student in Geography, Humboldt University of BerlinLicensed 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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<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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<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/1715012021-11-10T02:23:03Z2021-11-10T02:23:03ZThe fate of our planet depends on the next few days of complex diplomacy in Glasgow. Here’s what needs to go right<p>A new, grim projection, released overnight by <a href="https://climateactiontracker.org/publications/glasgows-2030-credibility-gap-net-zeros-lip-service-to-climate-action/">Climate Action Tracker</a>, has dashed the cautious optimism following last week’s commitments at the UN climate talks in Glasgow. It found the world is still headed for 2.1°C of warming this century, even if all pledges are met.</p>
<p>Similar new analysis from <a href="https://climateanalytics.org/publications/2021/15c-remains-out-of-reach-in-the-ieas-announced-pledges-scenario/">Climate Analytics</a> suggests if global warming is to be limited to 1.5°C, an enormous ambition gap remains for this decade.</p>
<p>Last week, national leaders shared their plans to cut carbon pollution and to transition to a net-zero emissions economy. Some countries made much more ambitious commitments than others. The UK for example, as summit hosts, pledged to cut emissions by 68% this decade, while Australia – a clear laggard among developed countries – refused to strengthen the target it set in 2015 to cut emissions by 26-28% by 2030. </p>
<p>Taken together, national announcements clarify that the world has made some progress since the 2015 Paris climate summit, but not nearly enough to avoid climate catastrophe. So what needs to happen in the final days of frantic negotiations at COP26 to close the ambition gap? </p>
<h2>Global ambition in this decisive decade</h2>
<p>While most world leaders have headed home, negotiators remain locked in late night talks aimed at securing a “Glasgow Package”, including a final political outcome that will keep the goals of the Paris Agreement in reach. Their discussions are now focused on achieving a political outcome that will accelerate climate action this decade. </p>
<p>The 2015 Paris Agreement requires countries to set new and more ambitious targets to reduce emissions every five years, and national pledges aren’t due again until 2025. But if the world is to keep the Paris Agreement goal of limiting global warming to 1.5°C in reach, countries will need to increase ambition before then.</p>
<p>More than 100 countries are calling for strengthened ratchet mechanisms to be established in Glasgow, which could require countries like Australia to set a new 2030 target as soon as next year. These proposals have support from major powers, including the United States, but achieving consensus for an ambitious Glasgow package will be a tough ask.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/431220/original/file-20211110-15-3a3sc9.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/431220/original/file-20211110-15-3a3sc9.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/431220/original/file-20211110-15-3a3sc9.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=491&fit=crop&dpr=1 600w, https://images.theconversation.com/files/431220/original/file-20211110-15-3a3sc9.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=491&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/431220/original/file-20211110-15-3a3sc9.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=491&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/431220/original/file-20211110-15-3a3sc9.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=617&fit=crop&dpr=1 754w, https://images.theconversation.com/files/431220/original/file-20211110-15-3a3sc9.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=617&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/431220/original/file-20211110-15-3a3sc9.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=617&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">The current 2030 targets (without long-term pledges) put us on track for a 2.4°C temperature increase by the end of the century.</span>
<span class="attribution"><span class="source">Climate Action Tracker</span></span>
</figcaption>
</figure>
<p>The good news is countries have committed to greater climate action than they did in 2015. This provides hope that the Paris Agreement – which requires stronger commitments over time – is working. </p>
<p>Last week, <a href="https://www.iea.org/commentaries/cop26-climate-pledges-could-help-limit-global-warming-to-1-8-c-but-implementing-them-will-be-the-key">projections from the International Energy Agency</a> suggested that, if they are fully funded and implemented, Glasgow commitments give the world a 50% chance to limit warming to 1.8°C this century. </p>
<p>But the bad news? This is a big “if”. As it is, Earth is still on track for catastrophic warming. Emissions are projected to <a href="https://www.globalcarbonproject.org/carbonbudget/21/highlights.htm">rebound strongly in 2021</a> (after an unprecedented drop in 2020 because of the global pandemic). </p>
<p>Indeed, alongside the sobering findings overnight that we’re still on track for at least 2.1°C global warming, the UN Environment Programme <a href="https://wedocs.unep.org/bitstream/handle/20.500.11822/37350/AddEGR21.pdf?sequence=3&isAllowed=y">updated its Emissions Gap Report</a>. Taking last week’s pledges into account, it found we’re on track to reduce global emissions by just 8% by 2030, falling well short of the 55% reduction needed to keep global warming to below 1.5°C.</p>
<p>Limiting warming to 1.5°C this century is key to avoiding the worst impacts of climate change, and is a matter of survival for some Pacific island nations. </p>
<p>In Glasgow, groupings of countries at the frontline of climate change – including 55 members of the <a href="https://thecvf.org/our-voice/statements/dhaka-glasgow-declaration-of-the-cvf/">Climate Vulnerable Forum</a>, 48 <a href="http://www.ldc-climate.org/press_release/least-developed-countries-call-for-scaled-up-climate-action-and-support-despite-hiatus-from-un-climate-talks/">Least Developed Countries</a>, and 39 members of the <a href="https://www.aosis.org/aosis-statement-at-cop26-world-leaders-summit/">Alliance of Small Island States</a> – have put forward proposals that would require accelerated emissions cuts this decade. </p>
<p>These proposals have won support from key developed nations, including the United States, as part of the <a href="https://www.highambitioncoalition.org/">High Ambition Coalition</a> – a grouping of countries that unites developed and developing nations which have traditionally not acted in concert. </p>
<p>This coalition was crucial to securing the 2015 Paris Agreement. Last week, it <a href="https://www.highambitioncoalition.org/statements/cochair-summary-april-2021-9n7c5-z7kxl-733k4-49h35">stressed</a> the need to halve global emissions by 2030, and called on parties to deliver more ambitious national commitments well before COP27 “in line with a 1.5°C trajectory”.</p>
<p>This provides renewed hope Glasgow will deliver a political outcome that will require countries to ratchet up short-term climate action. </p>
<h2>Finding a ‘landing zone’ for a Glasgow deal</h2>
<p>The COP26 presidency has tasked the nations of Grenada and Denmark with finding a landing zone for a Glasgow decision that would “keep 1.5°C alive”. In October, Denmark released a <a href="https://unfccc.int/sites/default/files/resource/summary%20from%20informal%20ministerial%20consultations%20on%20keeping%201.5c%20alive.pdf">summary</a> of consultations they held with country negotiators to that point.</p>
<p>It provided options including:</p>
<ul>
<li><p>a requirement for countries that have not yet submitted enhanced targets to do so in 2022</p></li>
<li><p>an annual review of pre-2030 ambition</p></li>
<li><p>a leaders-level event to consider 2030 ambition.</p></li>
</ul>
<p>All these options made it to <a href="https://unfccc.int/sites/default/files/resource/Non-paper%20on%20possible%20elements.pdf">an early draft</a> of the Glasgow final decision text released at the weekend, and a new draft is expected on Wednesday morning (Glasgow time). </p>
<p>However, significant differences between countries remain, and negotiators will now try to hammer out a final political outcome. Saudi Arabia, for example, has <a href="https://www.greenpeace.org/international/press-release/50547/cop26-saudi-arabia-negotiators-cripple/">already tried</a> to head off an ambitious commitment to new action before 2030. </p>
<p>The Australian government might have been cheering Saudi Arabia from the sidelines. Australia is the only advanced economy that didn’t bring a strengthened 2030 target to Glasgow. An ambitious political statement in the COP26 decision text could require the federal government to set new 2030 targets – and devise policy to meet them – as soon as next year.</p>
<h2>Reaching consensus</h2>
<p>The UN climate talks are built on consensus among 190-odd countries. Achieving meaningful outcomes is a diplomatic balancing act built on trust among negotiating parties. </p>
<p>Central to building trust is a commitment by wealthy nations to provide climate finance, to help developing countries deal with the impacts of climate change and to transition to low-emissions development. </p>
<p>More than a decade ago, wealthy nations promised the developing world they would provide US$100 billion per year by 2020. So far they have failed to deliver on this promise.</p>
<p>However, US climate envoy John Kerry <a href="https://www.reuters.com/business/environment/japan-pledge-brings-100-bln-climate-funding-target-closer-us-envoy-says-2021-11-02/">says rich nations will meet the goal by 2022</a> (and exceed it over the 2020-2025 period). </p>
<p>Wary of broken promises, developing countries are looking for renewed commitments on climate finance, especially for the period after 2025. Countries most clearly in the firing line of climate impacts are also pressing for finance to compensate for unavoidable loss and damage.</p>
<p>Progress in the UN climate talks, both at COP26 and beyond, may involve a “grand bargain” encompassing new promises on climate finance from wealthy countries, and new commitments to reduce emissions from both developed and developing countries. </p>
<p>It is no overstatement to say the fate of our planet depends on the next few days of complex multilateral diplomacy in Glasgow.</p>
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<img alt="COP26: the world's biggest climate talks" src="https://images.theconversation.com/files/424739/original/file-20211005-17-cgrf2z.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/424739/original/file-20211005-17-cgrf2z.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/424739/original/file-20211005-17-cgrf2z.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/424739/original/file-20211005-17-cgrf2z.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/424739/original/file-20211005-17-cgrf2z.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/424739/original/file-20211005-17-cgrf2z.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/424739/original/file-20211005-17-cgrf2z.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>This story is part of The Conversation’s coverage on COP26, the Glasgow climate conference, by experts from around the world.</strong>
<br><em>Amid a rising tide of climate news and stories, The Conversation is here to clear the air and make sure you get information you can trust. <a href="https://page.theconversation.com/cop26-glasgow-2021-climate-change-summit/"><strong>More.</strong></a></em> </p>
<hr><img src="https://counter.theconversation.com/content/171501/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Wesley Morgan is a Researcher with the Climate Council</span></em></p>A new climate projection found Glasgow pledges leave the world off-track for limiting warming to 1.5°C. What needs to happen in the final days of frantic COP26 negotiations to close the ambition gap?Wesley Morgan, Research Fellow, Griffith Asia Institute and Climate Council researcher, Griffith UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1080652019-08-19T20:02:14Z2019-08-19T20:02:14ZWe built a network of greenhouses and rain shelters to simulate what climate change will do to soils<figure><img src="https://images.theconversation.com/files/288473/original/file-20190819-123727-1t6cd6l.jpeg?ixlib=rb-1.1.0&rect=1%2C0%2C997%2C667&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Mimicking the future.</span> <span class="attribution"><span class="source">Joe Fontaine</span>, <span class="license">Author provided</span></span></figcaption></figure><p>As most of the science community knows, the climate emergency is here now. Weather extremes such as droughts and heatwaves are increasing in frequency and intensity and are measurably exacerbated by climate change. The significant impacts of these extremes are well documented on both our <a href="https://theconversation.com/are-more-aussie-trees-dying-of-drought-scientists-need-your-help-spotting-dead-trees-113756">native terrestrial</a> and <a href="https://theconversation.com/extreme-weather-caused-by-climate-change-has-damaged-45-of-australias-coastal-habitat-120671">marine</a> ecosystems.</p>
<p>Less documented is what’s happening beneath our feet. Changes below the ground are hard to measure, so most previous research has focused on what can be readily observed above the ground, such as tree deaths.</p>
<p>But soil is a crucial element of the climate system, being the <a href="https://www.eea.europa.eu/signals/signals-2015/articles/soil-and-climate-change">second-largest store of carbon</a> after the ocean. Climate change can result either in an increase in soil carbon storage (through plant growth), or in more carbon being released into the atmosphere (through plant death). Soil is also full of microbes such as fungi, bacteria and algae, and these organisms play a vital role in determining how well an ecosystem functions and how it responds to changes in climate.</p>
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Read more:
<a href="https://theconversation.com/eyes-down-how-setting-our-sights-on-soil-could-help-save-the-climate-51514">Eyes down: how setting our sights on soil could help save the climate</a>
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<p>We have <a href="https://doi.org/10.1016/j.scitotenv.2019.05.222">completed one of the first studies</a> to examine the impact of drought and warmer temperatures on living organisms below the ground (known as the soil biota), in biodiverse shrublands in Western Australia, near Eneabba, about 280km north of Perth. These areas are already suffering immense climate-related stress above ground as a result of rising temperatures and longer droughts. This is making these ecosystems extremely vulnerable with many plant species facing likely extinctions in the future. </p>
<p>We documented significant impacts for soil biota too, with implications for the health of ecosystems in regions that are expected to experience increased drought and climate warming in the future.</p>
<p>We found that lower rainfall and higher temperatures are likely to affect the overall composition of soil fungal communities, and that some groups may be lost altogether.</p>
<p>We saw an increase in the number of fungal species that cause plant disease, whereas many common and beneficial fungi declined in response to warming and drying. These beneficial fungi contribute to many important ecosystem processes, such as boosting plant growth, and ensuring that plants get enough water and nutrients such as phosphorus.</p>
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<a href="https://images.theconversation.com/files/288307/original/file-20190816-192219-pgefmv.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/288307/original/file-20190816-192219-pgefmv.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/288307/original/file-20190816-192219-pgefmv.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/288307/original/file-20190816-192219-pgefmv.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/288307/original/file-20190816-192219-pgefmv.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/288307/original/file-20190816-192219-pgefmv.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/288307/original/file-20190816-192219-pgefmv.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/288307/original/file-20190816-192219-pgefmv.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>
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<span class="caption">Western Australia’s shrublands are already suffering climate stress.</span>
<span class="attribution"><span class="source">Joe Fontaine</span>, <span class="license">Author provided</span></span>
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<h2>How we did it</h2>
<p>We built specially constructed shelters and mini-greenhouses over plots of shrubland 4x4m in size, to recreate the drier, hotter weather conditions predicted to arise between now and the end of the 21st century. This allowed us to assess how the projected future climate will affect the composition, richness and diversity of soil fungi.</p>
<p>Our rain shelters consisted of a roof made of gutters, widely spaced so as to intercept about 30% of the rain that fell on the plot and funnel it away.</p>
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Read more:
<a href="https://theconversation.com/we-need-more-carbon-in-our-soil-to-help-australian-farmers-through-the-drought-102991">We need more carbon in our soil to help Australian farmers through the drought</a>
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<p>To study the impact of increased temperature, we enclosed separate plots on the same sites in walls made of transparent fibreglass sheeting. These worked in a similar way to a greenhouse, by reducing air flow and increasing daytime temperatures inside the shelter by 5.5°C. </p>
<p>We left the rain shelters and mini-greenhouses in place for four years. Then we collected soil from each plot and examined the fungi in the soil using DNA sequencing techniques. </p>
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<a href="https://images.theconversation.com/files/288306/original/file-20190816-192219-z5s03k.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/288306/original/file-20190816-192219-z5s03k.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/288306/original/file-20190816-192219-z5s03k.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/288306/original/file-20190816-192219-z5s03k.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/288306/original/file-20190816-192219-z5s03k.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/288306/original/file-20190816-192219-z5s03k.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/288306/original/file-20190816-192219-z5s03k.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/288306/original/file-20190816-192219-z5s03k.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>
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<span class="caption">How to engineer an artificial drought.</span>
<span class="attribution"><span class="source">Joe Fontaine</span>, <span class="license">Author provided</span></span>
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<p>Our study revealed that it is vital to understand patterns of below-ground ecosystems as well as those we can see, if we are to accurately predict how our shrublands and other valuable ecosystems will be altered by climate change.</p><img src="https://counter.theconversation.com/content/108065/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Joe Fontaine receives funding from the Australian Research Council. </span></em></p><p class="fine-print"><em><span>Neal Enright receives funding from the Australian Research Council Discovery Project program</span></em></p><p class="fine-print"><em><span>Anna Hopkins and Christina Birnbaum 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>A real-life experiment to mimic future conditions for soils affected by climate change suggests that some of the biggest impacts could be to ecosystems buried out of sight beneath our feet.Anna Hopkins, Lecturer in conservation biology and microbial ecology, Edith Cowan UniversityChristina Birnbaum, Honorary Fellow, Deakin UniversityJoe Fontaine, Lecturer, Environmental Science, Murdoch UniversityNeal Enright, Professor in Plant Ecology, Murdoch UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1039062018-10-11T19:13:13Z2018-10-11T19:13:13ZFarmers’ climate denial begins to wane as reality bites<p>Australia has been <a href="https://www.sciencedirect.com/science/article/pii/S0959378010000130">described</a> as the “front line of the battle for climate change adaptation”, and our farmers are the ones who have to lead the charge. Farmers will have to cope, among other pressures, with <a href="http://www.garnautreview.org.au/">longer droughts, more erratic rainfall, higher temperatures, and changes to the timing of seasons</a>. </p>
<p>Yet, puzzlingly enough to many commentators, climate denial has been widespread among farmers and in the <a href="https://www.smh.com.au/politics/federal/the-biggest-mistake-we-ve-made-on-climate-change-20180529-p4zi3h.html">ranks of the National Party</a>, which purports to represent their interests.</p>
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Read more:
<a href="https://theconversation.com/the-nationals-have-changed-their-leader-but-kept-the-same-climate-story-92348">The Nationals have changed their leader but kept the same climate story</a>
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<p>Back in 2008, <a href="https://agrifutures.infoservices.com.au/items/10-208">only one-third of farmers</a> accepted the science of climate change. Our 2010-11 survey of 946 irrigators in the southern Murray-Darling Basin (<a href="https://www.sciencedirect.com/science/article/pii/S0959378012001392">published in 2013</a>) found similar results: 32% accepted that climate change posed a risk to their region; half disagreed; and 18% did not know. </p>
<p>These numbers have consistently trailed behind the wider public, a clear majority of whom have <a href="https://chrisriedy.me/public-opinion-on-climate-change-in-australia-2d3a4047c4b1">consistently accepted the science</a>. More Australians in 2018 <a href="http://www.tai.org.au/content/climate-nation-2018">accepted the reality of climate change</a> than at almost any time, with 76% accepting climate change is occurring, 11% not believing in it and 13% being unsure. </p>
<p>Yet there are signs we may be on the brink of a wholesale shift in farmers’ attitudes towards climate change. For example, we have seen the creation of <a href="https://www.futurefarmers.com.au/young-carbon-farmers/the-changing-climate">Young Carbon Farmers</a>, <a href="https://www.farmersforclimateaction.org.au/">Farmers for Climate Action</a>, the first ever <a href="https://www.weeklytimesnow.com.au/news/politics/farmers-march-on-parliament-house-to-demand-action-on-climate-change/news-story/5cdfeac5e5a40703406eee594bd42d02">rally on climate change by farmers</a> in Canberra, and <a href="https://www.theguardian.com/environment/2018/sep/16/drought-stricken-farmers-challenge-coalitions-climate-change-stance-in-tv-ad">national adverts</a> by farmers on the need for climate action. Since 2016 the National Farmers Federation has <a href="https://www.afr.com/news/politics/farmers-need-to-do-more-to-tackle-climate-change-says-nff-20180828-h14nme">strengthened its calls</a> for action to reduce greenhouse emissions. </p>
<p>Our latest preliminary research results have also revealed evidence of this change. We surveyed 1,000 irrigators in 2015-16 in the southern Murray-Darling Basin, and found attitudes have shifted significantly since the 2010 survey.</p>
<p>Now, 43% of farmers accept climate change poses a risk to their region, compared with just 32% five years earlier. Those not accepting correspondingly fell to 36%, while the percentage who did not know slightly increased to 21%.</p>
<h2>Why would farmers deny the science?</h2>
<p>There are many factors that <a href="https://www.sciencedirect.com/science/article/pii/S092180091631552X">influence a person’s denial of climate change</a>, with gender, race, education and age all playing a part. While this partly explains the attitudes that persist among farmers (who tend to be predominantly male, older, Caucasian, and have less formal education), it is not the full story. </p>
<p>The very fact that farmers are on the front line of climate change also drives their climate change denial. For a farmer, accepting the science means facing up to the prospect of a harsher, more uncertain future. </p>
<p>Yet as these changes move from future prospect to current reality, they can also have a galvanising effect. Our survey results suggest farmers who have seen their farm’s productivity decrease over time are more likely to accept the science of climate change.</p>
<p>Many farmers who have turned to <a href="https://www.theaustralian.com.au/business/the-deal-magazine/charles-massy-call-of-the-reed-warbler/news-story/f6ad6388aad1bba522341b569b6500a0">regenerative, organic or biodynamic agriculture</a> talk about the change of mindset they went through as they realised they could no longer manage a drying landscape without major changes to their farming practices.</p>
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Read more:
<a href="https://theconversation.com/farmers-experiencing-drought-related-stress-need-targeted-support-98239">Farmers experiencing drought-related stress need targeted support</a>
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<p>In addition, we have found another characteristic that is associated with climate change denial is whether farmers have identified a <a href="https://www.sciencedirect.com/science/article/pii/S0959378012001392">successor</a> for their farm. Many farmers desire to turn their farm over to the next generation, hopefully in a better state than how they received the farm. This is where the psychological aspect of increased future uncertainty plays an <a href="https://www.sciencedirect.com/science/article/pii/S0743016712000484">important role</a> – farmers don’t want to believe their children will face a worse future on the farm. </p>
<p>We all want our children to have better lives than our own, and for farmers in particular, accepting climate change makes that very challenging. But it can also prompt stronger advocacy for doing something about it before it’s too late.</p>
<h2>What can we do?</h2>
<p>Whether farmers do or do not accept climate change, they all have to deal with the uncertainty of weather – and indeed they have been doing so for a very long time. The question is, can we help them to do it better? Given the term “climate change” can be polarising, explicit climate information campaigns will not necessarily deliver the desired results. </p>
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Read more:
<a href="https://theconversation.com/to-help-drought-affected-farmers-we-need-to-support-them-in-good-times-as-well-as-bad-101184">To help drought-affected farmers, we need to support them in good times as well as bad</a>
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<p>What farmers need are policies to help them <a href="https://theconversation.com/drought-is-inevitable-mr-joyce-101444">manage risk and improve their decision-making</a>. This can be done by focusing on how adaptation to weather variability can increase profitability and strengthen the farm’s long-term viability. </p>
<p>Farming policy should be more strategic and forward-thinking; subsidies should be removed for unsustainable practices; and farmers should be rewarded for good land management – both before and during droughts. The quest remains to minimise the pain suffered by all in times of drought.</p><img src="https://counter.theconversation.com/content/103906/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sarah Ann Wheeler currently receives funding from the Australian Research Council, the Australian Centre for International Agricultural Research, SA Department of Environment and Water, and Department of Agriculture and Water Resources. </span></em></p><p class="fine-print"><em><span>Céline Gauges has received funding from the Australian Research Council. </span></em></p>A decade ago, only a third of farmers accepted the science of climate change. But surveys show attitudes have shifted in recent years as the farming community begins to confront what the future holds.Sarah Ann Wheeler, Professor in Water Economics, University of AdelaideCéline Nauges, Research Director, InraeLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/857452017-10-16T18:49:21Z2017-10-16T18:49:21ZTropical thunderstorms are set to grow stronger as the world warms<figure><img src="https://images.theconversation.com/files/190352/original/file-20171016-21986-74bzev.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A supercell thunderstorm in the US state of Oklahoma.</span> <span class="attribution"><span class="source">Hamish Ramsay</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Thunderstorms are set to become more intense throughout the tropics and subtropics this century as a result of climate change, according to <a href="http://www.pnas.org/cgi/doi/10.1073/pnas.1707603114">new research</a>.</p>
<p>Thunderstorms are among nature’s most spectacular phenomena, producing lightning, heavy rainfall, and sometimes awe-inspiring cloud formations. But they also have a range of important impacts on humans and ecosystems.</p>
<p>For instance, lightning produced by thunderstorms is an <a href="http://journals.ametsoc.org/doi/abs/10.1175/1520-0442(1994)007%3C1484:TIOACC%3E2.0.CO;2">important trigger for bushfires globally</a>, while the hailstorm that hit Sydney in April 1999 remains Australia’s <a href="http://www.nationalgeographic.com.au/nature/sydneys-apocalyptic-hailstorm.aspx">costliest ever natural disaster</a>.</p>
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Read more:
<a href="https://theconversation.com/to-understand-how-storms-batter-australia-we-need-a-fresh-deluge-of-data-68487">To understand how storms batter Australia, we need a fresh deluge of data</a>
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<p>Given the damage caused by thunderstorms in Australia and <a href="http://www.independent.co.uk/environment/world-deadliest-storms-tornadoes-cyclones-hail-lightning-bangladesh-india-egypt-zimbabwe-a7741261.html">around the world</a>, it is important to ask whether they will grow in frequency and intensity as the planet warms.</p>
<p>Our main tools for answering such questions are global climate models – mathematical descriptions of the Earth system that attempt to account for the important physical processes governing the climate. But global climate models are not fine-scaled enough to simulate individual thunderstorms, which are typically only a few kilometres across.</p>
<p>But the models can tell us about the ingredients that increase or decrease the power of thunderstorms.</p>
<h2>Brewing up a storm</h2>
<p>Thunderstorms represent the dramatic release of energy stored in the atmosphere. One measure of this stored energy is called “convective available potential energy”, or CAPE. The higher the CAPE, the more energy is available to power updrafts in clouds. Fast updrafts move ice particles in the cold, upper regions of a thunderstorm rapidly upward and downward through the storm. This helps to separate negatively and positively charged particles in the cloud and eventually leads to <a href="http://www.srh.noaa.gov/jetstream/lightning/lightning.html">lightning strikes</a>. </p>
<p>To create thunderstorms that cause damaging wind or hail, often referred to as severe thunderstorms, a second factor is also required. This is called “vertical wind shear”, and it is a measure of the changes in wind speed and direction as you rise through the atmosphere. Vertical wind shear helps to organise thunderstorms so that their updrafts and downdrafts become physically separated. This prevents the downdraft from cutting off the energy source of the thunderstorm, allowing the storm to persist for longer.</p>
<p>By estimating the effect of climate change on these environmental properties, we can estimate the likely effects of climate change on severe thunderstorms.</p>
<h2>Stormy forecast</h2>
<p>My research, carried out with US colleagues and <a href="http://www.pnas.org/cgi/doi/10.1073/pnas.1707603114">published today in Proceedings of the National Academy of Sciences</a>, does just that. We examined changes in the energy available to thunderstorms across the tropics and subtropics in 12 global climate models under a “business as usual” scenario for greenhouse gas emissions. </p>
<p>In every model, days with high values of CAPE grew more frequent, and CAPE values rose in response to global warming. This was the case for almost every region of the tropics and subtropics.</p>
<p>These simulations predict that this century will bring a marked increase in the frequency of conditions that favour severe thunderstorms, unless greenhouse emissions can be significantly reduced.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/190353/original/file-20171016-21953-1j6qu1w.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/190353/original/file-20171016-21953-1j6qu1w.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/190353/original/file-20171016-21953-1j6qu1w.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=320&fit=crop&dpr=1 600w, https://images.theconversation.com/files/190353/original/file-20171016-21953-1j6qu1w.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=320&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/190353/original/file-20171016-21953-1j6qu1w.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=320&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/190353/original/file-20171016-21953-1j6qu1w.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=402&fit=crop&dpr=1 754w, https://images.theconversation.com/files/190353/original/file-20171016-21953-1j6qu1w.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=402&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/190353/original/file-20171016-21953-1j6qu1w.png?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">Change in frequency (in days per year) of favourable conditions for severe thunderstorms for 2081-2100, compared with 1981-2000 averaged across 12 climate models under the RCP8.5 greenhouse-gas concentration scenario. Stippling indicates regions where 11 of the 12 models agree on the sign of the change.</span>
<span class="attribution"><span class="source">CREDIT</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Previous studies have made similar predictions for severe thunderstorms in <a href="http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-13-00426.1">eastern Australia</a> and the <a href="http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-14-00382.1">United States</a>. But ours is the first to study the tropics and subtropics as a whole, a region that is characterised by some of the <a href="http://journals.ametsoc.org/doi/pdf/10.1175/BAMS-87-8-1057">most powerful thunderstorms on Earth</a>.</p>
<h2>What drives the increased energy?</h2>
<p>Different climate models, constructed by <a href="https://www.wcrp-climate.org/wgcm-cmip">different research groups around the world</a>, all agree that global warming will increase the energy available to thunderstorms – a prediction underlined by our new research. But we need to <a href="http://journals.ametsoc.org/doi/abs/10.1175/BAMS-86-11-1609">understand why this happens</a>, so as to be sure that the effect is real and not a product of faulty model assumptions.</p>
<p>My colleagues and I <a href="http://onlinelibrary.wiley.com/doi/10.1002/grl.50796/abstract">previously proposed</a> that high levels of CAPE can develop in the tropics as a result of the turbulent mixing that occurs when clouds draw in air from their surroundings. This mixing prevents the atmosphere from dissipating the available energy too quickly. Instead, the energy builds up for longer and is released in less frequent but more intense storms.</p>
<p>As the climate warms, the amount of water vapour required for cloud formation increases. This is the result of a well-known thermodynamic relationship called the <a href="http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch14/clausius.php">Clausius-Clapeyron relation</a>. In a warmer climate this means the difference in the humidity between the clouds and their surroundings becomes larger. As a result, the mixing mechanism becomes more efficient in building up the available energy. This, we argue, accounts for the increase in CAPE seen in our model simulations.</p>
<p>In our new study, we tested this idea in a global climate model by artificially increasing the strength of the mixing between clouds and their surroundings. As expected, this change produced a large increase in the energy available to thunderstorms in our model.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/australia-faces-a-stormier-future-thanks-to-climate-change-35327">Australia faces a stormier future thanks to climate change</a>
</strong>
</em>
</p>
<hr>
<p>Another prediction of our hypothesis is that days with both high values of CAPE and heavy precipitation tend to occur when the atmosphere is least humid in its middle levels (at altitudes of a few kilometres). Using real data from <a href="http://www.abc.net.au/local/stories/2008/05/09/2240552.htm">weather balloons</a>, we confirmed that this is the case across the tropics and subtropics.</p>
<h2>What this means for future thunderstorms</h2>
<p>The models predict that the energy available for thunderstorms will increase as the Earth warms. But how much more intense will storms actually become as a result?</p>
<p>The answer to that question is currently uncertain, and answering it is the next job for <a href="http://onlinelibrary.wiley.com/doi/10.1002/qj.2567/full">me</a>, and <a href="http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-15-0623.1?journalCode=clim">other researchers around the world</a>.</p>
<p>But it is clear that through our continued greenhouse gas emissions, we are increasing the fuel available to the strongest thunderstorms. Exactly how much stronger our future thunderstorms will ultimately become remains to be seen.</p><img src="https://counter.theconversation.com/content/85745/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Martin Singh receives support from the ARC Centre of Excellence for Climate System Science and has previously been supported by the US National Science Foundation.</span></em></p>The amount of atmospheric energy available to thunderstorms will increase in response to climate change, putting the tropics and subtropics at risk of being lashed with more intense storms.Martin Singh, Lecturer, School of Earth, Atmosphere and Environment, Monash UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/853152017-10-06T05:23:23Z2017-10-06T05:23:23ZThe reality of living with 50°C temperatures in our major cities<figure><img src="https://images.theconversation.com/files/189099/original/file-20171006-9753-1kew8yg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Sydney is facing 50℃ summer days by 2040, new research says.</span> <span class="attribution"><span class="source">Andy/Flickr/Wikimedia Commons</span>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>Australia is hot. But future extreme hot weather will be worse still, with <a href="http://dx.doi.org/10.1002/2017GL074612">new research</a> predicting that Sydney and Melbourne are on course for 50°C summer days by the 2040s if high greenhouse emissions continue. That means that places such as Perth, Adelaide and various regional towns could conceivably hit that mark even sooner.</p>
<p>This trend is worrying, but not particularly surprising given the fact that Australia is setting hot weather records at <a href="http://dx.doi.org/10.1002/2015GL065793">12 times the pace of cold ones</a>. But it does call for an urgent response.</p>
<p>Most of us are used to hot weather, but temperatures of 50°C present unprecedented challenges to our health, work, transport habits, leisure and exercise.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/health-check-how-to-exercise-safely-in-the-heat-37286">Health Check: how to exercise safely in the heat</a>
</strong>
</em>
</p>
<hr>
<p>Humans have an upper limit to heat tolerance, beyond which we suffer <a href="http://www.mdpi.com/1660-4601/12/7/8034">heat stress and even death</a>. Death rates do climb on extremely cold days, but increase much more steeply on extremely hot ones. While cold weather can be tackled with warm clothes, avoiding heat stress requires access to fans or air conditioning, which is not always available.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/189130/original/file-20171006-25792-1icszfu.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/189130/original/file-20171006-25792-1icszfu.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/189130/original/file-20171006-25792-1icszfu.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=358&fit=crop&dpr=1 600w, https://images.theconversation.com/files/189130/original/file-20171006-25792-1icszfu.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=358&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/189130/original/file-20171006-25792-1icszfu.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=358&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/189130/original/file-20171006-25792-1icszfu.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=450&fit=crop&dpr=1 754w, https://images.theconversation.com/files/189130/original/file-20171006-25792-1icszfu.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=450&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/189130/original/file-20171006-25792-1icszfu.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=450&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 death rate in heat ramps up more rapidly than in cold.</span>
<span class="attribution"><span class="source">Data from Li et al., Sci. Rep. (2016); Baccini et al., Epidemiol. (2008); McMichael et al., Int. J. Epidemiol. (2008)</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Even with air conditioning, simply staying indoors is not necessarily an option. People must venture outside to commute and shop. Many essential services have to be done in the open air, such as essential services and maintaining public infrastructure. </p>
<p>Roughly <a href="http://www.mdpi.com/1660-4601/12/7/8034">80% of the energy produced during muscular activity is heat</a>, which must be dissipated to the environment, largely through perspiration. This process is far less effective in hot and humid conditions, and as a result the body’s core temperature begins to climb. </p>
<p>We can cope with increased temperatures for short periods – up to about half an hour – particularly those people who are fit, well hydrated and used to hot conditions. But if body temperature breaches 40-42°C for an extended time, <a href="http://www.mdpi.com/1660-4601/12/7/8034">heat stress and death</a> are likely. In hot enough weather, even going for a walk can be deadly.</p>
<h2>Air conditioning may not save lives</h2>
<p>We expect air conditioning to take the strain, but may not realise just how much strain is involved. Shade temperatures of 50°C mean that direct sunlight can raise the temperature to 60°C or 70°C. Bringing that back to a comfortable 22°C or even a warm 27°C is not always possible and requires a lot of energy – putting serious strain on the electricity grid. </p>
<p>Electricity transmission systems are inherently <a href="http://iopscience.iop.org/article/10.1088/1748-9326/11/11/114008/pdf">vulnerable to extreme heat</a>. This means they can potentially fail simply due to the weather, let alone the increased demand on the grid from power consumers.</p>
<p>Power cuts can cause chaos, including the disruption to traffic signals on roads that may already be made less safe as their surfaces <a href="http://dx.doi.org/10.1038/nclimate3390">soften in the heat</a>. Interruptions to essential services such as power and transport hamper access to lifesaving health care.</p>
<h2>Myopic planning</h2>
<p>It’s a dangerous game to use past extremes as a benchmark when planning for the future. The new research shows that our climate future will be very different from the past. </p>
<p>Melbourne’s 2014 heatwave triggered a surge in demand for ambulances that greatly exceeded the number available. Many of those in distress <a href="http://www.theage.com.au/victoria/anger-over-spike-in-deaths-during-record-victorian-heatwave-20140126-31gxb.html">waited hours for help</a>, and the death toll was <a href="http://mobile.abc.net.au/news/2014-01-23/heatwave-death-toll-expected-to-top-almost-400/5214496">estimated at 203</a>.</p>
<p>Just last month, parts of New South Wales and Victoria experienced temperatures <a href="http://www.bom.gov.au/climate/current/statements/scs62.pdf">16 degrees warmer than the September average</a>, and 2017 is <a href="https://www.ncdc.noaa.gov/sotc/global/201707">tracking as the world’s second-warmest year on record</a>.</p>
<h2>Preparing ourselves</h2>
<p>Last year, the <a href="https://www.climatecouncil.org.au/statement-from-the-australian-summit-on-extreme-heat-and-health">Australian Summit on Extreme Heat and Health</a> warned that the health sector is <a href="https://www.climatecouncil.org.au/uploads/db9b955b4917179139bb594184fc3ae9.pdf">underprepared to face existing heat extremes</a>.</p>
<p>The health sector is concerned about Australia’s slow progress and is responding with the launch of a <a href="http://www.caha.org.au/national-strategy-climate-health-wellbeing">national strategy for climate, health and well-being</a>. Reinstating climate and health research, health workforce training and health promotion are key recommendations. </p>
<p>There is much more to be done, and the prospect of major cities sweltering through 50°C days escalates the urgency. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/climate-policy-needs-a-new-lens-health-and-well-being-62482">Climate policy needs a new lens: health and well-being</a>
</strong>
</em>
</p>
<hr>
<p>Two key messages arise from this. The first is that Australia urgently needs to adapt to the extra warming. Heat-wise communities (or “heat-safe communities” in some states) – where people understand the risks, protect themselves and look after each other – are vital to limit harm from heat exposure. The health sector must have the resources to respond to those who succumb. Research, training and health promotion are central.</p>
<p>The second message is that nations across the world need to <a href="https://theconversation.com/paris-climate-targets-arent-enough-but-we-can-close-the-gap-61798">improve their efforts to reduce greenhouse emissions</a>, so as to meet the <a href="https://theconversation.com/the-paris-climate-agreement-at-a-glance-50465">Paris climate goal</a> of holding global warming to 1.5°C.</p>
<p>If we can do that, we can stave off some of the worst impacts. We have been warned.</p><img src="https://counter.theconversation.com/content/85315/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dr Liz Hanna has received funding from the National Health and Medical Research Council to study health effects of climate change - heat. She is immediate Past President of the Climate and Health Alliance.</span></em></p>Future extreme heat is worse and coming sooner than you might think. Unless we mitigate and adapt we face increasing death rates.Liz Hanna, Honorary Senior Fellow, Australian National UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/775482017-05-15T20:06:56Z2017-05-15T20:06:56ZWhy 2°C of global warming is much worse for Australia than 1.5°C<p>Australia is a land of extremes. We’ve experienced all manner of climate extremes over the past few years, from heatwaves (both on <a href="https://theconversation.com/climate-change-doubled-the-likelihood-of-the-new-south-wales-heatwave-72871">land</a> and over <a href="http://www.abc.net.au/news/2017-03-10/great-barrier-reef-mass-bleaching-event-2017-confirmed/8342174">the Great Barrier Reef</a>), to <a href="https://theconversation.com/drought-conditions-return-to-australias-eastern-states-21149">droughts</a> and <a href="https://theconversation.com/northern-nsw-is-no-stranger-to-floods-but-this-one-was-different-75701">flooding rains</a>.</p>
<p>We can already <a href="https://theconversation.com/unnatural-disasters-how-we-can-spot-climates-role-in-specific-extreme-events-67695">link some of these recent extreme events to climate change</a>. But for others, the link is less clear. </p>
<p>So far we have had <a href="http://globalwarmingindex.org/">about 1°C of global warming</a> above the average pre-industrial climate. So how will extreme weather events change with more warming in the future? Will they become more frequent? Will they become more severe?</p>
<p>We have investigated these questions in our new research, published today in <a href="http://dx.doi.org/10.1038/nclimate3296">Nature Climate Change</a>.</p>
<h2>Climate targets</h2>
<p>The <a href="https://theconversation.com/the-paris-climate-agreement-at-a-glance-50465">Paris Agreement</a>, brokered in 2015, committed the world’s governments to:</p>
<blockquote>
<p>Holding the increase in the global average temperature to well below 2°C above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5°C above pre-industrial levels, recognising that this would significantly reduce the risks and impacts of climate change.</p>
</blockquote>
<p>It is vital that we understand how climate extremes in Australia might change if we limit global warming to either 1.5°C or 2°C, and what the implications might be of pursuing the more lenient target rather than the more ambitious one.</p>
<p>In our study we used state-of-the-art climate model simulations to examine the changing likelihood of different climate extremes under four different scenarios: a natural world without any human-caused climate change; the world of today; a 1.5°C warmer world; and a 2°C warmer one.</p>
<h2>Heat extremes are here to stay</h2>
<p>First, we looked at hot Australian summers, like the record-breaking “angry summer” of 2012-13.</p>
<p>We already knew that <a href="https://theconversation.com/the-human-role-in-our-angry-hot-summer-15596">human influences on the climate had increased the likelihood of hot summers</a>. Our results show that this trend would continue with future warming. In fact, in a world of 2°C global warming, even an average summer would outstrip those historically hot ones like 2012-13.</p>
<p>Australian summer temperatures are strongly related to <a href="https://theconversation.com/explainer-el-nino-and-la-nina-27719">the El Niño-Southern Oscillation</a>, with hot summers more likely to occur during El Niño events, and cooler ones during La Niña episodes. </p>
<p>In the past, a summer as hot as 2012-13 would have been very unlikely during a La Niña. But our modelling predicts that with either 1.5°C or 2°C of global warming, we could expect similarly angry summers to occur during both El Niño and La Niña periods.</p>
<p>We already know that the sea surface temperatures associated with mass bleaching of much of the Great Barrier Reef in early 2016 would have been <a href="https://theconversation.com/great-barrier-reef-bleaching-would-be-almost-impossible-without-climate-change-58408">virtually impossible without climate change</a>. If the world continues to warm to either the 1.5°C or 2°C levels, very warm seas like we saw early last year would become the norm. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/169291/original/file-20170515-3668-kzsdvg.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/169291/original/file-20170515-3668-kzsdvg.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/169291/original/file-20170515-3668-kzsdvg.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=424&fit=crop&dpr=1 600w, https://images.theconversation.com/files/169291/original/file-20170515-3668-kzsdvg.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=424&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/169291/original/file-20170515-3668-kzsdvg.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=424&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/169291/original/file-20170515-3668-kzsdvg.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=533&fit=crop&dpr=1 754w, https://images.theconversation.com/files/169291/original/file-20170515-3668-kzsdvg.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=533&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/169291/original/file-20170515-3668-kzsdvg.png?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"></a>
<figcaption>
<span class="caption">High sea temperatures linked to coral bleaching in Great Barrier Reef will become more likely in a warmer world.</span>
<span class="attribution"><span class="source">Author provided</span></span>
</figcaption>
</figure>
<p>In fact, our research suggests that with 2°C of global warming, the future average sea temperatures around the Great Barrier Reef would be even hotter than the extremes observed around the time of the 2016 bleaching.</p>
<h2>Less change for heavy rains and droughts</h2>
<p>In December 2010 Queensland was devastated by <a href="http://www.abc.net.au/news/2010-12-26/qld-towns-isolated-as-more-rain-looms/1886458">severe flooding following very heavy rainfall</a>. Our analysis suggests that this kind of event is highly unusual, and may well continue to be so. There isn’t a clear signal for an increase or decrease in those events with ongoing climate warming. </p>
<p>Natural climate variability seems to play <a href="https://theconversation.com/the-blame-for-rain-is-mainly-done-in-vain-17896">a greater role</a> than human-driven climate change (at least below the 2°C threshold) when it comes to influencing Australian heavy rainfall events.</p>
<p>The <a href="http://www.bom.gov.au/climate/updates/articles/a010-southern-rainfall-decline.shtml#toc1">Millennium Drought</a> across southeast Australia led to water shortages and crop failures. Drought is primarily driven by a lack of rainfall, but warmer temperatures can exacerbate drought impacts by increasing evaporation. </p>
<p>Our results showed that climate change is increasing the likelihood of hot and dry years like we saw in 2006 across southeast Australia. At 1.5°C and 2°C of global warming these events would probably be more frequent than they are in today’s world.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/169290/original/file-20170515-3672-fqrv3k.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/169290/original/file-20170515-3672-fqrv3k.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/169290/original/file-20170515-3672-fqrv3k.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=449&fit=crop&dpr=1 600w, https://images.theconversation.com/files/169290/original/file-20170515-3672-fqrv3k.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=449&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/169290/original/file-20170515-3672-fqrv3k.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=449&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/169290/original/file-20170515-3672-fqrv3k.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=564&fit=crop&dpr=1 754w, https://images.theconversation.com/files/169290/original/file-20170515-3672-fqrv3k.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=564&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/169290/original/file-20170515-3672-fqrv3k.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=564&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Heat extremes are much more common at 2°C than 1.5°C.</span>
<span class="attribution"><span class="source">Author provided</span></span>
</figcaption>
</figure>
<h2>Not a lost cause</h2>
<p>It is clear that Australia is going to suffer from more frequent and more intense climate extremes as the world warms towards (and very likely <a href="https://theconversation.com/global-warming-could-accelerate-towards-1-5-if-the-pacific-gets-cranky-77175">beyond</a>) the levels described in the Paris Agreement. </p>
<p>If we miss these targets, the warming will continue and the extremes we experience in Australia are going to be even worse.</p>
<p>With either 1.5°C or 2°C global warming, we will see more extremely hot summers across Australia, more frequent marine heatwaves of the kind that can cause bleaching of the Great Barrier Reef, and probably more frequent drought conditions too.</p>
<p>The more warming we experience, the worse the impacts will be. The solution is clear. To limit global warming, the world’s nations need to reduce their greenhouse gas emissions – fast.</p><img src="https://counter.theconversation.com/content/77548/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrew King receives funding from the ARC Centre of Excellence for Climate System Science. </span></em></p><p class="fine-print"><em><span>Ben Henley receives funding from an ARC Linkage Project and is an associate investigator with the ARC Centre of Excellence for Climate System Science.</span></em></p><p class="fine-print"><em><span>David Karoly receives funding from the Australian Research Council Centre of Excellence for Climate System Science and an ARC Linkage grant. He is a member of the Climate Change Authority and the Wentworth Group of Concerned Scientists. </span></em></p>Global warming of 2°C, the higher of the two Paris targets, would see current record-breaking temperatures become the norm in the future, potentially bringing heatwaves to both land and sea.Andrew King, Climate Extremes Research Fellow, The University of MelbourneBen Henley, Research Fellow in Climate and Water Resources, University of Melbourne, The University of MelbourneDavid Karoly, Professor of Atmospheric Science, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/728712017-02-15T19:10:37Z2017-02-15T19:10:37ZClimate change doubled the likelihood of the New South Wales heatwave<figure><img src="https://images.theconversation.com/files/156897/original/image-20170215-19595-al7z5f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Emergency crews tackle a bushfire at Boggabri, one of dozens across NSW during the heatwave.</span> <span class="attribution"><span class="source">AAP/Karen Hodge</span></span></figcaption></figure><p>The heatwave that engulfed southeastern Australia at the end of last week has seen heat records continue to tumble like Jenga blocks.</p>
<p>On Saturday February 11, as New South Wales suffered through the heatwave’s peak, temperatures soared to 47°C in Richmond, 50km northwest of Sydney, while 87 fires raged across the state amid catastrophic fire conditions.</p>
<p>On that day, most of NSW experienced temperatures at least 12°C above normal for this time of year. In White Cliffs, the overnight minimum was 34.2°C, a new record for the state’s <a href="http://www.bom.gov.au/cgi-bin/climate/extremes/annual_extremes.cgi?climtab=tmin_high&area=nsw&year=2017">highest observed minimum temperature</a>. </p>
<p>On Friday, the average maximum temperature right across NSW hit 42.4°C, beating the previous February record of 42.0°C. The new record stood for all of 24 hours before it was smashed again on Saturday, as the whole state averaged 44.0°C at its peak. At this time, NSW was the hottest place on Earth.</p>
<p>A degree or two here or there might not sound like much, but to put it in cricketing parlance, those temperature records are the equivalent of a modern test batsman retiring with an average of over 100 – the feat of outdoing Don Bradman’s fabled 99.94 would undoubtedly be front-page news.</p>
<p>And still the records continue to fall. Mungindi, on the border with Queensland, broke the NSW record of 50 days in a row above 35°C, set just four years ago at Bourke Airport, with the new record now at 52 days.</p>
<p>Meanwhile, two days after that sweltering Saturday we woke to find the fires ignited during the heatwave <a href="http://www.abc.net.au/news/2017-02-13/nsw-fires-wipe-out-dozens-of-homes-with-numbers-expected-to-rise/8264870">still cutting a swathe of destruction</a>, with the small town of Uarbry, east of Dunedoo, <a href="http://www.abc.net.au/news/2017-02-15/nsw-fires-uarbry-couple-mourn-the-loss-of-their-town/8270514">all but burned to the ground</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/156874/original/image-20170215-19591-qp7zvc.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/156874/original/image-20170215-19591-qp7zvc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/156874/original/image-20170215-19591-qp7zvc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=333&fit=crop&dpr=1 600w, https://images.theconversation.com/files/156874/original/image-20170215-19591-qp7zvc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=333&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/156874/original/image-20170215-19591-qp7zvc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=333&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/156874/original/image-20170215-19591-qp7zvc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=419&fit=crop&dpr=1 754w, https://images.theconversation.com/files/156874/original/image-20170215-19591-qp7zvc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=419&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/156874/original/image-20170215-19591-qp7zvc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=419&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Maximum temperature anomalies across NSW on February 11, the peak of the heatwave.</span>
<span class="attribution"><span class="source">Bureau of Meteorology</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>This is all the more noteworthy when we consider that the <a href="https://theconversation.com/el-nino-is-over-but-has-left-its-mark-across-the-world-59823">El Niño of 2015-16 is long gone</a> and the conditions that ordinarily influence our weather are firmly in neutral. This means we should expect average, not sweltering, temperatures.</p>
<p>Since Christmas, much of eastern Australia has been in a flux of extreme temperatures. This increased frequency of heatwaves shows a <a href="https://theconversation.com/weve-learned-a-lot-about-heatwaves-but-were-still-just-warming-up-68174">strong trend in observations</a>, which is set to continue as the human influence on the climate deepens.</p>
<p>It is all part of a rapid warming trend that over the past decade has seen new heat records in Australia outnumber new cold records by <a href="https://theconversation.com/sure-winter-felt-chilly-but-australia-is-setting-new-heat-records-at-12-times-the-rate-of-cold-ones-35607">12 to 1</a>. </p>
<p>Let’s be clear, this is not natural. Climate scientists have long been saying that we would feel the impacts of human-caused climate change in heat records first, before noticing the upward swing in average temperatures (although that is <a href="http://climate.nasa.gov/vital-signs/global-temperature/">happening too</a>). This heatwave is simply the latest example.</p>
<p>What’s more, in just a few decades’ time, summer conditions like these will be <a href="https://theconversation.com/climate-council-heatwaves-are-getting-hotter-and-more-frequent-23253">felt across the whole country regularly</a>.</p>
<h2>Attributing the heat</h2>
<p>The useful thing scientifically about heatwaves is that we can estimate the role that climate change plays in these individual events. This is a relatively new field known as “event attribution”, which has <a href="https://theconversation.com/unnatural-disasters-how-we-can-spot-climates-role-in-specific-extreme-events-67695">grown and improved significantly over the past decade</a>.</p>
<p>Using the <a href="https://theconversation.com/how-your-computer-could-reveal-whats-driving-record-rain-and-heat-in-australia-and-nz-24804">Weather@Home climate model</a>, we looked at the role of human-induced climate change in this latest heatwave, as we have for <a href="https://theconversation.com/its-been-australias-hottest-ever-october-and-thats-no-coincidence-49941">other events before</a>. </p>
<p>We compared the likelihood of such a heatwave in model simulations that factor in human greenhouse gas emissions, compared with simulations in which there is no such human influence. Since 2017 has only just begun, we used model runs representing 2014, which was similarly an El Niño-neutral year, while also experiencing similar levels of human influence on the climate.</p>
<p>Based on this analysis, we found that heatwaves at least as hot as this one are now twice as likely to occur. In the current climate, a heatwave of this severity and extent occurs, on average, once every 120 years, so is still quite rare. However, without human-induced climate change, this heatwave would only occur once every 240 years. </p>
<p>In other words, the waiting time for the recent east Australian heatwave has halved. As climate change worsens in the coming decades, the waiting time will reduce even further.</p>
<p>Our results show very clearly the influence of climate change on this heatwave event. They tell us that what we saw last weekend is a taste of what our future will bring, unless humans can rapidly and deeply cut our greenhouse emissions.</p>
<p>Our increasingly fragile electricity networks will struggle to cope, as the <a href="http://www.news.com.au/technology/environment/residents-told-to-switch-off-appliances-during-crucial-hours-of-peak-demand/news-story/bb2894aec265b29f3c6280e308313c2b">threat of rolling blackouts across NSW</a> showed. It is worth noting that the large number of rooftop solar panels in NSW may have helped to avert such a crisis this time around.</p>
<p>Our hospital emergency departments also feel the added stress of heat waves. When <a href="http://www.smh.com.au/national/death-toll-soared-during-victorias-heatwave-20090406-9ubd.html">an estimated 374 people died</a> from the heatwave that preceded the Black Saturday bushfires the Victorian Institute of Forensic Medicine resorted to <a href="http://www.theage.com.au/victoria/anger-over-spike-in-deaths-during-record-victorian-heatwave-20140126-31gxb.html">storing bodies in hospitals, universities and funeral parlours</a>. The Victorian heatwave of January 2014 saw <a href="http://www.audit.vic.gov.au/publications/20141014-Heatwave-Management/20141014-Heatwave-Management.pdf">167 more deaths than expected</a>, along with significant increases in emergency department presentations and ambulance callouts.</p>
<p>Infrastructure breaks down during heatwaves, as we saw in 2009 when <a href="http://www.abc.net.au/7.30/content/2008/s2477773.htm">railway lines buckled under the extreme conditions</a>, stranding thousands of commuters. It can also strain Australia’s beloved sporting events, as the <a href="http://www.bbc.com/news/world-asia-25743438">2014 Australian Open showed</a>.</p>
<p>These impacts have led state governments and other bodies to investigate heatwave management strategies, while our colleagues at the Bureau of Meteorology have developed a <a href="http://www.bom.gov.au/australia/heatwave/">heatwave forecast service</a> for Australia.</p>
<p>These are likely to be just the beginning of strategies needed to combat heatwaves, with conditions currently regarded as extreme set to be the <a href="https://theconversation.com/2015s-record-breaking-temperatures-will-be-normal-by-2030-its-time-to-adapt-68224">“new normal” by the 2030s</a>. With the ramifications of extreme weather clear to everyone who experienced this heatwave, there is <a href="http://www.abc.net.au/news/2013-10-22/gilding-now-is-the-time-to-talk-about-climate-change/5038006">no better time</a> to talk about how we can ready ourselves.</p>
<p>We urgently need to discuss the health and economic impacts of heatwaves, and how we are going to cope with more of them in the future.</p>
<hr>
<p><em>We would like to acknowledge Robert Smalley, Andrew Watkins and Karl Braganza of the Australian Bureau of Meteorology for providing observations included in this article. This article was amended on February 16, 2017, to include updated weather observations.</em></p><img src="https://counter.theconversation.com/content/72871/count.gif" alt="The Conversation" width="1" height="1" />
<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>Andrew King receives funding from the ARC Centre of Excellence for Climate System Science. </span></em></p><p class="fine-print"><em><span>Matthew Hale receives funding from the Australian Research Council.</span></em></p>Heat records have tumbled across New South Wales as the state suffered through the weekend’s heatwave. A new analysis shows that climate change made this kind of event much less of a rarity.Sarah Perkins-Kirkpatrick, Research Fellow, UNSW SydneyAndrew King, Climate Extremes Research Fellow, The University of MelbourneMatthew Hale, Research Assistant, UNSW SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/693582016-11-25T02:16:47Z2016-11-25T02:16:47ZPlease, Donald Trump, don’t send climate science back to the pre-satellite era<figure><img src="https://images.theconversation.com/files/147498/original/image-20161125-15351-u7ulac.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">You can only truly understand the weather by flying above the clouds.</span> <span class="attribution"><span class="source">NASA</span></span></figcaption></figure><p>Bob Walker, an adviser to US President-elect Donald Trump, has set alarm bells ringing by <a href="https://www.theguardian.com/environment/2016/nov/22/nasa-earth-donald-trump-eliminate-climate-change-research">recommending</a> that NASA’s climate monitoring programs be axed.</p>
<p>But his dismissal of the “politicised science” at NASA’s <a href="https://science.nasa.gov/earth-science">Earth Science Division</a> shows an ignorance of the breadth, role and significance of its <a href="https://theconversation.com/five-reasons-why-cutting-nasas-climate-research-would-be-a-colossal-mistake-69336">contributions to society</a> in the United States and worldwide.</p>
<p>It’s unclear what exactly Walker means by his comment that “future programs should definitely be placed with other agencies”. Is the plan merely to shuffle the deckchairs – same science, different badge — or is it code for cutting the research observation and monitoring efforts altogether? </p>
<p>If the former, it is hard to see what it would achieve, beyond risking a loss of expertise as other agencies attempt to develop the same capabilities as NASA. But the latter is a frightening prospect, because it would effectively take us back to what climate scientists refer to as the “pre-satellite era”. </p>
<p>The global climate system is, well, global. There are places where there is no one around to take measurements, such as the vast expanses of our oceans, the central desert of Australia, and the Arctic and Antarctic regions. But what happens in these remote areas affects the climate elsewhere; the atmosphere has no boundary and the oceans are linked. </p>
<p>Before satellites, the patchiness of weather and climate observations for much of the globe made it hard to detect the patterns that govern rainfall, temperatures and winds. </p>
<p>Now we have a continuous global view of Earth, courtesy of NASA’s Earth observation satellite program. Cutting this research and returning to the pre-satellite era would leave us ignorant not only of Earth’s climate processes, but also of whether or not our environmental policies are effective. </p>
<h2>The value of satellites</h2>
<p>For more than three decades in the early 20th century, the British meteorologist Sir Gilbert T. Walker searched the sparse climate records for patterns that could explain why the Indian monsoon failed in some years. After some laborious number-crunching, he put forward the concept of the “Southern Oscillation”, describing sea-level pressure differences between Darwin and Tahiti in the South Pacific. His <a href="http://www.bom.gov.au/climate/current/soi2.shtml">Southern Oscillation Index</a> is still used today. </p>
<p>When sea-level pressure is lower in Tahiti than Darwin, it causes wind patterns that bring drought to India and northeast Australia, Walker suggested. But the Southern Oscillation was only part of the story. </p>
<p>Almost half a century later, in the late 1960s, early NASA satellite data provided an unprecedented look at the patterns of clouds above the Pacific Ocean. This helped the meteorologist Jacob Bjerknes to link Walker’s sea-level pressure oscillations with other variables such as wind, rainfall (clouds) and ocean temperature variations right across the tropical Pacific. </p>
<p>Crucially, he identified a low-rainfall zone in the central-eastern equatorial Pacific – of which Walker, with his patchy data, had been completely unaware. The “chain reaction” between the atmosphere and ocean now known as the <a href="https://theconversation.com/explainer-el-nino-and-la-nina-27719">El Niño-Southern Oscillation</a> emerged in part from NASA satellite imagery.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/147499/original/image-20161125-15348-dgkwu7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/147499/original/image-20161125-15348-dgkwu7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/147499/original/image-20161125-15348-dgkwu7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/147499/original/image-20161125-15348-dgkwu7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/147499/original/image-20161125-15348-dgkwu7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/147499/original/image-20161125-15348-dgkwu7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/147499/original/image-20161125-15348-dgkwu7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/147499/original/image-20161125-15348-dgkwu7.jpg?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"></a>
<figcaption>
<span class="caption">A visualisation of the strong El Niño that developed in 1997, using NASA sea-surface height data from the TOPEX/Poseidon satellite.</span>
<span class="attribution"><span class="source">NASA</span></span>
</figcaption>
</figure>
<p>Of course, the holy grail when it comes to El Niño is to forecast events ahead of time, because El Niño is a major factor in bringing droughts and floods to countries bordering the Pacific Oceans. This has huge consequences for millions of livelihoods. Australia’s Bureau of Meteorology uses NASA satellite and model data to <a href="http://www.bom.gov.au/climate/enso/">forecast an impending El Niño three to six months ahead of time</a>, while real-time observations help to assess the impacts once the event actually arrives. </p>
<p>This level of forecasting and monitoring was a pipe dream in the pre-satellite era. The same could be said about a host of other global phenomena – from <a href="https://www.nasa.gov/mission_pages/hurricanes/main/index.html">severe storms</a>, to <a href="https://www.nasa.gov/mission_pages/fires/main/index.html">massive wildfires</a>, to <a href="http://aqast.org">air pollution</a>.</p>
<h2>Verifying policy decisions</h2>
<p>If President-elect Trump really needs yet more <a href="http://iopscience.iop.org/article/10.1088/1748-9326/11/4/048002">certainty</a> that human-induced global warming is not a <a href="https://twitter.com/realdonaldtrump/status/265895292191248385?lang=en">hoax</a> and that the recently enacted <a href="http://unfccc.int/paris_agreement/items/9485.php">Paris Agreement</a> will have a meaningful impact, then one of the best ways to achieve this would be to boost NASA’s Earth Science Division.</p>
<p>NASA satellites recently demonstrated the success of US and European environmental regulations in <a href="https://www.nasa.gov/press-release/new-nasa-satellite-maps-show-human-fingerprint-on-global-air-quality">improving air quality over the past decade</a>. NASA has also been central to monitoring the effectiveness of the <a href="http://ozone.unep.org/en/treaties-and-decisions/montreal-protocol-substances-deplete-ozone-layer">Montreal Protocol</a>, the global agreement to safeguard the ozone layer. By keeping a close watch on the <a href="http://ozonewatch.gsfc.nasa.gov">size and extent of the ozone hole</a>, NASA has helped to show that it is <a href="http://ozone.unep.org/Assessment_Panels/SAP/SAP2014_Assessment_for_Decision-Makers.pdf">beginning to recover</a> and that the policy is working.</p>
<h2>Our advice to Trump</h2>
<p>Gilbert T. Walker <a href="http://docs.lib.noaa.gov/rescue/mwr/Suppl/no39-1940.pdf">wrote in 1940</a>: </p>
<blockquote>
<p>I think that the relationships of world weather are so complex that our only chance of explaining them is to accumulate the facts empirically. </p>
</blockquote>
<p>His present-day namesake and Trump adviser Bob Walker also says “<a href="https://www.theguardian.com/environment/2016/nov/22/nasa-earth-donald-trump-eliminate-climate-change-research">we need good science to tell us what the reality is</a>”. One of President-elect Trump’s best chances of achieving this aim is to continue funding scientists to observe Earth from space. </p>
<p>So our advice to Trump is to look beyond the cheap talk about politicisation and appreciate the importance of the work done by NASA’s Earth Science Division. This is not, as Bob Walker asserts, “politically correct environmental monitoring” (whatever that is), but essential data that are already being used to ensure society’s <a href="https://www.youtube.com/watch?v=ag-Zo0izSNg&feature=youtu.be">health and wellbeing</a>. </p>
<p>As for climate change science, the division’s <a href="http://data.giss.nasa.gov/gistemp/">reports on global temperatures</a> are solely based on robust data. What’s being politicised here is not the science but the story that the science tells: that the planet is warming. Let’s not shoot the messenger.</p><img src="https://counter.theconversation.com/content/69358/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Helen McGregor receives funding from the Australian Research Council and the University of Wollongong. McGregor is a member of the Australian Meteorological and Oceanographic Society, the American Geophysical Union and the Australasian Quaternary Association. </span></em></p><p class="fine-print"><em><span>Jenny Fisher receives funding from the Australian Research Council, the Department of the Environment, NASA, and the University of Wollongong. Fisher is a member of the Australian Meteorological and Oceanographic Society and the American Geophysical Union.</span></em></p>Far from being “politicised science”, as a Trump advisor has claimed, NASA’s satellite monitoring has been a crucial help in understanding the planet we live on.Helen McGregor, ARC Future Fellow, University of WollongongJenny Fisher, Lecturer in Atmospheric Chemistry, University of WollongongLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/569422016-04-14T03:24:39Z2016-04-14T03:24:39ZMarine sediments unlock secrets about climate change in South Africa<figure><img src="https://images.theconversation.com/files/118333/original/image-20160412-15861-16u3eog.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Ocean sediments in South Africa provide evidence of climate variation going back 270,000 years.</span> <span class="attribution"><span class="source">Rogan Ward/Reuters</span></span></figcaption></figure><p>Climate change <a href="https://ipcc-wg2.gov/AR5/images/uploads/WGIIAR5-Chap22_FINAL.pdf">projections</a>
suggest that droughts will intensify in most parts of South Africa by the end of the 21st century. This is due to reduced precipitation and the loss of water through the combination of evaporation and plant transpiration. The majority of <a href="http://www.nature.com/nclimate/journal/v5/n9/pdf/nclimate2735.pdf">climate models predict</a> that most southern African countries will warm more than the global mean by 2-3°C. This warming will simulate stronger reductions in precipitation. </p>
<p>But these changes might not happen uniformly across South Africa. The southwestern Cape and Limpopo province seem to be the regions affected most from <a href="http://onlinelibrary.wiley.com/doi/10.1002/joc.1742/full">rainfall reductions</a>. On the other hand, wetter conditions are <a href="http://onlinelibrary.wiley.com/doi/10.1002/joc.1314/abstract">projected</a> in the southeast and along the Drakensberg mountain range.</p>
<p>While seasonal fluctuations in rainfall are normal, rainfall that is substantially below or above average can have serious negative effects. For example, during the 2007 El Niño-related drought in southern Africa, rainfall averaged 50mm-200mm below <a href="http://journals.ametsoc.org/doi/pdf/10.1175/BAMS-89-7-StateoftheClimate">normal</a> rainfall season levels during the most critical period for crops. This caused significant crop damage. </p>
<p><a href="http://onlinelibrary.wiley.com/doi/10.1029/2008GL034180/abstract">Future precipitation projections</a> indicate that both these extremes – droughts as well as flooding – may become more frequent in the future. But do these climate predictions deviate from past natural climate variability? And is the projected change within the range of historical natural variability?</p>
<h2>A silent witness of climate change</h2>
<p>Marine sediments – solid, natural elements that are broken down by processes of weathering and erosion, and collect on the ocean floor – provide evidence of climate variation over time. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/118527/original/image-20160413-23631-62w9lu.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/118527/original/image-20160413-23631-62w9lu.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=464&fit=crop&dpr=1 600w, https://images.theconversation.com/files/118527/original/image-20160413-23631-62w9lu.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=464&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/118527/original/image-20160413-23631-62w9lu.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=464&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/118527/original/image-20160413-23631-62w9lu.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=583&fit=crop&dpr=1 754w, https://images.theconversation.com/files/118527/original/image-20160413-23631-62w9lu.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=583&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/118527/original/image-20160413-23631-62w9lu.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=583&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Studies show that the South African climate changed periodically between long-term droughts and
wet conditions approximately every 23,000 years.</span>
<span class="attribution"><span class="source">Margit Simon</span></span>
</figcaption>
</figure>
<p>These sediment cores offer a journey through time: the longer the sediment core, the longer you are able to go back in time. For example, analysis of sediments delivered into the southwest Indian Ocean from rivers flowing off eastern South Africa can provide evidence of climate variability going back as far as 270,000 years. </p>
<p>Several rivers make their way through KwaZulu-Natal and the Eastern Cape provinces in South Africa before entering the Indian Ocean. During the rainy season they transport more water – and hence more sediment – into the ocean. The composition of the sediment – for example, the amount of iron it carries – also differs between wet and dry periods. In tropical and subtropical humid regions, high precipitation promotes intense chemical weathering of bedrocks. This results in highly weathered soils whose geo-chemical signature, rich in iron, is transferred to marine sediments. </p>
<p>Our <a href="http://www.nature.com/ncomms/journal/v4/n5/full/ncomms2897.html">analysis of marine sediment cores</a> found that South Africa experienced rapid climate transitions toward wetter conditions at times when the Northern Hemisphere experienced extremely cold conditions during the last glacial cycle. These cold phases were associated with slow-downs of the global ocean circulation, which transports warm water from the tropics northwards in the Atlantic Ocean. </p>
<p>Warm tropical and subtropical waters remained longer in the Southern Hemisphere, allowing warm and wet conditions to prevail in South Africa for centuries to thousands of years at a time between 100,000 and 40,000 years ago. The <a href="http://www.sciencedirect.com/science/article/pii/S0012821X13005463">Agulhas Current</a> adjacent to South Africa warmed during that time. This potentially provided heat and moisture for additional rainfall on land. </p>
<p>In addition, our <a href="http://www.nature.com/articles/srep18153">most recent study</a> of a 10m-long sediment archive off the KwaZulu-Natal coast tells the story of climate variation over the past 270,000-odd years. The study, of sediment washed into the Indian Ocean via the Thukela River, reveals that climate changed periodically between long-term droughts and wet conditions approximately every 23,000 years. These cycles were caused by changes in the amount of solar radiation reaching subtropical South Africa. </p>
<p>The reason for this is that every 23,000 years the summer season in southern Africa occurs when the earth is closer to the sun during its orbit. So it receives slightly more solar radiation, warming the land more intensely. This creates changes in winds blowing over the Indian Ocean towards eastern South Africa, bringing more intense rainfall.</p>
<h2>Climate change and human evolution</h2>
<p>There is a striking correspondence between the archaeological record of South Africa and the timing of the abrupt climate change, as derived from <a href="http://www.nature.com/ncomms/journal/v4/n5/full/ncomms2897.html">marine sediments</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/118526/original/image-20160413-23631-13rpn6b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/118526/original/image-20160413-23631-13rpn6b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/118526/original/image-20160413-23631-13rpn6b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=493&fit=crop&dpr=1 600w, https://images.theconversation.com/files/118526/original/image-20160413-23631-13rpn6b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=493&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/118526/original/image-20160413-23631-13rpn6b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=493&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/118526/original/image-20160413-23631-13rpn6b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=619&fit=crop&dpr=1 754w, https://images.theconversation.com/files/118526/original/image-20160413-23631-13rpn6b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=619&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/118526/original/image-20160413-23631-13rpn6b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=619&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Bifacial points recovered from Blombos Cave, South Africa. The Middle Stone Age tools are made of silcrete and finished by pressure flaking.</span>
<span class="attribution"><span class="source">Christopher Henshilwood/University of the Witwatersrand</span></span>
</figcaption>
</figure>
<p>Modern humans, <em>Homo sapiens</em>, first evolved in Africa about 200,000 years ago. South Africa offers an unprecedented variety of archaeological sites that provide compelling evidence for the emergence of modern human behaviour. One example is the use of personal ornaments and the development of complex adaptive strategies during the Middle Stone Age, about 280,000 to 30,000 years ago.</p>
<p>What shaped human cultures during this time is an ongoing debate and the subject of many <a href="https://www.youtube.com/watch?v=Dd_hw4kBPg0">research activities</a>. </p>
<p>Comparing the history of hydrological changes in the region with artefacts from the Middle Stone Age <a href="http://www.nature.com/ncomms/journal/v4/n5/abs/ncomms2897.html">showed</a> a striking correspondence. Climate-driven pulses in southern Africa were probably fundamental to the origin of key elements of modern human behaviour in Africa. But also to the subsequent dispersal of <em>Homo sapiens</em>.</p>
<p>One of the reasons for this is that humans need water, plants need water and so, too, do the animals that humans hunt and eat. These conditions are favourable for population growth. As human population density increases, people are able to network more readily, share ideas and invent technologies. </p>
<p>Looking ahead, many of the projected changes in climate are within the range of historical natural variability. But there are also significant changes that exceed the range of natural climate variability. The main difference between the climate change happening now and that of the geological record is the timing in which these changes occur: climate changes today are occurring at an unprecedented rate.</p><img src="https://counter.theconversation.com/content/56942/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Margit Simon works for Uni Research Climate/Bjerknes Centre for Climate Research, Norway& Cardiff University, UK. She received funding from European Commission 7th Framework Marie Curie People programme FP7/2007-2013 through funding of the Initial Training Network “GATEWAYS” (<a href="http://www.gateways">www.gateways</a> itn.eu) under the grant number 238512, the Climate Change Consortium of Wales. </span></em></p>Marine sediments provide evidence of climate variability in South Africa going back 270,000 years. These changes correspond with changes in the archaeological record of the country.Margit Simon, Postdoctoral Fellow, Uni ResearchLicensed as Creative Commons – attribution, no derivatives.