tag:theconversation.com,2011:/nz/topics/covering-climate-now-75981/articlesCovering Climate Now – The Conversation2020-08-04T19:54:21Ztag:theconversation.com,2011:article/1438212020-08-04T19:54:21Z2020-08-04T19:54:21ZCould electric car batteries feed power back into the grid?<figure><img src="https://images.theconversation.com/files/350824/original/file-20200803-18-pu96m2.jpg?ixlib=rb-1.1.0&rect=94%2C94%2C6884%2C3342&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
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<p><em><strong><a href="https://theconversation.com/nz/topics/climate-explained-74664">Climate Explained</a></strong> is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.</em> </p>
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<p><strong>Why can’t I use the battery from my electric car to export solar power to the grid when I don’t need it?</strong></p>
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<p>Technically it is possible. You could charge your electric vehicle (EV) with solar photovoltaic panels (or any other means), and if the EV is not used, the stored energy could be pushed back into the grid, especially during hours of peak demand for electricity when market prices are high. </p>
<p>This is known as <a href="https://innovationatwork.ieee.org/vehicle-to-grid-v2g-technology/">vehicle-to-grid technology</a> and is seen as the future as we move towards more electrification of transport and a smart grid. </p>
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Read more:
<a href="https://theconversation.com/new-zealand-wants-to-build-a-100-renewable-electricity-grid-but-massive-infrastructure-is-not-the-best-option-143592">New Zealand wants to build a 100% renewable electricity grid, but massive infrastructure is not the best option</a>
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<p>But manufacturers of electric vehicles have been reluctant, at first, to allow the bidirectional flow of power, for <a href="https://reneweconomy.com.au/tesla-explains-evs-selling-electricity-grid-not-good-sounds-47156/">two reasons</a>. </p>
<p>First, it could accelerate the degradation of batteries, which means they would need to be replaced more often. Second, the EV has to connect to the grid in the same way a solar photovoltaic system does, complying with standards to protect line operators and maintenance personnel working on the grid.</p>
<p>Such advanced bidirectional charge controllers come at an additional cost. Nevertheless, EV manufacturers such as Audi and Nissan have now taken steps to enable vehicle-to-grid connection with <a href="https://thedriven.io/2020/07/28/audi-takes-leaf-from-nissan-pursues-vehicle-to-grid-ev-charging/">some of their models</a>. </p>
<p>For EV models that do not have onboard inverters (to convert the DC electricity in the electric car to AC electricity we use in our homes), there are now <a href="https://electrek.co/2020/01/06/wallbox-quasar-tesla-nissan/">bidirectional inverters</a> available to connect any electric car. But the issue of battery life remains.</p>
<p>The continual charging and discharging through a 90% efficient converter shortens the life of the battery, and depending on brand and model, it may need replacing every five years. At more than NZ$5,000, this is a significant price tag for “<a href="https://www.mbie.govt.nz/assets/27e4fc3a4f/prosumer-collectives-a-review-2016.pdf">energy prosumers</a>” – people who both produce and consume energy. </p>
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Read more:
<a href="https://theconversation.com/climate-explained-the-environmental-footprint-of-electric-versus-fossil-cars-124762">Climate explained: the environmental footprint of electric versus fossil cars</a>
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<h2>Economic and practical considerations</h2>
<p>There are other considerations that are very context-specific. These relate to the additional charges for enabling the export of electricity from households, which vary between lines companies and retailers (or local authorities), as well as the buy-back rate of the electricity, which again depends on the purchaser of the electricity. </p>
<p>At the moment, these specific circumstances are seldom favourable to justify the additional cost of the infrastructure needed to connect an electric car to the grid.</p>
<p>There are also practical considerations. If the EV is used for the morning and evening commute, it is not at the home during the day to be charged with a solar system. And if it is (hopefully) not charged during peak demand hours, but mostly in off-peak hours at night, then the vehicle-to-grid route makes less sense. </p>
<p>It only starts to make sense if an EV is not used daily, or if EVs are available to a larger network than just one household. There are major opportunities for EVs to be used in communities with microgrids that manage their own generation and consumption, independent of the larger grid, or if large smart grid operators can manage distributed EVs remotely and more efficiently. </p>
<p>Investigations are ongoing to make this a more <a href="https://www.renewableenergyworld.com/2020/03/02/how-smart-integrated-renewable-energy-systems-can-drive-sustainable-economic-development-in-remote-communities/#gref">practical reality</a> in the near future.</p><img src="https://counter.theconversation.com/content/143821/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alan Brent does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>In the near future, we may see electric cars supplying power to smart grids or communities with their own independent microgrids.Alan Brent, Professor and Chair in Sustainable Energy Systems, Te Herenga Waka — Victoria University of WellingtonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1435262020-07-28T19:57:58Z2020-07-28T19:57:58ZClimate explained: are we doomed if we don’t manage to curb emissions by 2030?<figure><img src="https://images.theconversation.com/files/349778/original/file-20200728-33-1p1j0kq.jpg?ixlib=rb-1.1.0&rect=44%2C134%2C5946%2C3853&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Thongden Studio/Shutterstock</span></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.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">
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<p><em><strong><a href="https://theconversation.com/nz/topics/climate-explained-74664">Climate Explained</a></strong> is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.</em> </p>
<p><em>If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz</em></p>
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<p><strong>Is humanity doomed? If in 2030 we have not reduced emissions in a way that means we stay under say 2°C (I’ve frankly given up on 1.5°C), are we doomed then?</strong></p>
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<p>Humanity is not doomed, not now or even in a worst-case scenario in 2030. But avoiding doom — either the end or widespread collapse of civilisation — is setting a pretty low bar. We can aim much higher than that without shying away from reality.</p>
<p>It’s right to focus on global warming of 1.5°C and 2°C in the first instance. The many manifestations of climate change — including heat waves, droughts, water stress, more intense storms, wildfires, mass extinction and warming oceans — all get progressively worse as the temperature rises. </p>
<p>Climate scientist <a href="https://michaelmann.net/">Michael Mann</a> uses the metaphor of walking into an increasingly dense minefield. </p>
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<h2>Good reasons not to give up just yet</h2>
<p>The <a href="https://www.ipcc.ch/">Intergovernmental Panel on Climate Change</a> described the effects of a 1.5°C increase in average temperatures in a <a href="https://www.ipcc.ch/sr15/">special report</a> last year. They are also nicely summarised in an article about <a href="https://climate.nasa.gov/news/2865/a-degree-of-concern-why-global-temperatures-matter/">why global temperatures matter</a>, produced by NASA. </p>
<p>The global average temperature is currently about <a href="https://climate.nasa.gov/vital-signs/global-temperature/">1.2°C</a> higher than what it was at the time of the Industrial Revolution, some 250 years ago. We are already witnessing localised impacts, including the <a href="https://theconversation.com/we-just-spent-two-weeks-surveying-the-great-barrier-reef-what-we-saw-was-an-utter-tragedy-135197">widespread coral bleaching</a> on Australia’s Great Barrier Reef.</p>
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<img alt="" src="https://images.theconversation.com/files/349752/original/file-20200727-37-126pxpp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/349752/original/file-20200727-37-126pxpp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/349752/original/file-20200727-37-126pxpp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/349752/original/file-20200727-37-126pxpp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/349752/original/file-20200727-37-126pxpp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/349752/original/file-20200727-37-126pxpp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/349752/original/file-20200727-37-126pxpp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">This graph shows different emission pathways and when the world is expected to reach global average temperatures of 1.5°C or 2°C above pre-industrial levels.</span>
<span class="attribution"><span class="source">Global Carbon Project</span>, <span class="license">Author provided</span></span>
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<p>Limiting warming to 1.5°C requires <a href="https://www.unenvironment.org/news-and-stories/press-release/cut-global-emissions-76-percent-every-year-next-decade-meet-15degc">cutting global emissions by 7.6% each year</a> this decade. This does sound difficult, but there are reasons for optimism. </p>
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Read more:
<a href="https://theconversation.com/the-climate-wont-warm-as-much-as-we-feared-but-it-will-warm-more-than-we-hoped-143175">The climate won't warm as much as we feared – but it will warm more than we hoped</a>
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<p>First, it’s possible technically and economically. For example, the use of <a href="https://en.wikipedia.org/wiki/Wind_power">wind</a> and <a href="https://en.wikipedia.org/wiki/Solar_power">solar</a> power has grown exponentially in the past decade, and their prices have plummeted to the point where they are now among the <a href="https://www.irena.org/publications/2020/Jun/Renewable-Power-Costs-in-2019">cheapest</a> sources of electricity. Some areas, including energy storage and industrial processes such as steel and cement manufacture, still need further research and a drop in price (or higher carbon prices).</p>
<p>Second, it’s possible politically. Partly in response to the <a href="https://unfccc.int/process-and-meetings/the-paris-agreement/the-paris-agreement">Paris Agreement</a>, a growing number of countries have adopted stronger targets. <a href="https://www.wri.org/blog/2019/09/what-does-net-zero-emissions-mean-6-common-questions-answered">Twenty countries</a> and regions (including <a href="https://www.mfe.govt.nz/climate-change/zero-carbon-amendment-act">New Zealand</a> and the European Union) are now targeting net zero emissions by 2050 or earlier. </p>
<p>A recent example of striking progress comes from Ireland – a country with a similar emissions profile to New Zealand. The incoming coalition’s “<a href="https://www.irishtimes.com/news/ireland/irish-news/programme-for-government-what-are-the-main-points-in-the-five-year-plan-1.4279046">programme for government</a>” includes emission cuts of 7% per year and a reduction by half by 2030. </p>
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Read more:
<a href="https://theconversation.com/young-people-wont-accept-inaction-on-climate-change-and-theyll-be-voting-in-droves-116361">Young people won't accept inaction on climate change, and they'll be voting in droves</a>
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<p>Third, it’s possible socially. Since 2019, we have seen the massive growth of the <a href="https://theconversation.com/climate-change-children-are-carving-out-a-place-in-politics-now-adults-must-listen-and-act-123704">School Strike 4 Climate</a> movement and an increase in fossil fuel <a href="https://gofossilfree.org/divestment/commitments/">divestment</a>. Several media organisations, including The Conversation, have made a <a href="https://theconversation.com/media-impartiality-on-climate-change-is-ethically-misguided-and-downright-dangerous-130778">commitment to evidence-based coverage of climate change</a> and calls for a <a href="https://www.nytimes.com/2019/02/21/climate/green-new-deal-questions-answers.html">Green New Deal</a> are coming from a range of political parties, especially in the US and Europe.</p>
<p>There is also a growing understanding that to ensure a safe future we need to consume less overall. If these trends continue, then I believe we can still stay below 1.5°C.</p>
<h2>The pessimist perspective</h2>
<p>Now suppose we don’t manage that. It’s 2030 and emissions have only fallen a little bit. We’re staring at 2°C in the second half of the century. </p>
<p>At 2°C of warming, we could expect to lose more than 90% of our coral reefs. Insects and plants would be at higher risk of extinction, and the number of dangerously hot days would increase rapidly. </p>
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Read more:
<a href="https://theconversation.com/not-convinced-on-the-need-for-urgent-climate-action-heres-what-happens-to-our-planet-between-1-5-c-and-2-c-of-global-warming-123817">Not convinced on the need for urgent climate action? Here's what happens to our planet between 1.5°C and 2°C of global warming</a>
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<p>The challenges would be exacerbated and we would have new issues to consider. First, under the “<a href="https://news.mongabay.com/2009/06/proving-the-shifting-baselines-theory-how-humans-consistently-misperceive-nature/">shifting baseline</a>” phenomenon — essentially a failure to notice slow change and to value what is already lost — people might discount the damage already done. Continuously worsening conditions might become the new normal. </p>
<p>Second, climate impacts such as mass migration could lead to a rise of nationalism and make international cooperation harder. And third, we could begin to pass unpredictable “<a href="https://www.nature.com/articles/d41586-019-03595-0">tipping points</a>” in the Earth system. For example, warming of more than 2°C could set off widespread melting in Antarctica, which in turn would contribute to sea level rise.</p>
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Read more:
<a href="https://theconversation.com/if-warming-exceeds-2-c-antarcticas-melting-ice-sheets-could-raise-seas-20-metres-in-coming-centuries-124484">If warming exceeds 2°C, Antarctica's melting ice sheets could raise seas 20 metres in coming centuries</a>
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<p>But true doom-mongers tend to assume a worst-case scenario on virtually every area of uncertainty. It is important to remember that such scenarios are not very likely.</p>
<p>While bad, this 2030 scenario doesn’t add up to doom — and it certainly doesn’t change the need to move away from fossil fuels to low-carbon options.</p><img src="https://counter.theconversation.com/content/143526/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Robert McLachlan does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>To limit warming to 1.5°C above pre-industrial levels, we’ll need to cut global emissions by 7.6% each year this decade. It’s difficult, but not impossible.Robert McLachlan, Professor in Applied Mathematics, Massey UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1417842020-07-07T19:52:07Z2020-07-07T19:52:07ZClimate explained: what the world was like the last time carbon dioxide levels were at 400ppm<figure><img src="https://images.theconversation.com/files/345916/original/file-20200706-3943-1sq2bv1.jpg?ixlib=rb-1.1.0&rect=33%2C92%2C5573%2C3640&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Gil.K/Shutterstock</span></span></figcaption></figure><figure class="align-left ">
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<p><em><strong><a href="https://theconversation.com/nz/topics/climate-explained-74664">Climate Explained</a></strong> is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.</em> </p>
<p><em>If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz</em></p>
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<p><strong>What was the climate and sea level like at times in Earth’s history when carbon dioxide in the atmosphere was at 400ppm?</strong></p>
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<p>The last time global carbon dioxide levels were consistently at or above 400 parts per million (ppm) was around <a href="https://www.nature.com/articles/nature14145">four million years ago</a> during a geological period known as the <a href="http://www.geologypage.com/2014/05/pliocene-epoch.html">Pliocene Era</a> (between 5.3 million and 2.6 million years ago). The world was about 3°C warmer and sea levels were higher than today. </p>
<p>We know how much carbon dioxide the atmosphere contained in the past by studying ice cores from Greenland and Antarctica. As compacted snow gradually changes to ice, it traps air in bubbles that contain <a href="https://www.cambridge.org/core/journals/annals-of-glaciology/article/enclosure-of-air-during-metamorphosis-of-dry-firn-to-ice/09D9C60A8DA412D16645E6E6ABC1892F">samples of the atmosphere at the time</a>. We can sample ice cores to reconstruct past concentrations of carbon dioxide, but this record only takes us back about a million years.</p>
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Read more:
<a href="https://theconversation.com/climate-explained-what-caused-major-climate-change-in-the-past-137874">Climate explained: what caused major climate change in the past?</a>
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<p>Beyond a million years, we don’t have any direct measurements of the composition of ancient atmospheres, but we can use several methods to estimate past levels of carbon dioxide. One method uses the relationship between plant pores, known as stomata, that regulate gas exchange in and out of the plant. The density of these stomata is <a href="https://journals.sagepub.com/doi/abs/10.1177/095968369200200109">related to atmospheric carbon dioxide</a>, and fossil plants are a good indicator of concentrations in the past.</p>
<p>Another technique is to examine sediment cores from the ocean floor. The sediments build up year after year as the bodies and shells of dead plankton and other organisms rain down on the seafloor. We can use isotopes (chemically identical atoms that differ only in atomic weight) of boron taken from the shells of the dead plankton to reconstruct changes in the acidity of seawater. From this we can work out the level of carbon dioxide in the ocean. </p>
<p>The data from four-million-year-old sediments suggest that <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2010PA002055">carbon dioxide was at 400ppm back then</a>.</p>
<h2>Sea levels and changes in Antarctica</h2>
<p>During colder periods in Earth’s history, ice caps and glaciers grow and sea levels drop. In the recent geological past, during the most recent ice age about 20,000 years ago, sea levels were at least <a href="https://science.sciencemag.org/content/292/5517/679.abstract">120 metres lower</a> than they are today.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/345976/original/file-20200707-26-1nsf11x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/345976/original/file-20200707-26-1nsf11x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/345976/original/file-20200707-26-1nsf11x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/345976/original/file-20200707-26-1nsf11x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/345976/original/file-20200707-26-1nsf11x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/345976/original/file-20200707-26-1nsf11x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/345976/original/file-20200707-26-1nsf11x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Recent research shows that west Antarctica is now melting.</span>
<span class="attribution"><span class="source">Elaine Hood/NSF</span></span>
</figcaption>
</figure>
<p>Sea-level changes are calculated from changes in isotopes of oxygen in the shells of marine organisms. For the Pliocene Era, <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2004PA001071">research</a> shows the sea-level change between cooler and warmer periods was around 30-40 metres and sea level was higher than today. Also during the Pliocene, we know the West Antarctic Ice Sheet was <a href="https://www.nature.com/articles/nature07867">significantly smaller</a> and global average temperatures were about 3°C warmer than today. Summer temperatures in high northern latitudes were up to 14°C warmer. </p>
<p>This may seem like a lot but modern observations show strong <a href="https://journals.ametsoc.org/jcli/article/23/14/3888/32547">polar amplification</a> of warming: a 1°C increase at the equator may raise temperatures at the poles by 6-7°C. It is one of the reasons why Arctic sea ice is disappearing. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/climate-explained-why-carbon-dioxide-has-such-outsized-influence-on-earths-climate-123064">Climate explained: why carbon dioxide has such outsized influence on Earth's climate</a>
</strong>
</em>
</p>
<hr>
<h2>Impacts in New Zealand and Australasia</h2>
<p>In the Australasian region, there was no Great Barrier Reef, but there may have been <a href="https://link.springer.com/content/pdf/10.1007/BF02537376.pdf">smaller reefs along the northeast coast of Australia</a>. For New Zealand, the partial melting of the West Antarctic Ice Sheet is probably the most critical point. </p>
<p>One of the key features of New Zealand’s current climate is that Antarctica is cut off from global circulation during the winter because of the big <a href="https://www.tandfonline.com/doi/abs/10.3402/tellusa.v54i5.12161">temperature contrast</a> between Antarctica and the Southern Ocean. When it comes back into circulation in springtime, New Zealand gets strong storms. Stormier winters and significantly warmer summers were likely in the mid-Pliocene because of a weaker polar vortex and a warmer Antarctica.</p>
<p>It will take more than a few years or decades of carbon dioxide concentrations at 400ppm to trigger a significant shrinking of the West Antarctic Ice Sheet. But recent studies show that <a href="http://nora.nerc.ac.uk/id/eprint/521027/">West Antarctica is already melting</a>. </p>
<p>Sea-level rise from a partial melting of West Antarctica could easily exceed a metre or more by 2100. In fact, if the whole of the West Antarctic melted it could <a href="http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.695.7239&rep=rep1&type=pdf">raise sea levels by about 3.5 metres</a>. Even smaller increases raise the risk of <a href="https://www.pce.parliament.nz/publications/preparing-new-zealand-for-rising-seas-certainty-and-uncertainty">flooding in low-lying cities</a> including Auckland, Christchurch and Wellington.</p><img src="https://counter.theconversation.com/content/141784/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>James Shulmeister receives funding from the Australian Research Council and is part of a National Science Foundation grant from the US. As well as being Professor and Head of School at the University of Canterbury in New Zealand, he is an Adjunct Professor at the University of Queensland, Australia and an associate investigator at the ARC Centre of Excellence for Australian Biodiversity and Heritage (CABAH)</span></em></p>The last time global carbon dioxide levels were around 400ppm was four million years ago. On average, the world was 3°C warmer, but in high northern latitudes, it was up to 14°C warmer than today.James Shulmeister, Professor, University of CanterburyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1416042020-06-30T19:11:28Z2020-06-30T19:11:28ZClimate explained: will the COVID-19 lockdown slow the effects of climate change?<figure><img src="https://images.theconversation.com/files/344674/original/file-20200629-155345-814348.jpg?ixlib=rb-1.1.0&rect=39%2C239%2C2623%2C1756&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">ChameleonsEye/Shutterstock</span></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.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">
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<span class="attribution"><a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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<p><em><strong><a href="https://theconversation.com/nz/topics/climate-explained-74664">Climate Explained</a></strong> is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.</em> </p>
<p><em>If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz</em></p>
<hr>
<blockquote>
<p><strong>Do you think the COVID-19 pandemic lockdown will slow or possibly reverse the effects of climate change (due to decreased air travel, cars, fossil fuels being emitted)?</strong></p>
</blockquote>
<p>The COVID-19 lockdown has affected the environment in a number of ways. </p>
<p>The first is a <a href="https://edition.cnn.com/2020/04/09/politics/airline-passengers-decline/index.html">reduction in air travel</a> and associated emissions. Globally, <a href="https://www.ipcc.ch/site/assets/uploads/2018/02/ipcc_wg3_ar5_chapter8.pdf">air travel accounts for around 12%</a> of the transport sector’s greenhouse gas emissions and this was predicted to rise. An ongoing reduction in air travel would lead to lower greenhouse gas emissions.</p>
<p>The lockdown has also meant less travel by road, which has resulted in measurably lower vehicle emissions and <a href="https://www.newshub.co.nz/home/new-zealand/2020/05/coronavirus-seven-weeks-in-lockdown-causes-air-pollution-to-drop-75-percent-across-auckland-wellington-and-christchurch.html">cleaner air</a> in New Zealand. </p>
<p>Worldwide, daily emissions of carbon dioxide had <a href="https://www.nature.com/articles/s41558-020-0797-x">dropped by 17% by early April</a> (compared with 2019 levels) and just under half of the reduction came from changes in land transport. The same study estimated the pandemic could reduce global emissions by between 4% (if the world returns to pre-pandemic conditions mid-year) and 7% (if restrictions remain in place until the end of 2020). </p>
<p>But even a 7% drop would mean emissions for 2020 will <a href="https://www.cbc.ca/news/technology/pandemic-climate-change-covid-emissions-1.5579232">roughly be the same as in 2011</a>. The long-term impact of the pandemic on climate change depends on the actions governments take as economies recover – they will influence the path of global carbon dioxide emissions for decades.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/coronavirus-is-a-sliding-doors-moment-what-we-do-now-could-change-earths-trajectory-137838">Coronavirus is a 'sliding doors' moment. What we do now could change Earth's trajectory</a>
</strong>
</em>
</p>
<hr>
<h2>Choosing how you travel</h2>
<p>In New Zealand, the biggest reduction in emissions came from people not travelling as much, or at all. But as the lockdown lifted, these <a href="https://niwa.co.nz/atmosphere/air-quality-updates-during-covid19-level-restrictions/air-quality-update-8-end-of-level-3-restrictions">improvements seemed to be short term</a>, with traffic volumes and the associated pollution now <a href="https://www.stuff.co.nz/environment/climate-news/121361914/coronavirus-auckland-traffic-pollution-soars-under-covid19-alert-level-3">back at pre-COVID-19 levels</a>.</p>
<p>There is significant uncertainty about all of the changes prompted by the pandemic lockdown, but international air travel is predicted to remain down in the short to medium term as the risk of inter-country transfer of COVID-19 remains high. For how long depends on the ability of other countries to effectively manage the virus or the availability of a vaccine. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-changes-brought-on-by-coronavirus-could-help-tackle-climate-change-133509">How changes brought on by coronavirus could help tackle climate change</a>
</strong>
</em>
</p>
<hr>
<p>Land transport is more within our control in New Zealand. How, and how much, we choose to travel will determine our greenhouse gas emissions. While many people are returning to their cars, there are some lockdown changes that could lead to longer-term emissions reductions. </p>
<p>Firstly, people now realise it is <a href="https://www.stuff.co.nz/environment/climate-news/121361914/coronavirus-auckland-traffic-pollution-soars-under-covid19-alert-level-3">possible to work from home</a> and may want to continue doing so in the future. </p>
<p>Secondly, there is <a href="https://at.govt.nz/about-us/news-events/covid-19-more-families-using-local-cycleways-during-lockdown/">evidence some people</a> <a href="https://www.rnz.co.nz/news/national/415435/cycling-popularity-changes-gear-during-lockdown-and-supporters-look-to-capitalise">walked and cycled more</a> than they had done before during lockdown. Retailers are reporting <a href="https://www.tvnz.co.nz/one-news/new-zealand/bike-retailers-warning-shortages-after-covid-19-lockdown-sees-interest-spike">increased demand for bicycles</a>. </p>
<h2>Keeping some lockdown changes</h2>
<p>In many parts of the world, governments are implementing plans to lock in some of the reductions in traffic caused by the pandemic. </p>
<p>This includes allocating road space <a href="https://www.theguardian.com/world/2020/apr/21/milan-seeks-to-prevent-post-crisis-return-of-traffic-pollution">to walking and cycling</a> and incentives for people to buy or maintain bikes (such as in <a href="https://www.bbc.com/news/world-europe-52483684">France</a> and the <a href="https://www.forbes.com/sites/carltonreid/2020/06/23/uk-government-rolls-out-50-fix-your-bike-voucher-scheme-one-month-after-first-announcing-it/#21db04435448">UK</a>). </p>
<p>There are also initiatives to decarbonise the car fleet by replacing fossil fuelled vehicles with <a href="https://www.iea.org/commentaries/as-the-covid-19-crisis-hammers-the-auto-industry-electric-cars-remain-a-bright-spot">electric ones</a>. In New Zealand, electric vehicles are <a href="https://www.transport.govt.nz/land/road-user-charges-ruc-and-petrol-excise-duty-ped/roaduserchargeslegislationchanges/vehiclesexemptfrompayingrucqandas/">exempt from road user charges</a> and the government is investigating ways to increase the uptake of <a href="https://www.transport.govt.nz/news/land/green-freight-2020-strategic-working-paper/">alternative fuels in the road freight industry</a>. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/new-zealands-covid-19-budget-delivers-on-one-crisis-but-largely-leaves-climate-change-for-another-day-138524">New Zealand's COVID-19 budget delivers on one crisis, but largely leaves climate change for another day</a>
</strong>
</em>
</p>
<hr>
<p>These measures are important and reduce greenhouse gas emissions, but they are not designed to reduce the number of people travelling, or the mode they use. Congestion is an ongoing issue in Auckland and is now estimated to cost more than <a href="https://nzier.org.nz/static/media/filer_public/6f/df/6fdfdada-923e-4199-8da9-cc940ae25bc1/nzier_report_on_auckland_benefits_of_decongestion.pdf">NZ$1 billion per year</a>. </p>
<p>Another challenge is the growing rate of obesity, with <a href="https://www.health.govt.nz/nz-health-statistics/health-statistics-and-data-sets/obesity-statistics">one in three New Zealanders</a> now obese. This is at least partly a transport-related challenge. We know <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2937005/">obesity rates are higher</a> in places where more people travel by car. Increased use of public transport can reduce obesity – as well as <a href="https://www.zmescience.com/medicine/public-transportation-vs-obesity/">making people happier</a>. </p>
<p>How long-lasting the COVID-19 impact on emissions is depends on how much we want some of the temporary changes to continue. For example, COVID-19 showed more people walk and cycle if there are fewer cars, which supports evidence that safety is a big barrier to cycling and we need dedicated cycle ways to <a href="https://www.zmescience.com/medicine/public-transportation-vs-obesity/">keep people away from traffic</a>. We also know people are happy with a little inconvenience to have safer <a href="https://www.sciencedirect.com/science/article/pii/S2214140520300761?via%3Dihub">play-friendly streets</a>. </p>
<p>Encouraging some of the lockdown behavioural changes could have additional benefits and reduce greenhouse gas emissions at the same time.</p><img src="https://counter.theconversation.com/content/141604/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Simon Kingham receives research funding from MBIE and the Ministry of Health.
He is seconded two days a week to the Ministry of Transport as their Chief Science Advisor </span></em></p>The drop in traffic during COVID-19 lockdowns reduced global emissions. If we keep encouraging cycling and working from home beyond the pandemic, our climate goals may become more achievable.Simon Kingham, Professor, University of CanterburyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1411942020-06-23T20:16:44Z2020-06-23T20:16:44ZClimate Explained: what Earth would be like if we hadn’t pumped greenhouse gases into the atmosphere<figure><img src="https://images.theconversation.com/files/343101/original/file-20200622-75483-xbfslh.jpg?ixlib=rb-1.1.0&rect=765%2C100%2C5954%2C2458&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">OSORIOartist/Shutterstock</span></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.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">
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<p><em><strong><a href="https://theconversation.com/nz/topics/climate-explained-74664">Climate Explained</a></strong> is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.</em> </p>
<p><em>If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz</em></p>
<p><em><strong>This week, Climate Explained answers two similar questions.</strong></em></p>
<blockquote>
<p><strong>If humans had not contributed to greenhouses gases in any way at all, what would the global temperature be today, compared to the 1800s before industrialisation?</strong></p>
</blockquote>
<p>and</p>
<blockquote>
<p><strong>My question is what happens when all the greenhouse gases are eliminated? What keeps the planet from cooling past a point that is good?</strong></p>
</blockquote>
<p>Earth’s atmosphere is a remarkably thin layer of gases that sustain life. </p>
<p>The diameter of Earth is 12,742km and the atmosphere is about 100km thick. If you took a model globe and wrapped it up, a single sheet of tissue paper would represent the thickness of the atmosphere.</p>
<p>The gases that make up Earth’s atmosphere are mostly nitrogen and oxygen, and small quantities of trace gases such as argon, neon, helium, the <a href="https://ozonewatch.gsfc.nasa.gov/facts/SH.html">protective ozone layer</a> and various greenhouse gases – so named because they trap heat emitted by Earth. </p>
<p>The most abundant greenhouse gas in Earth’s atmosphere is water vapour - and it is this gas that provides the natural greenhouse effect. Without this and the naturally occurring quantities of other greenhouse gases, Earth would be <a href="https://niwa.co.nz/our-science/climate/information-and-resources/clivar/greenhouse">about 33°C colder</a> and uninhabitable to life as we know it.</p>
<h2>Changing Earth’s atmosphere</h2>
<p>Since pre-industrial times, human activities have led to the accumulation of greenhouse gases such as carbon dioxide, methane and nitrous oxide in the atmosphere. The concentration of <a href="https://scrippsco2.ucsd.edu/">atmospheric carbon dioxide has risen</a> from about 280 parts per million (ppm) before the <a href="https://en.wikipedia.org/wiki/Industrial_Revolution">first industrial revolution</a> some 250 years ago, to a <a href="https://www.washingtonpost.com/weather/2020/06/04/carbon-dioxide-record-2020/">new high since records began</a> of just over 417ppm. As a result of continued increases, the global average temperature has climbed by just over <a href="https://earthobservatory.nasa.gov/world-of-change/global-temperatures">1°C since pre-industrial times</a>.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/climate-explained-why-carbon-dioxide-has-such-outsized-influence-on-earths-climate-123064">Climate explained: why carbon dioxide has such outsized influence on Earth's climate</a>
</strong>
</em>
</p>
<hr>
<p>While these long-lived greenhouse gases have raised Earth’s average surface temperature, human activities have altered atmospheric composition in other ways as well. Particulate matter in the atmosphere, such as soot and dust, can cause <a href="https://www.who.int/gho/phe/outdoor_air_pollution/burden_text/en/">health problems</a> and degrades air quality in many industrialised and urban regions. </p>
<p>Particulate matter can <a href="https://www.ipcc.ch/site/assets/uploads/2018/02/WG1AR5_Chapter08_FINAL.pdf">partially offset greenhouse gas warming</a>, but its climate effects depend on its composition and <a href="https://www.nature.com/articles/s41467-018-05838-6">geographical distribution</a>. Climate in the southern hemisphere has also been affected by chlorofluorocarbons (CFCs), which led to the development of the <a href="https://www.scientificamerican.com/article/shrinking-ozone-hole-climate-change-are-causing-atmospheric-tug-of-war/">Antarctic ozone hole</a>. </p>
<p>If people had not altered the composition of the atmosphere at all through emitting greenhouse gases, particulate matter and ozone-destroying CFCs, we would expect the global average temperature today to be similar to the pre-industrial period – although some short-term variation associated with the Sun, <a href="https://earthdata.nasa.gov/learn/sensing-our-planet/volcanoes-and-climate-change">volcanic eruptions</a> and internal variability would still have occurred. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/what-is-a-pre-industrial-climate-and-why-does-it-matter-78601">What is a pre-industrial climate and why does it matter?</a>
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</em>
</p>
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<p>In a world that is about 1°C warmer than during pre-industrial times, New Zealand is already facing the environmental and <a href="https://www.newsroom.co.nz/2020/06/17/1233114/nzs-climate-change-toll-tops-800m-from-just-two-droughts">economic costs</a> associated with climate change. The former head of the UN Framework Convention on Climate Change (<a href="https://unfccc.int/process-and-meetings/the-convention/what-is-the-united-nations-framework-convention-on-climate-change">UNFCCC</a>), Christiana Figueres, <a href="https://www.rnz.co.nz/programmes/post-covid-podcast/story/2018748032/after-the-virus-the-environment">argues</a> that with trillions of dollars being spent around the world in economic stimulus packages following the COVID-19 pandemic, we need strong commitments to a low-carbon future if the world is to limit warming to 1.5°C above pre-industrial levels. </p>
<h2>What needs to happen</h2>
<p>Greenhouse gases have long lifetimes – about a decade for methane and hundreds to thousands of years for carbon dioxide. We will need to reduce emissions aggressively over a sustained period, until their abundance in the atmosphere starts to decline. </p>
<p>When New Zealand entered the Level 4 coronavirus lockdown in March 2020, almost two weeks passed (the incubation period of the virus) before the number of new cases started to decline. Waiting for atmospheric carbon dioxide concentrations to decrease, even while we reduce emissions, will be similar, except we’ll be <a href="https://scripps.ucsd.edu/programs/keelingcurve/2020/03/11/what-does-it-take-for-the-coronavirus-or-other-major-economic-events-to-affect-global-carbon-dioxide-readings/">waiting for decades</a>. </p>
<p>It is very unlikely that we could ever reduce greenhouse gas concentrations to the point that it becomes dangerous for life as we know it. Doing so would involve overcoming the natural greenhouse effect.</p>
<p>Recent <a href="https://www.nature.com/articles/s41558-018-0091-3?proof=trueIn">research</a> into greenhouse gas emission scenarios provides guidance on what will need to happen to stabilise Earth’s temperature at 1.5°C above pre-industrial levels. A rapid transition away from fossil fuels toward low-carbon energy is imperative; some form of carbon dioxide capture to remove it from the atmosphere may also be necessary. </p>
<p>Short-term and scattered climate policy will not be sufficient to support the transitions we need, and achieving 1.5°C will not be possible as long as global inequalities remain high.</p><img src="https://counter.theconversation.com/content/141194/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Laura Revell receives funding from the Ministry of Business, Innovation and Employment, the Deep South National Science Challenge and the Royal Society of New Zealand Marsden fund.</span></em></p>If we had not altered the composition of the atmosphere at all through emitting greenhouse gases, particulate matter and ozone-destroying chemicals, the average temperature would have remained stable.Laura Revell, Senior Lecturer in Environmental Physics, University of CanterburyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1402462020-06-09T19:54:05Z2020-06-09T19:54:05ZClimate explained: does your driving speed make any difference to your car’s emissions?<figure><img src="https://images.theconversation.com/files/340440/original/file-20200608-176538-15lwe35.jpg?ixlib=rb-1.1.0&rect=49%2C149%2C4695%2C3009&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">SP Photo/Shutterstock</span></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.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">
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<span class="attribution"><a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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<p><em><strong><a href="https://theconversation.com/nz/topics/climate-explained-74664">Climate Explained</a></strong> is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.</em> </p>
<p><em>If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz</em></p>
<blockquote>
<p><strong>Does reducing speed reduce emissions from the average car?</strong> </p>
</blockquote>
<p>Every car has an optimal speed range that results in minimum fuel consumption, but this range differs between vehicle types, design and age.</p>
<p>Typically it looks like this graph below: fuel consumption rises from about 80km/h, partly because air resistance increases.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/340495/original/file-20200609-165349-1dwyw4r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/340495/original/file-20200609-165349-1dwyw4r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/340495/original/file-20200609-165349-1dwyw4r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/340495/original/file-20200609-165349-1dwyw4r.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/340495/original/file-20200609-165349-1dwyw4r.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/340495/original/file-20200609-165349-1dwyw4r.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/340495/original/file-20200609-165349-1dwyw4r.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><span class="license">Author provided</span></span>
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</figure>
<p>But speed is only one factor. No matter what car you are driving, you can reduce fuel consumption (and therefore emissions) by driving more smoothly. </p>
<p>This includes anticipating corners and avoiding sudden braking, taking the foot off the accelerator just before reaching the peak of a hill and cruising over it, and removing roof racks or bull bars and heavier items from inside when they are not needed to make the car lighter and more streamlined. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/climate-explained-the-environmental-footprint-of-electric-versus-fossil-cars-124762">Climate explained: the environmental footprint of electric versus fossil cars</a>
</strong>
</em>
</p>
<hr>
<h2>Driving wisely</h2>
<p>In New Zealand, <a href="https://www.aa.co.nz/about/newsroom/media-releases/events/aa-energywise-rally-starts-with-a-rush/">EnergyWise rallies</a> used to be run over a 1200km course around the North Island. They were designed to demonstrate how much fuel could be saved through good driving habits. </p>
<p>The competing drivers had to reach each destination within a certain time period. Cruising too slowly at 60-70km/h on straight roads in a 100km/h zone just to save fuel was not an option (also because driving too slowly on open roads can contribute to accidents). </p>
<p>The optimum average speed (for both professional and average drivers) was typically around 80km/h. The key to saving fuel was driving smoothly. </p>
<p>In the first rally in 2002, the Massey University entry was a brand new diesel-fuelled Volkswagen Golf (kindly loaned by VW NZ), running on 100% biodiesel made from waste animal fat (as Z Energy has been <a href="https://www.newsroom.co.nz/2018/05/02/106691/biofuels-z-energys-tortuous-carbon-solution">producing</a>). </p>
<p>A car running on fossil diesel emits about 2.7kg of carbon dioxide per litre and a petrol car produces 2.3kg per litre. Using biofuels to displace diesel or petrol can reduce emissions by up to 90% per kilometre if the biofuel is made from animal fat from a meat works. The amount varies depending on the source of the biofuel (sugarcane, wheat, oilseed rape). And of course it would be unacceptable if biofuel crops were replacing food crops or forests.</p>
<p>Regardless of the car, drivers can reduce fuel consumption by 15-20% by improving driving habits alone – reducing emissions and saving money at the same time. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/climate-explained-what-each-of-us-can-do-to-reduce-our-carbon-footprint-123851">Climate explained: what each of us can do to reduce our carbon footprint</a>
</strong>
</em>
</p>
<hr>
<h2>Fuel efficiency</h2>
<p>When you are thinking of replacing your car, taking into account fuel efficiency is another important way to save on fuel costs and reduce emissions.</p>
<p>Many countries, including the US, Japan, China and nations within the European Union, have had fuel efficiency standards for more than a decade. This has driven car manufacturers to design ever <a href="http://www.climatechangeauthority.gov.au/files/files/Light%20Vehicle%20Report/CCA_TransportReport_Appendices.WEB.pdf">more fuel-efficient vehicles</a>.</p>
<p>Most light-duty vehicles sold globally are subject to these standards. But Australia and New Zealand have both dragged the chain in this regard, partly because most vehicles are imported. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/australians-could-have-saved-over-1-billion-in-fuel-if-car-emissions-standards-were-introduced-3-years-ago-117190">Australians could have saved over $1 billion in fuel if car emissions standards were introduced 3 years ago</a>
</strong>
</em>
</p>
<hr>
<p>New Zealand also remains hesitant about introducing a “<a href="https://www.consumer.org.nz/articles/government-announces-consultation-light-vehicle-fleet-feebate">feebate</a>” scheme, which proposes a fee on imported high-emission cars to make imported hybrids, electric cars and other efficient vehicles cheaper with a subsidy.</p>
<p>In New Zealand, driving an <a href="https://theconversation.com/climate-explained-why-switching-to-electric-transport-makes-sense-even-if-electricity-is-not-fully-renewable-136502">electric car results in low emissions</a> because electricity generation is 85% renewable. In Australia, which still relies on coal-fired power, electric cars are responsible for higher emissions unless they are recharged through a local renewable electricity supply.</p>
<p>Fuel and electricity prices will inevitably rise. But whether we drive a petrol or electric car, we can all shield ourselves from some of those future price rises by driving more efficiently and less speedily. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/climate-explained-why-switching-to-electric-transport-makes-sense-even-if-electricity-is-not-fully-renewable-136502">Climate explained: why switching to electric transport makes sense even if electricity is not fully renewable</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/140246/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ralph Sims does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>You can reduce your fuel consumption by 15-20% with improved driving habits alone – reducing emissions and saving money at the same time.Ralph Sims, Professor, School of Engineering and Advanced Technology, Massey UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1386052020-06-02T20:03:50Z2020-06-02T20:03:50ZClimate explained: could the world stop using fossil fuels today?<figure><img src="https://images.theconversation.com/files/339065/original/file-20200602-95013-1q06695.jpg?ixlib=rb-1.1.0&rect=52%2C169%2C3852%2C2570&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Dave Greenberg/Shutterstock</span></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.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">
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<span class="attribution"><a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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<p><em><strong><a href="https://theconversation.com/nz/topics/climate-explained-74664">Climate Explained</a></strong> is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.</em> </p>
<p><em>If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz</em></p>
<blockquote>
<p><strong>If we stopped oil, gas and coal extraction immediately - what would happen? What would we need to change about the way our economies and societies work in order to adjust to that resource no longer being available? Do alternatives already exist that mean it could be business as usual if we (governments and individuals) make changes, or would it mean a major adjustment to the way we live our lives?</strong></p>
</blockquote>
<p>It is not feasible to immediately stop extracting and using fossil fuels. The global economy, human health and livelihoods currently depend heavily on oil, coal and gas. But over time, we need to displace fossil fuels with low-carbon renewable energy sources. </p>
<p>The first priority should be on switching to renewable energy, not just for electricity but also for heating, cooling and transport fuels. It will be much harder to substitute fossils fuels used for chemical processing, such as the manufacture of plastics or fertiliser, but it is technically possible with biomass (organic material from plants and animals). After all, the hydrocarbons in coal, oil and gas were originally derived from biomass millions of years ago. </p>
<p>The aim of governments, local and national, should be to encourage reduced use of fossil fuels by supporting renewable energy systems. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/climate-crisis-six-steps-to-making-fossil-fuels-history-127941">Climate crisis: six steps to making fossil fuels history</a>
</strong>
</em>
</p>
<hr>
<h2>Increasing contribution from renewables</h2>
<p>One issue is that <a href="https://theconversation.com/vast-subsidies-keeping-the-fossil-fuel-industry-afloat-should-be-put-to-better-use-119954">global subsidies</a> for fossil fuel extraction remain large, at around <a href="https://www.imf.org/en/Publications/WP/Issues/2019/05/02/Global-Fossil-Fuel-Subsidies-Remain-Large-An-Update-Based-on-Country-Level-Estimates-46509">US$4.7 trillion per year</a> according to the <a href="https://www.imf.org/external/index.htm">International Monetary Fund</a>.</p>
<p>In a recent <a href="https://www.iea.org/topics/covid-19">global energy review</a>, the <a href="https://www.iea.org/">International Energy Agency</a> described a significant drop in energy demand from fossil fuels as a <a href="https://www.iea.org/topics/covid-19">result of the COVID-19 pandemic</a>. Demand is likely to rise again, but in the meantime, the use of renewable electricity continues to increase and now has a <a href="https://www.iea.org/reports/tracking-power-2019/renewable-power">25% share of global electricity</a>. </p>
<p>Countries with good renewable resources can reach a significantly higher share. New Zealand, for example, now produces around 85% of its total electricity from renewable sources (including hydro, wind, solar and geothermal) without government intervention. But overall, renewable energy contributes only 40% of all energy demands in New Zealand, and far less globally.</p>
<p>There are many examples of how renewable energy can meet intensive industry demands, in New Zealand and elsewhere. New Zealand’s aluminium smelter uses electricity generated by the <a href="https://www.meridianenergy.co.nz/who-we-are/our-power-stations/hydro/manapouri">country’s largest hydro power station</a> built underground at Lake Manapōuri. A steel mill in Sweden uses “<a href="https://www.bloomberg.com/professional/blog/how-green-hydrogen-could-make-green-steel-real/">green hydrogen</a>”, produced by using renewable electricity to split water into hydrogen and oxygen. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/339068/original/file-20200602-95054-r57fj2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/339068/original/file-20200602-95054-r57fj2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=335&fit=crop&dpr=1 600w, https://images.theconversation.com/files/339068/original/file-20200602-95054-r57fj2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=335&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/339068/original/file-20200602-95054-r57fj2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=335&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/339068/original/file-20200602-95054-r57fj2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=420&fit=crop&dpr=1 754w, https://images.theconversation.com/files/339068/original/file-20200602-95054-r57fj2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=420&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/339068/original/file-20200602-95054-r57fj2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=420&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Manapōuri hydro power station supplies electricity to New Zealand’s aluminium smelter.</span>
<span class="attribution"><span class="source">Uwe Aranas/Shutterstock</span></span>
</figcaption>
</figure>
<p>Green hydrogen can also be used to displace natural gas for heating and cooking as well as for fuelling trucks, cars, <a href="https://www.mbie.govt.nz/dmsdocument/6798-a-vision-for-hydrogen-in-new-zealand-green-paper">boats</a> and <a href="https://www.forbes.com/sites/mikescott/2019/12/11/is-hydrogen-the-key-to-making-flying-zero-emission/#29ee5eba7242">planes</a>. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/immediate-phase-out-of-fossil-fuels-could-keep-warming-below-1-5-c-109672">Immediate phase out of fossil fuels could keep warming below 1.5°C</a>
</strong>
</em>
</p>
<hr>
<h2>The costs and benefits of change</h2>
<p>There are many alternatives to fossil fuels with far lower carbon footprints. This includes <a href="https://www.iaea.org/newscenter/news/iaea-climate-conference-ends-with-call-for-major-nuclear-role">electricity generated by nuclear power plants</a>. </p>
<p>But the problem is fossil fuels remain relatively cheap, because the cost of their <a href="https://www.nature.com/articles/d41586-017-07510-3">pollution isn’t usually factored in</a>, and energy dense (there is more energy contained in a lump of coal than a piece of wood of a similar size). Displacement is not easy and will take time to allow those working in the fossil fuel industry to go through a “<a href="https://theconversation.com/why-our-response-to-climate-change-needs-to-be-a-just-and-careful-revolution-that-limits-pushback-123588">just transition</a>” to work in other sectors.</p>
<p>Government intervention is often required for low-carbon options to increase their share in meeting total energy demands. But <a href="https://www.sciencedirect.com/science/article/pii/S2214629616300627">changing people’s behaviour</a> around energy use is more challenging than deploying new low-carbon technologies to provide the same energy services. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/why-our-response-to-climate-change-needs-to-be-a-just-and-careful-revolution-that-limits-pushback-123588">Why our response to climate change needs to be a just and careful revolution that limits pushback</a>
</strong>
</em>
</p>
<hr>
<p>We should not forget the additional benefits that come with a shift to low-carbon energy generation. More walking and cycling improves health, electric vehicles reduce local air pollution (compared with petrol and diesel vehicles) and using public transport and carrying more freight by rail can reduce traffic congestion. Other simple energy-saving measures – switching off lights, not wasting food – can all save money while lowering someone’s carbon footprint.</p>
<p>We have become a wasteful society, with consequences for the environment. Perhaps now is the time to make major adjustments to how we live before climate change impacts do it for us.</p><img src="https://counter.theconversation.com/content/138605/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ralph Sims does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>While it’s impossible to stop all extraction of fossil fuels now, renewable sources are already generating 25% of global electricity demand now and their contribution continues to grow.Ralph Sims, Professor, School of Engineering and Advanced Technology, Massey UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1386042020-05-26T20:08:56Z2020-05-26T20:08:56ZClimate explained: why countries don’t count emissions from goods they import<figure><img src="https://images.theconversation.com/files/337499/original/file-20200526-106853-jpo1fv.jpg?ixlib=rb-1.1.0&rect=57%2C188%2C5380%2C2240&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">SHeryl Williams/Shutterstock</span></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.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">
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<span class="attribution"><a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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<p><em><strong><a href="https://theconversation.com/nz/topics/climate-explained-74664">Climate Explained</a></strong> is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.</em> </p>
<p><em>If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz</em></p>
<blockquote>
<p><strong>I would like to know if New Zealand’s carbon emissions of 0.17% include emissions produced from products manufactured overseas and then imported for the New Zealand consumer?</strong></p>
</blockquote>
<p>The latest Ministry for the Environment <a href="https://www.mfe.govt.nz/sites/default/files/media/Climate%20Change/new-zealands-greenhouse-gas-inventory-1990-2018-snapshot.pdf">report</a>, published last month, shows New Zealand contributes 0.17% of the world’s total greenhouse gas emissions. </p>
<p>New Zealand’s population represents just 0.06% of the world’s population (New Zealand 5 million, global 7.8 billion), which means it has a disproportionately high share of emissions for its population size. This is sometimes represented as per capita emissions - and in 2017, New Zealand ranked sixth highest among <a href="https://www.oecd.org/env/cc/listofannexicountries.htm">developed and transitioning countries</a>, at <a href="https://www.mfe.govt.nz/sites/default/files/media/Climate%20Change/new-zealands-greenhouse-gas-inventory-1990-2018-snapshot.pdf">17.2 tonnes of carbon dioxide equivalent emissions per person</a>. This is almost three times the average per capita share.</p>
<p>The reason for this can be partly explained by the way countries account for their greenhouse gas emissions.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/climate-explained-which-countries-are-likely-to-meet-their-paris-agreement-targets-128855">Climate explained: which countries are likely to meet their Paris Agreement targets</a>
</strong>
</em>
</p>
<hr>
<h2>Keeping track of emissions of traded goods</h2>
<p>Countries generally use “<a href="https://www.researchgate.net/publication/334671079_Understanding_New_Zealand's_consumption-based_greenhouse_gas_emissions_an_application_of_multi-regional_input-output_analysis">production-based accounting</a>” to quantify their greenhouse gas emissions. This approach counts emissions from all activities that happen within a country’s territory - which means goods manufactured elsewhere and then imported are not included. </p>
<p>It also means that if a country exports more goods and services than it imports, it will likely have disproportionately higher per capita emissions. </p>
<p>It can be argued that if a country can produce these goods more efficiently (with lower emissions) than other countries, this may be the preferred situation. This is the case for New Zealand’s agricultural production. <a href="https://www.researchgate.net/publication/334671079_Understanding_New_Zealand's_consumption-based_greenhouse_gas_emissions_an_application_of_multi-regional_input-output_analysis">Research</a> shows New Zealand’s pasture-fed agricultural systems are efficient in producing meat and dairy products - per kilogram of meat or litre of milk, New Zealand emits less than many other countries. </p>
<p>Although most of these products are exported, the emissions from their production count towards New Zealand’s <a href="https://www.mfe.govt.nz/climate-change/state-of-our-atmosphere-and-climate/new-zealands-greenhouse-gas-inventory">greenhouse gas inventory</a>. In fact, almost half of New Zealand’s <a href="https://www.mfe.govt.nz/publications/climate-change/new-zealands-greenhouse-gas-inventory-1990-2018">emissions in 2018</a> came from agriculture, and just under three-quarters of these agricultural emissions were methane from cows and sheep.</p>
<p>From a global perspective, climate policy needs to recognise the advantage of producing goods where they can be <a href="https://www.tandfonline.com/doi/full/10.1080/14693062.2019.1619507">made with lower emissions</a>. Otherwise there is a risk industries relocate to other (typically less developed) countries with less stringent climate change regulations, and global greenhouse gas emissions rise as a result. This is known as “<a href="https://carbonmarketwatch.org/2014/08/29/carbon-leakage/">carbon leakage</a>”. </p>
<h2>Patterns of consumption</h2>
<p>But there is an important corollary to all of this: considering only the production-based emissions of countries is not enough to address the climate crisis. Even if New Zealand can produce agricultural goods more efficiently than other countries, should these be produced at the current volume - or at all? </p>
<p>Ultimately we need to consider patterns of consumption and assess whether they are in line with a sustainable future for the world. </p>
<p>In practical terms, this means that we should be accounting for both consumption and production-based emissions. An accounting system based on consumption would assess greenhouse gases emitted in the production of goods and services consumed by New Zealanders. This includes imported goods as well as everything that is produced and then consumed in New Zealand - and it excludes exported goods and services. </p>
<p>Two New Zealand studies (for <a href="https://pubs.acs.org/doi/10.1021/acs.est.9b06991?fig=fig1&ref=pdf">2011</a> and <a href="https://www.researchgate.net/publication/334671079_Understanding_New_Zealand's_consumption-based_greenhouse_gas_emissions_an_application_of_multi-regional_input-output_analysis">2012</a>) show the biggest contribution to consumption-based emissions comes from three sectors: construction, food and beverages, and education and health services. For food and beverages, animal protein and processed meat contributes <a href="https://ehp.niehs.nih.gov/doi/full/10.1289/EHP5996">35% of the emissions</a> associated with an average adult New Zealand diet. </p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/climate-explained-how-the-climate-impact-of-beef-compares-with-plant-based-alternatives-137787">Climate explained: how the climate impact of beef compares with plant-based alternatives</a>
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</em>
</p>
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<p>But accounting for emissions from consumption comes with challenges. It requires tracing the point of origin of imported products, often in countries with less stringent emission inventories. There are two types of modelling we can use to support consumption-based analysis. <a href="http://lcm.org.nz/">Life cycle assessment</a> starts with a product - say an apple or packet of milk powder - and tracks the entire supply chain back through the retail, distribution and agricultural production. Other models <a href="https://www.sciencedirect.com/science/article/pii/S0048969714003921">integrate environmental and economic data across multiple regions</a>. </p>
<p>Such data and the insights we glean from both production and consumption accounting could guide future climate policies to enable New Zealand to reduce emissions both within the country and internationally.</p><img src="https://counter.theconversation.com/content/138604/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sarah McLaren receives funding from AgResearch, BRANZ, Massey University, Ministry for Primary Industries, Plant and Food Research, Toitū.</span></em></p>Countries account for emissions based on all activities that happen within their territory, which means countries that export more than they import will likely have higher per capita emissions.Sarah McLaren, Professor of Life Cycle Management, Massey UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1386022020-05-19T07:03:06Z2020-05-19T07:03:06ZClimate explained: why we need to focus on increased consumption as much as population growth<figure><img src="https://images.theconversation.com/files/335290/original/file-20200515-138610-a2el71.jpg?ixlib=rb-1.1.0&rect=0%2C133%2C5559%2C3567&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Thomas La Mela/Shutterstock</span></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.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">
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<span class="attribution"><a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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<p><em><strong><a href="https://theconversation.com/nz/topics/climate-explained-74664">Climate Explained</a></strong> is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.</em> </p>
<p><em>If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz</em></p>
<blockquote>
<p><strong>Almost every threat to modern humanity can be traced simply to our out-of-control population growth (think about arable land going to housing; continued growth in demand for petroleum fuels). Is anything being done to contain population growth on a national and international scale?</strong></p>
</blockquote>
<p>The question of population is more complex that it may seem – in the context of climate change as well as other issues such as biodiversity loss and international development. </p>
<p>As a starting point, let’s look at the statement “out-of-control population growth”. In fact, population growth is more “in control” than it has been for the past 50 years.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/climate-explained-how-growth-in-population-and-consumption-drives-planetary-change-126671">Climate explained: how growth in population and consumption drives planetary change</a>
</strong>
</em>
</p>
<hr>
<h2>Population isn’t growing everywhere</h2>
<p>The <a href="https://www.worldometers.info/world-population/">global rate of population growth</a> has been declining from just over 2% per year in 1970 to less than 1.1% in 2020 (and this estimate was made before COVID-19 erupted globally).</p>
<p>To put this in perspective, if the 2% growth rate had continued, the world’s population would have doubled in 35 years. At a 1.1% growth rate, it would now be set to double in 63 years – but the growth rate is still declining, so the doubling time will be lengthened again.</p>
<p>Population growth also varies significantly between countries. Among the <a href="https://www.worldometers.info/world-population/population-by-country/">20 most populous countries in the world</a>, three countries have growth rates of more than 2.5% – Ethiopia, Nigeria and the Democratic Republic of Congo – while Japan’s population is in decline (with a negative growth rate, -0.3%) and China, Russia, Germany and Thailand all have very low growth rates.</p>
<p>These growth rates vary in part because the population structures are very different across countries. <a href="https://www.statista.com/statistics/270087/age-distribution-in-japan/">Japan</a> has an aged population, with 28% over 65 years and just 12% under 15 years. <a href="https://www.statista.com/statistics/382296/age-structure-in-nigeria/">Nigeria</a> has only 3% of people in the over-65 bracket and 44% under 15. </p>
<p>For comparison, 20% of New Zealanders are younger than 15 and 16% are older than 65. For Australia, the respective figures are 18% and 17%. </p>
<p>Migration also makes a significant contribution in some countries, propping up the working-age population and shaping the demographic structure. History and levels of economic development play an important role too: higher-income countries almost consistently have smaller families and lower growth rates. </p>
<h2>Rise in consumption</h2>
<p>It’s certainly valid to link population growth (even a more limited “in control” population growth) with climate change and loss of land. Everything else being equal, more people means more space taken up, more resources consumed and more carbon emitted. </p>
<p>But while population growth has slowed since the 1970s, resource consumption hasn’t. For example, there is no equivalent decline in <a href="https://ourworldindata.org/fossil-fuels">fossil fuel use</a> since the 1970s.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/335589/original/file-20200518-138639-u00co6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/335589/original/file-20200518-138639-u00co6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/335589/original/file-20200518-138639-u00co6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/335589/original/file-20200518-138639-u00co6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/335589/original/file-20200518-138639-u00co6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/335589/original/file-20200518-138639-u00co6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/335589/original/file-20200518-138639-u00co6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/335589/original/file-20200518-138639-u00co6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Fuel consumption varies throughout the world.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/mpcaphotos/22710974150/">Flickr/Minnesota Pollution Control Agency</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span>
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<p>This is an area where not everyone is equal. If all people were to use the same amount of resources (fossil fuels, timber, minerals, arable land etc), then of course total resource use and carbon would rise. But resource use varies dramatically globally. </p>
<p>If we look at <a href="https://www.indexmundi.com/g/r.aspx?v=91000">oil consumption per person</a> in 2019, the average American used almost twice as much as someone in Japan, the second oil-thirstiest populous nation, and almost 350 times as much as a person living in the Democratic Republic of Congo.</p>
<p>It is an easy out for us in the industrialised world to say “out-of-control population growth” is killing the planet, when instead it is equally valid – but more confronting – to say our out-of-control consumption is killing the planet.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/can-your-actions-really-save-the-planet-planetary-accounting-has-the-answer-104005">Can your actions really save the planet? 'Planetary accounting' has the answer</a>
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</em>
</p>
<hr>
<h2>Population growth slows when women are educated</h2>
<p>To come to the final part of the question: is anything being done to contain population growth, on a national or international scale?</p>
<p>Even if we set aside the argument above that population is not the only issue, or even the most significant one, in terms of threats to humanity, what factors might influence population growth in parts of the world where it is high?</p>
<p>Things are being done, but they may not be what most people expect. It has long been <a href="http://prelim2009.filmbulletin.org/readings/04-Population/Caldwell-Toward_a_Restatement_of_Demographic_Transition_Theory-1976.pdf">shown</a> that as incomes rise and health care improves, more children survive and people tend to have smaller families. </p>
<p>This effect is not instantaneous. There is a lag where population growth rates might rise first before they begin to drop. This demographic transition is a relatively consistent pattern globally. </p>
<p>But, at the country level, the single most significant influence on reducing fertility rates, family size and overall population growth is <a href="https://www.weforum.org/agenda/2015/07/how-education-can-moderate-population-growth/">access to education for girls and women</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/335592/original/file-20200518-138610-1y3pm5s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/335592/original/file-20200518-138610-1y3pm5s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/335592/original/file-20200518-138610-1y3pm5s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/335592/original/file-20200518-138610-1y3pm5s.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/335592/original/file-20200518-138610-1y3pm5s.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/335592/original/file-20200518-138610-1y3pm5s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/335592/original/file-20200518-138610-1y3pm5s.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/335592/original/file-20200518-138610-1y3pm5s.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">Fertility rates drop when girls get access to education.</span>
<span class="attribution"><span class="source">Oksana Kuzmina/Shutterstock</span></span>
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<p>One <a href="https://www.brookings.edu/blog/future-development/2016/02/16/climate-change-fertility-and-girls-education/">study in 2016</a>, drawing on World Bank population data across a wide range of countries, found:</p>
<blockquote>
<p>… the main driver of overall fertility reduction is clearly the change in proportions of women at each education level. </p>
</blockquote>
<p>In relation to climate change action, <a href="https://www.brookings.edu/blog/future-development/2016/02/16/climate-change-fertility-and-girls-education/">this study</a> specifically notes: </p>
<blockquote>
<p>It is education, or more specifically girls’ education, that is far more likely to result in lower carbon emissions than a shift to renewables, improved agricultural practices, urban public transport, or any other strategy now being contemplated.</p>
</blockquote>
<p>Recent <a href="https://www.pnas.org/content/113/50/14294/" title="Meeting the Sustainable Development Goals leads to lower world population growth">research</a> looked at how the global population might change if we implemented the aspirations of the 17 UN <a href="https://sustainabledevelopment.un.org/?menu=1300">Sustainable Development Goals</a>. It found the change would be significant and could even mean the global population stabilises by mid-century.</p><img src="https://counter.theconversation.com/content/138602/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Glenn Banks does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>It is easy for people in the industrialised world to blame population growth elsewhere for environmental damage. But increased consumption is just as important – if more confronting.Glenn Banks, Professor of Geography and Head of School, School of People, Environment and Planning, Massey UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1378742020-05-12T19:46:22Z2020-05-12T19:46:22ZClimate explained: what caused major climate change in the past?<figure><img src="https://images.theconversation.com/files/334197/original/file-20200512-66649-5piok4.jpg?ixlib=rb-1.1.0&rect=81%2C134%2C3813%2C2295&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><em><strong><a href="https://theconversation.com/nz/topics/climate-explained-74664">Climate Explained</a></strong> is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.</em> </p>
<p><em>If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz</em></p>
<blockquote>
<p><strong>Earth had several periods of high carbon dioxide levels in the atmosphere and high temperatures over the last several million years. Can you explain what caused these periods, given that there was no burning of fossil fuels or other sources of human created carbon dioxide release during those times?</strong></p>
</blockquote>
<p>Burning fossil fuels or vegetation is one way to put carbon dioxide into the air – and it is something we have become very good at. Humans are generating <a href="https://ourworldindata.org/co2-and-other-greenhouse-gas-emissions#how-have-global-co2-emissions-changed-over-time">nearly 40 billion tons of carbon dioxide</a> every year, mostly by burning fossil fuels. </p>
<p>Carbon dioxide stays in the air <a href="https://earthobservatory.nasa.gov/features/CarbonCycle/page5.php">for centuries to millennia</a> and it builds up over time. Since we began the systematic use of coal and oil for fuel, around 300 years ago, the amount of carbon dioxide in the air has gone up by almost half.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/334194/original/file-20200512-66698-lns3wx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/334194/original/file-20200512-66698-lns3wx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=369&fit=crop&dpr=1 600w, https://images.theconversation.com/files/334194/original/file-20200512-66698-lns3wx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=369&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/334194/original/file-20200512-66698-lns3wx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=369&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/334194/original/file-20200512-66698-lns3wx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=463&fit=crop&dpr=1 754w, https://images.theconversation.com/files/334194/original/file-20200512-66698-lns3wx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=463&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/334194/original/file-20200512-66698-lns3wx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=463&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="attribution"><span class="source">NOAA</span></span>
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<p>Apart from the emissions we add, carbon dioxide concentrations in the air go up and down as part of the natural <a href="https://earthobservatory.nasa.gov/features/CarbonCycle">carbon cycle</a>, driven by exchanges between the air, the oceans and the biosphere (life on earth), and ultimately by geological processes. </p>
<h2>Natural changes in carbon dioxide</h2>
<p>Every year, carbon dioxide concentrations rise and fall a little as plants grow in spring and summer and die off in the autumn and winter. The timing of this <a href="https://niwa.co.nz/atmosphere/our-data/trace-gas-plots/carbon-dioxide">seasonal rise and fall</a> is tied to northern hemisphere seasons, as most of the land surface on Earth is there. </p>
<p>The oceans also play an active role in the carbon cycle, contributing to variations over a few months to slow shifts over centuries. Ocean water takes up carbon dioxide directly in an exchange <a href="https://sos.noaa.gov/datasets/ocean-atmosphere-co2-exchange/">between the air and seawater</a>. Tiny marine plants use carbon dioxide for photosynthesis and many microscopic marine organisms use carbon compounds to make shells. When these marine micro-organisms die and sink to the seafloor, they take the carbon with them.</p>
<p>Collectively, the biosphere (ecosystems on land and in soils) and the oceans are absorbing about <a href="https://worldoceanreview.com/en/wor-1/ocean-chemistry/co2-reservoir/">half of all human-emitted carbon dioxide</a>, and this slows the rate of climate change. But as the climate continues to change and the oceans warm up further, it is not clear whether the biosphere and oceans will continue absorbing such a large fraction of our emissions. As water warms, it is less able to absorb carbon dioxide, and as the climate changes, many ecosystems become stressed and are less able to photosynthesise carbon dioxide.</p>
<h2>Earth’s deep climate history</h2>
<p>On time scales of hundreds of thousands to millions of years, carbon dioxide concentrations in the air have varied hugely, and so has global climate. </p>
<p>This <a href="https://www.skepticalscience.com/weathering.html">long-term carbon cycle</a> involves the formation and decay of the Earth’s surface itself: tectonic plate activity, the build-up and weathering of mountain chains, prolonged volcanic activity, and the emergence of new seafloor at active mid-ocean faults. </p>
<p>Most of the carbon stored in the Earth’s crust is in the form of limestone, created from the carbon-based shells of marine organisms that sank to the ocean floor millions of year ago.</p>
<p>Carbon dioxide is added to the air when volcanoes erupt, and it is taken out of the air as rocks and mountain ranges weather and wear down. These processes typically take millions of years to add or subtract carbon dioxide from the atmosphere. </p>
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Read more:
<a href="https://theconversation.com/climate-explained-how-volcanoes-influence-climate-and-how-their-emissions-compare-to-what-we-produce-125490">Climate explained: how volcanoes influence climate and how their emissions compare to what we produce</a>
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<p>In the present day, volcanoes add only a little carbon dioxide to the air, around <a href="https://www.skepticalscience.com/volcanoes-and-global-warming.htm">1% of what human activity is currently contributing</a>. But there have been times in the past where volcanic activity has been vastly greater and has spewed large amounts of carbon dioxide into the air.</p>
<p>An example is around 250 million years ago, when prolonged volcanic activity raised atmospheric carbon dioxide levels dramatically. These were volcanic eruptions on a vast scale - lasting for around two million years and <a href="https://www.sciencedaily.com/releases/2017/10/171002105227.htm">causing a mass extinction</a>.</p>
<p>In the more recent geological past, the past 50 million years, carbon dioxide levels have been gradually dropping overall and the climate has been cooling, with some ups and downs. Once carbon dioxide concentrations became low enough (around 300 parts per million) between two and three million years ago, the current ice age cycle began, but the warming our emissions are causing is larger than the natural cooling trend. </p>
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Read more:
<a href="https://theconversation.com/climate-explained-why-we-wont-be-heading-into-an-ice-age-any-time-soon-123675">Climate explained: why we won't be heading into an ice age any time soon</a>
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<p>While Earth’s climate has changed significantly in the past, it happened on geological time scales. The carbon in the oil and coal we burn represents carbon dioxide taken up by vegetation hundreds of millions of years ago and then deposited through geological processes over millennia. We have burned a significant proportion within a few centuries.</p>
<p>If human emissions of carbon dioxide continue to increase through this century, we could reach levels <a href="https://e360.yale.edu/features/how-the-world-passed-a-carbon-threshold-400ppm-and-why-it-matters">not seen for tens of millions of years</a>, when Earth had a much warmer climate with much higher sea levels and no ice sheets.</p><img src="https://counter.theconversation.com/content/137874/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>James Renwick receives funding from the NZ Ministry for Business, Innovation and Employment. He is affiliated with the NZ Climate Change Commission. </span></em></p>Earth’s has gone through major climate changes in the past. They happened on time scales of millions of years and triggered mass extinctions. Our emissions are changing the climate much faster.James Renwick, Professor, Physical Geography (climate science), Te Herenga Waka — Victoria University of WellingtonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1377872020-05-05T19:53:40Z2020-05-05T19:53:40ZClimate explained: how the climate impact of beef compares with plant-based alternatives<figure><img src="https://images.theconversation.com/files/332552/original/file-20200504-83730-1qof1ab.jpg?ixlib=rb-1.1.0&rect=59%2C130%2C3894%2C2501&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><em><strong><a href="https://theconversation.com/nz/topics/climate-explained-74664">Climate Explained</a></strong> is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.</em> </p>
<p><em>If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz</em></p>
<blockquote>
<p><strong>I am wondering about the climate impact of vegan meat versus beef. How does a highly processed patty compare to butchered beef? How does agriculture of soy (if this is the ingredient) compare to grazing of beef?</strong></p>
</blockquote>
<p>Both <a href="https://impossiblefoods.com/mission/lca-update-2019/">Impossible Foods</a> and <a href="http://css.umich.edu/publication/beyond-meats-beyond-burger-life-cycle-assessment-detailed-comparison-between-plant-based">Beyond Meat</a>, two of the biggest players in the rapidly expanding meat alternatives market, claim their vegan burger patties (made primarily from a variety of plant proteins and oils) are 90% less climate polluting than a typical beef patty produced in the United States.</p>
<p>The lifecycle assessments underpinning these findings were funded by the companies themselves, but the results make sense in the context of international research, which has repeatedly shown plant foods are significantly <a href="https://www.thelancet.com/journals/lanplh/article/PIIS2542-5196(18)30206-7/fulltext">less environmentally damaging than animal foods</a>.</p>
<p>It is worth asking what these findings would look like if the impacts of plant-based meats had been compared with a beef patty produced from a grass-fed
cattle farm, as is the case in New Zealand, instead of an industrialised feedlot operation that is commonplace in the United States.</p>
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Read more:
<a href="https://theconversation.com/climate-explained-will-we-be-less-healthy-because-of-climate-change-115800">Climate explained: will we be less healthy because of climate change?</a>
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<h2>A New Zealand perspective</h2>
<p>Building on international research mainly carried out in the Northern Hemisphere, we recently completed a <a href="https://ehp.niehs.nih.gov/doi/full/10.1289/EHP5996">full assessment</a> of the greenhouse gas emissions associated with different foods and dietary patterns in New Zealand.</p>
<p>Despite <a href="https://www.rnz.co.nz/news/country/396339/new-zealand-meat-production-systems-part-of-the-solution-for-climate-change-nz-beef-lamb">dominant narratives</a> about the efficiency of New Zealand’s livestock production systems, we found the stark contrast between climate impacts of plant and animal foods is as relevant in New Zealand as it is elsewhere. </p>
<p>For example, we found 1 kilogram of beef purchased at the supermarket produces 14 times the emissions of whole, protein-rich plant foods like lentils, beans and chickpeas. Even the most emissions-intensive plant foods, such as rice, are still more than four times more climate-friendly than beef.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/332491/original/file-20200504-83775-zfd56z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/332491/original/file-20200504-83775-zfd56z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/332491/original/file-20200504-83775-zfd56z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=615&fit=crop&dpr=1 600w, https://images.theconversation.com/files/332491/original/file-20200504-83775-zfd56z.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=615&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/332491/original/file-20200504-83775-zfd56z.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=615&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/332491/original/file-20200504-83775-zfd56z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=773&fit=crop&dpr=1 754w, https://images.theconversation.com/files/332491/original/file-20200504-83775-zfd56z.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=773&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/332491/original/file-20200504-83775-zfd56z.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=773&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 New Zealand food emissions database: comparing the climate impact of commonly consumed food items in New Zealand.</span>
<span class="attribution"><span class="source">Drew et al., 2020</span></span>
</figcaption>
</figure>
<p>The climate impact of different foods is largely determined by the on-farm stage of production. Other lifecycle stages such as processing, packaging and transportation play a much smaller role. </p>
<p>Raising beef cattle, regardless of the production system, releases large quantities of methane as the animals belch the gas while they chew the cud. Nitrous oxide released from fertilisers and manure is another potent greenhouse gas that drives up beef’s overall climate footprint.</p>
<h2>Climate impact of the New Zealand diet</h2>
<p>Everyday food choices can make a difference to the overall climate impact of our diet. In our modelling of different eating patterns, we found every step New Zealand adults take towards eating a more plant-based diet results in lower emissions, better population health and reduced healthcare costs.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/332495/original/file-20200504-83775-yqubxi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/332495/original/file-20200504-83775-yqubxi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/332495/original/file-20200504-83775-yqubxi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=649&fit=crop&dpr=1 600w, https://images.theconversation.com/files/332495/original/file-20200504-83775-yqubxi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=649&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/332495/original/file-20200504-83775-yqubxi.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=649&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/332495/original/file-20200504-83775-yqubxi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=815&fit=crop&dpr=1 754w, https://images.theconversation.com/files/332495/original/file-20200504-83775-yqubxi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=815&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/332495/original/file-20200504-83775-yqubxi.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=815&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Climate impact of different dietary scenarios, as compared with the typical New Zealand diet.</span>
<span class="attribution"><span class="source">Drew et al., 2020</span></span>
</figcaption>
</figure>
<p>The graph above shows a range of dietary changes, which gradually replace animal-based and highly processed foods with plant-based alternatives. If all New Zealand adults were to adopt a vegan diet with no food wastage, we estimated diet-related emissions could be reduced by 42% and healthcare costs could drop by NZ$20 billion over the lifetime of the current New Zealand population.</p>
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Read more:
<a href="https://theconversation.com/a-vegan-meat-revolution-is-coming-to-global-fast-food-chains-and-it-could-help-save-the-planet-115529">A vegan meat revolution is coming to global fast food chains – and it could help save the planet</a>
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<h2>Redesigning the food system</h2>
<p>The current global food system is <a href="https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(18)32822-8/fulltext">wreaking havoc</a> on both human and planetary health. Our work adds to an already strong body of <a href="https://eatforum.org/content/uploads/2019/07/EAT-Lancet_Commission_Summary_Report.pdf">international research</a> that shows less harmful alternatives are possible. </p>
<p>As pressure mounts on governments around the world to help redesign our food systems, policymakers continue to show reluctance when it comes to supporting a transition toward plant-based diets. </p>
<p>Such inaction appears, in large part, to be driven by the propagation of <a href="https://www.mdpi.com/2072-6643/11/10/2544/htm">deliberate misinformation by powerful food industry groups</a>, which not only confuses consumers but undermines the development of healthy and sustainable public policy.</p>
<p>To address the <a href="https://science.sciencemag.org/content/347/6223/1259855">multiple urgent environmental health issues</a> we face, a shift towards a plant-based diet is something many individuals can do for their and the planet’s health, while also pressing for the organisational and policy changes needed to make such a shift affordable and accessible for everyone.</p><img src="https://counter.theconversation.com/content/137787/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alexandra Macmillan is the unpaid co-convenor of OraTaiao: NZ Climate & Health Council, a not-for-profit incorporated society of health professionals advocating for evidence-based healthy, equitable policy responses to climate change. </span></em></p><p class="fine-print"><em><span>Jono Drew co-runs The Mouthful, a non-profit website that posts articles about food system sustainability. The Mouthful does not receive any funding, nor does it accept donations.</span></em></p>Food choices make a difference to the climate impact of our diet. Every step towards eating a more plant-based diet results in lower emissions, better population health and reduced healthcare costs.Alexandra Macmillan, Associate Professor Environment and Health, University of OtagoJono Drew, Medical Student, University of OtagoLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1372352020-04-28T19:52:12Z2020-04-28T19:52:12ZClimate explained: why higher carbon dioxide levels aren’t good news, even if some plants grow faster<figure><img src="https://images.theconversation.com/files/330586/original/file-20200427-163122-wo4504.jpg?ixlib=rb-1.1.0&rect=29%2C83%2C3956%2C2067&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><em><strong><a href="https://theconversation.com/nz/topics/climate-explained-74664">Climate Explained</a></strong> is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.</em> </p>
<p><em>If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz</em></p>
<blockquote>
<p><strong>If carbon dioxide levels were to double, how much increase in plant growth would this cause? How much of the world’s deserts would disappear due to plants’ increased drought tolerance in a high carbon dioxide environment?</strong> </p>
</blockquote>
<p>Compared to pre-industrial levels, the concentration of carbon dioxide (CO₂) in the atmosphere will have doubled in about 20 to 30 years, depending on how much CO₂ we emit over the coming years. More CO₂ generally leads to higher rates of photosynthesis and less water consumption in plants. </p>
<p>At first sight, it seems more CO₂ can only be beneficial to plants, but things are a lot more complex than that.</p>
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<strong>
Read more:
<a href="https://theconversation.com/climate-explained-why-plants-dont-simply-grow-faster-with-more-carbon-dioxide-in-air-115907">Climate explained: why plants don't simply grow faster with more carbon dioxide in air</a>
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<p>Let’s look at the first part of the question. </p>
<p>Some plants do grow faster under elevated levels of atmospheric CO₂, but this happens mostly in <a href="https://www.sciencedirect.com/science/article/abs/pii/S0098847215300253">crops</a> and young trees, and generally not in <a href="https://www.nature.com/articles/s41586-020-2128-9?proof=trueHere">mature forests</a>. </p>
<p>Even if plants grew twice as fast under doubled CO₂ levels, it would not mean they strip twice as much CO₂ from the atmosphere. Plants take carbon from the atmosphere as they grow, but that carbon is going straight back via natural decomposition when plants die or when they are harvested and consumed.</p>
<p>At best, you might be <a href="https://theconversation.com/climate-explained-why-your-backyard-lawn-doesnt-help-reduce-carbon-dioxide-in-the-atmosphere-122312">mowing your lawn twice as often</a> or harvesting your plantation forests earlier. </p>
<p>The most important aspect is how long the carbon stays locked away from the atmosphere - and this is where we have to make a clear distinction between increased carbon flux (faster growth) or an increasing carbon pool (<a href="https://science.sciencemag.org/content/355/6321/130.summary">actual carbon sequestration</a>). Your bank account is a useful analogy to illustrate this difference: fluxes are transfers, pools are balances. </p>
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Read more:
<a href="https://theconversation.com/climate-explained-why-your-backyard-lawn-doesnt-help-reduce-carbon-dioxide-in-the-atmosphere-122312">Climate explained: why your backyard lawn doesn't help reduce carbon dioxide in the atmosphere</a>
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<h2>The global carbon budget</h2>
<p>Of the almost 10 billion tonnes (gigatonnes, or Gt) of carbon we emit every year through the burning of fossil fuels, only about half accumulates in the atmosphere. Around a quarter ends up in the ocean (about 2.4 Gt), and the remainder (about 3 Gt) is thought to be <a href="https://www.earth-syst-sci-data.net/10/2141/2018/">taken up by terrestrial plants</a>. </p>
<p>While the ocean and the atmospheric sinks are relatively easy to quantify, the terrestrial sink isn’t. In fact, the 3 Gt can be thought of more as an unaccounted residual. Ultimately, the emitted carbon needs to go somewhere, and if it isn’t the ocean or the atmosphere, it must be the land.</p>
<p>So yes, the terrestrial system takes up a substantial proportion of the carbon we emit, but the attribution of this sink to elevated levels of CO₂ is difficult. This is because many other factors may contribute to the land carbon sink: rising temperature, increased use of fertilisers and atmospheric nitrogen deposition, changed land management (including land abandonment), and changes in species composition. </p>
<p><a href="http://dx.doi.org/10.1038/s41598-017-03818-2">Current estimates</a> assign about a quarter of this land sink to elevated levels of CO₂, but estimates are very uncertain. </p>
<p>In summary, rising CO₂ leads to faster plant growth - sometimes. And this increased growth only partly contributes to sequestering carbon from the atmosphere. The important questions are how long this carbon is locked away from the atmosphere, and how much longer the <a href="https://www.nature.com/articles/s41559-017-0274-8">currently observed land sink will continue</a>. </p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/climate-explained-how-different-crops-or-trees-help-strip-carbon-dioxide-from-the-air-123590">Climate explained: how different crops or trees help strip carbon dioxide from the air</a>
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<p>The second part of the question refers to a side-effect of rising levels of CO₂ in the air: the fact that it enables plants to save water. </p>
<p>Plants regulate the exchange of carbon dioxide and water vapour by opening or closing small pores, called stomata, on the surface of their leaves. Under higher concentrations of CO₂, they can reduce the opening of these pores, and that in turn means they <a href="https://theconversation.com/rising-carbon-dioxide-is-making-the-worlds-plants-more-water-wise-79427">lose less water</a>. </p>
<p>This alleviates drought stress in already dry areas. But again, the issue is more complex because CO₂ is not the only parameter that changes. Dry areas also get warmer, which means that more water evaporates and this often compensates for the water-saving effect.</p>
<p>Overall, rising CO₂ has contributed to some degree to the <a href="https://www.nature.com/articles/nclimate3004">greening of Earth</a>, but it is likely that this trend will not continue under the much more complex combination of global change drivers, particularly in <a href="https://www.sciencedirect.com/science/article/abs/pii/S0098847217301168">arid regions</a>.</p><img src="https://counter.theconversation.com/content/137235/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sebastian Leuzinger receives funding from the Royal Society. </span></em></p>Plants take carbon from the atmosphere as they grow, but it goes straight back when they die or are harvested. There is an important difference between carbon fluxes and actual carbon sequestration.Sebastian Leuzinger, Professor, Auckland University of TechnologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1365022020-04-21T20:07:03Z2020-04-21T20:07:03ZClimate explained: why switching to electric transport makes sense even if electricity is not fully renewable<figure><img src="https://images.theconversation.com/files/329302/original/file-20200421-126541-53o8hv.jpg?ixlib=rb-1.1.0&rect=38%2C114%2C5054%2C3275&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><em><strong><a href="https://theconversation.com/nz/topics/climate-explained-74664">Climate Explained</a></strong> is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.</em> </p>
<p><em>If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz</em></p>
<blockquote>
<p><strong>I have a question about the charging of electric cars. I understand New Zealand is not 100% self-sufficient in renewable energy (about 80%, supplemented by 20% generally produced by coal-fired stations). If I were to buy an electric vehicle it would add to the load on the national grid. Is the only way we are currently able to add the extra power to burn more coal? Does this not make these vehicles basically “coal fired”?</strong></p>
</blockquote>
<p>New Zealand is indeed well supplied with renewable electricity. In recent years, New Zealand <a href="https://www.mbie.govt.nz/building-and-energy/energy-and-natural-resources/energy-statistics-and-modelling/energy-publications-and-technical-papers/new-zealand-energy-quarterly/">has averaged</a> 83% from renewable sources (including 60% hydropower, 17% geothermal, and 5% wind) and 17% from fossil fuels (4% coal and 13% gas). </p>
<p>In addition to being cheap and renewable, hydropower has another great advantage. Its production can ramp up and down very quickly (by turning the turbines on and off) during the day to match demand.</p>
<p>Looking at a typical winter’s day (I’ve taken <a href="https://web.archive.org/web/20180704063721/http:/www.em6live.co.nz/Default.aspx">July 4, 2018</a>), demand at 3am was 3,480 megawatts (MW) and 85% was met by renewable sources. By the early evening peak, demand was up to 5,950MW, but was met by 88% renewable sources. Fossil fuel sources did ramp up, but hydropower ramped up much more. </p>
<h2>Flipping the fleet</h2>
<p>Even during periods of peak demand, our electricity is very clean. An electric vehicle (EV) charged during the evening would <a href="https://www.nature.com/articles/s41893-020-0488-7">emit about 20 grams of carbon dioxide per kilometre</a>.</p>
<p>Even an EV charged purely on coal- or gas-fired electricity still has <a href="https://www.eeca.govt.nz/news-and-events/media-releases/research-confirms-environmental-benefits-of-electric-vehicles/">lower emissions than a petrol or diesel car</a>, which comes to around 240g CO₂/km (if one includes the emissions needed to extract, refine, and transport the fuel). </p>
<p>An EV run on coal-fired electricity emits around 180g CO₂/km during use, while the figure for gas-fired electricity is about 90g CO₂/km. This is possible because internal combustion engines are less efficient than the turbines used in power stations.</p>
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Read more:
<a href="https://theconversation.com/climate-explained-the-environmental-footprint-of-electric-versus-fossil-cars-124762">Climate explained: the environmental footprint of electric versus fossil cars</a>
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<p>Looking longer term, a mass conversion of transport in New Zealand to walking, cycling and electric trains, buses, cars and trucks is one of the best and most urgent <a href="https://www.productivity.govt.nz/inquiries/lowemissions/">strategies</a> to reduce emissions. It will take a few decades, but on balance it may not be too expensive, because of the fuel savings that will accrue (<a href="https://www.stats.govt.nz/reports/overseas-goods-trade-2018-in-review">NZ$11 billion</a> of fuel was imported in 2018.)</p>
<p>This conversion will increase electricity use by about a <a href="https://www.transpower.co.nz/news/transpower-report-opportunity-decarbonise-our-economy">quarter</a>. To meet it we can look at both supply and demand.</p>
<h2>More renewable electricity</h2>
<p>On the supply side, more renewable electricity is planned – construction of three large wind farms began in 2019, and more are <a href="http://www.windenergy.org.nz/wind-energy/nz-windfarms">expected</a>. The potential supply is significant, especially considering that, compared to many other countries, we’ve hardly begun to start using <a href="https://www.transpower.co.nz/about-us/transmission-tomorrow/sun-rises-solar-energy-future">solar power</a>. </p>
<p>But at some point, adding too much of these intermittent sources starts to strain the ability of the hydro lakes to balance them. This is at the core of the present <a href="https://www.transpower.co.nz/news/transpower-report-opportunity-decarbonise-our-economy">debate</a> about whether New Zealand should be aiming for 100% or <a href="https://www.stuff.co.nz/business/113730079/experts-warn-100-renewable-electricity-target-will-hurt-new-zealands-wider-climate-goals">95%</a> renewable electricity. </p>
<p>There are various ways of dealing with this, including storage batteries, building more geothermal power stations or “<a href="https://www.odt.co.nz/regions/central-otago/massive-hydro-storage-plan-be-reassessed">pumped hydro</a>” stations. In pumped hydro, water is pumped uphill into a storage lake when there is an excess of wind and solar electricity available, to be released later. If the lake is large enough, this technology can also address New Zealand’s persistent risk of dry years that can lead to a shortage of hydropower.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/climate-explained-why-dont-we-have-electric-aircraft-123910">Climate explained: why don't we have electric aircraft?</a>
</strong>
</em>
</p>
<hr>
<h2>Smarter electricity use</h2>
<p>On the demand side, a survey is <a href="https://flipthefleet.org/2018/drivers-memo-27/">under way</a> to measure the actual charging patterns of EV drivers. Information available so far suggests that many people charge their EV late at night to take advantage of cheap night rates. </p>
<p>If demand gets too high at certain times, then the cost of both generation and transmission will likely rise. To avoid this, electricity suppliers are exploring smart <a href="https://www.transpower.co.nz/keeping-you-connected/demand-response/our-demand-response-programme-0">demand responses</a>, based on the hot water ripple control New Zealand began using in the 1950s. This allows electricity suppliers to remotely turn off hot water heaters for a few hours to limit demand. </p>
<p>In modern versions, consumers or suppliers can moderate demand in response to price signals, either in real time using an app or ahead of time through a contract.</p>
<p>New Zealand’s emissions from land transport continue to rise, up by another <a href="https://emissionstracker.mfe.govt.nz/">2% in 2018</a> and almost double on 1990 levels. </p>
<iframe title="Emissions from land transport in New Zealand" aria-label="Column Chart" src="https://datawrapper.dwcdn.net/VQXJ1/1/" scrolling="no" frameborder="0" style="border: none;" width="100%" height="400"></iframe>
<p>To address climate change, we have to stop burning fossil fuels. Passenger cars are among the biggest users and also one of the easiest to change. Fossil fuel cannot be recycled or made clean. In contrast, electricity is getting cleaner all the time, both in New Zealand and in car factories.</p>
<p>If you switch to an EV now, your impact is far greater than just your personal reduction in emissions. Early adopters are <a href="https://en.wikipedia.org/wiki/Diffusion_of_innovations">vital</a>. The more EVs we have, the more people will get used to them, the easier it will be to counter misinformation, and the more pressure there will be to cater for them. </p>
<p>Many people have found that switching to an electric car has been empowering and has <a href="https://www.psychology.org.au/getmedia/88ee1716-2604-44ce-b87a-ca0408dfaa12/Climate-change-empowerment-handbook.pdf">galvanised</a> them to start taking other actions for the climate.</p><img src="https://counter.theconversation.com/content/136502/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Robert McLachlan does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>A switch to electric transport is one of New Zealand’s key climate strategies. It will increase demand on the national grid, but might also help increase renewable electricity generation.Robert McLachlan, Professor in Applied Mathematics, Massey UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1346242020-04-21T13:22:06Z2020-04-21T13:22:06ZThe urban forest of the future: how to turn our cities into Treetopias<figure><img src="https://images.theconversation.com/files/329144/original/file-20200420-152558-v13czc.jpg?ixlib=rb-1.1.0&rect=12%2C0%2C4181%2C2791&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/view-skyscrapers-manhattan-through-trees-on-470086562">Drop of Light/Shutterstock</a></span></figcaption></figure><p>The 21st century is the urban century. It has been forecast that urban areas across the world will have expanded by more than <a href="https://www.un.org/en/development/desa/publications/2014-revision-world-urbanization-prospects.html">2.5 billion people</a> by 2050.</p>
<p>The scale and speed of urbanisation has created significant environmental and health problems for urban dwellers. These problems are often made worse by a lack of contact with the natural world.</p>
<p>With research group the <a href="https://evolvingtheforest.uk/shop/roundtable-tree_urbanistas/">Tree Urbanistas</a>, I have been considering and debating how to solve these problems. By 2119, it is only through re-establishing contact with the natural world, particularly trees, that cities will be able to function, be viable and able to support their populations. </p>
<h2>Future cities</h2>
<p>The creation of urban forests will make cities worth living in, able to function and support their populations: Treetopias. </p>
<p>This re-design will include the planting of many more urban trees and other vegetation – and making use of new, more creative methods. Although we didn’t fully realise it at the time, the 1986 <a href="https://www.wien.info/en/sightseeing/sights/hundertwasser-house-vienna">Hundertwasserhaus</a> in Vienna, a building that incorporated 200 trees in its design, was the start of more creative urban forestry thinking. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/329142/original/file-20200420-152558-1rrhpbx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/329142/original/file-20200420-152558-1rrhpbx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/329142/original/file-20200420-152558-1rrhpbx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/329142/original/file-20200420-152558-1rrhpbx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/329142/original/file-20200420-152558-1rrhpbx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=565&fit=crop&dpr=1 754w, https://images.theconversation.com/files/329142/original/file-20200420-152558-1rrhpbx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=565&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/329142/original/file-20200420-152558-1rrhpbx.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">
<figcaption>
<span class="caption">The Hundertwasserhaus in Vienna, designed by Friedensreich Hundertwasser.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/vienna-austria-october-09-2016-hundertwasserhaus-499580656">photosounds/Shutterstock</a></span>
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<p>This has been carried on in Stefano Boeri’s <a href="https://www.stefanoboeriarchitetti.net/en/project/vertical-forest/">Bosco Verticale</a> apartments in downtown Milan, which incorporates over 800 trees as part of the building. Similar structures are being developed around the world, such as in <a href="https://www.thenanjinger.com/news/nanjing-news/vertical-forest-nanjing-grows-learning-bosco-verticale/">Nanjing</a> in China and <a href="https://www.stefanoboeriarchitetti.net/en/project/wonderwoods/">Utrecht</a> in The Netherlands.</p>
<p>The urban forest needs to be designed as a first principle, part of the critical infrastructure of the whole city, not just as a cosmetic afterthought. We know for example that in 2015, urban forest in the UK saved the NHS over £1 billion by helping to reduce the impact of <a href="https://inews.co.uk/news/environment/trees-plants-grass-save-30000-lives-2015-uk-removing-pollution-509182">air pollutants</a>. In 2119, we may well look back on this present time as the equivalent of the Victorian slum.</p>
<p>Trees can create places which can greatly improve our health and well-being. Our urban forest can give us the spaces and places to help manage our mental health and improve our physical health. <a href="https://www.fs.usda.gov/treesearch/pubs/54105">Research has indicated</a> for example that increasing the canopy cover of a neighbourhood by 10% and creating safe, walkable places can reduce obesity by as much as 18%.</p>
<h2>Cities built on trees</h2>
<p>As rural areas become less productive as a result of climate change, cities – which previously consumed goods and services from a large hinterland – will have to become internally productive. Trees will be at the centre of that, contributing to the city energy balance through cooling, regulating and cleaning our air and water flows, and ensuring that our previously neglected urban soils function healthily. </p>
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<img alt="" src="https://images.theconversation.com/files/329141/original/file-20200420-152597-1kckql.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/329141/original/file-20200420-152597-1kckql.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/329141/original/file-20200420-152597-1kckql.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/329141/original/file-20200420-152597-1kckql.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/329141/original/file-20200420-152597-1kckql.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/329141/original/file-20200420-152597-1kckql.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/329141/original/file-20200420-152597-1kckql.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Bosco Verticale (Vertical Forest) in Milan, designed by Stefano Boeri.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/milan-italymay-2018-bosco-verticale-innovative-1091092670">Sabino Parente/Shutterstock</a></span>
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<p>Urban forests could also provide timber for building. We have a history of productive woodlands in the UK, yet alternative construction materials and a growth in an urban population with less knowledge of forest management means that the urban forest is rarely viewed as productive. We are now recognising the potential productivity of the urban forest, as campaigns to stimulate homegrown timber markets and achieve more efficient management efficiencies are <a href="https://www.springer.com/gp/book/9781402083709">proving to be successful</a>.</p>
<p>Furthermore, economic growth is still deemed to be the prime symbol of the effectiveness of a city, but we need to be equally aware of other invisible values. This will open up new approaches to governance. Governance needs to embrace all forms of value in a balanced way and facilitate a new vision, considering how trees can help create liveable cities. </p>
<h2>New opportunities</h2>
<p>As the urban population rises, we need to get better at understanding the breadth and diversity of the values held about our urban forest. Individual people can hold several distinct values at once, as urban forests may contribute to their wellbeing in different ways.</p>
<p>The current guardians of our urban forest, mainly local authority tree officers, spend much of their time managing risks rather than maximising the opportunities of trees. They often receive complaints about trees and tree management, and it can sometimes be difficult to remember that people do care about trees. We need to develop viable partnerships between tree managers, community members and businesses to support trees in our cities.</p>
<p>Although the canopy cover of cities worldwide is currently falling, this is not the case in Europe, where <a href="https://www.fs.fed.us/nrs/pubs/jrnl/2020/nrs_2020_nowak_002.pdf">it is increasing</a>. Many European countries are acknowledging the fact that we have over-designed our towns and cities to accommodate the car, and now it is time to reclaim the public realm for our people – either pedestrians on foot or on bicycles. </p>
<p>Creative developments like the Hundertwasserhaus are not the only answer to creating Treetopia. We are and will continue to plant more street trees, urban groves and informal clusters of trees in our parks and green spaces. Treetopia has begun. </p>
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<img alt="" src="https://images.theconversation.com/files/290123/original/file-20190829-106524-1w6rzla.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/290123/original/file-20190829-106524-1w6rzla.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=446&fit=crop&dpr=1 600w, https://images.theconversation.com/files/290123/original/file-20190829-106524-1w6rzla.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=446&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/290123/original/file-20190829-106524-1w6rzla.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=446&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/290123/original/file-20190829-106524-1w6rzla.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=560&fit=crop&dpr=1 754w, https://images.theconversation.com/files/290123/original/file-20190829-106524-1w6rzla.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=560&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/290123/original/file-20190829-106524-1w6rzla.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=560&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p><strong><em>This article is part of <a href="https://www.cjr.org/covering_climate_now/covering-climate-partnerships.php/">The Covering Climate Now</a> series</em></strong>
<br><em>This is a concerted effort among news organisations to put the climate crisis at the forefront of our coverage. This article is published under a Creative Commons license and can be reproduced for free – just hit the “Republish this article” button on the page to copy the full HTML coding. The Conversation also runs Imagine, a newsletter in which academics explore how the world can rise to the challenge of climate change. <a href="https://theconversation.com/imagine-newsletter-researchers-think-of-a-world-with-climate-action-113443?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=CoveringClimateNow">Sign up here</a></em>.</p>
<hr><img src="https://counter.theconversation.com/content/134624/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alan Simson does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>We must re-establish contact between our cities and the natural world.Alan Simson, Professor of Landscape Architecture and Urban Forestry, Leeds Beckett UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1289182020-04-14T19:54:04Z2020-04-14T19:54:04ZClimate explained: how white roofs help to reflect the sun’s heat<figure><img src="https://images.theconversation.com/files/313599/original/file-20200204-41485-1n70hqk.jpg?ixlib=rb-1.1.0&rect=50%2C184%2C5557%2C3547&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">www.shutterstock.com</span></span></figcaption></figure><p><em><strong><a href="https://theconversation.com/nz/topics/climate-explained-74664">Climate Explained</a></strong> is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.</em> </p>
<p><em>If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz</em></p>
<blockquote>
<p><strong>Does the white roof concept really work? If so, is it suitable for New Zealand conditions?</strong></p>
</blockquote>
<p>Generally, white materials reflect more light than dark ones, and this is also true for buildings and infrastructure. The outside and roof of a building soak up the heat from the sun, but if they are made of materials and finishes in lighter or white colours, this can minimise this solar absorption. </p>
<p>During the warmer part of the year, this can keep the temperature inside the building cooler. This is especially important for building and construction materials such as concrete, stone and asphalt, which store and re-radiate heat. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/climate-explained-which-countries-are-likely-to-meet-their-paris-agreement-targets-128855">Climate explained: which countries are likely to meet their Paris Agreement targets</a>
</strong>
</em>
</p>
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<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/313603/original/file-20200204-41485-16nvg47.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/313603/original/file-20200204-41485-16nvg47.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/313603/original/file-20200204-41485-16nvg47.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/313603/original/file-20200204-41485-16nvg47.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/313603/original/file-20200204-41485-16nvg47.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/313603/original/file-20200204-41485-16nvg47.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/313603/original/file-20200204-41485-16nvg47.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">On a hot day, a white roof can keep the temperature cooler inside the building.</span>
<span class="attribution"><span class="source">from www.shutterstock.com</span></span>
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<p>A <a href="https://www.tandfonline.com/doi/abs/10.1080/2093761X.2016.1167644">New Zealand study</a> tested near-identical buildings in Auckland with either a red or white roof. It found that even in Auckland’s temperate climate, white roofs reduced the need for air conditioning during hotter periods, without reducing comfort during cooler seasons. </p>
<p>The study also identified several large-scale white-roof installations, including at Auckland International Airport, shopping centres and commercial buildings, but the effect was less clear. </p>
<p>This research suggests that there is potential for white-roof installations to significantly reduce the amount of energy needed to cool buildings. This would in turn reduce greenhouse gas emissions and also help us to adapt to rising temperatures. </p>
<p>It is difficult to quantify the impact for New Zealand’s housing stock because existing studies are mostly limited to larger commercial buildings. But research carried out so far suggests white roofs could be a viable approach to minimising the heat taken up by buildings during hotter parts of the year. </p>
<h2>Cooling cities</h2>
<p>White roofs can also help <a href="https://e360.yale.edu/features/urban-heat-can-white-roofs-help-cool-the-worlds-warming-cities">reduce the temperature of whole cities</a>. Many city centres include large buildings made of concrete or other materials that collect and store solar heat during the day. In a phenomenon known as the “<a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2010GL042845">urban heat island</a>” effect, city centres can often be several degrees warmer than the surrounding countryside. </p>
<p>When cities are hotter, they use more energy for cooling. This usually results in more greenhouse gas emissions, due in part to the energy consumed, and contributes further to climate change. </p>
<p>New Zealand is different because our land mass has a maximum width of 400 kilometres. This means that unlike many urban islands on the African, Asian or American continents, New Zealand’s city centres benefit from the cooling effects of being near the ocean. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/climate-explained-why-some-people-still-think-climate-change-isnt-real-124763">Climate explained: why some people still think climate change isn't real</a>
</strong>
</em>
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<p>There are many <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2010GL042845">international</a> <a href="https://www.sciencedirect.com/science/article/abs/pii/S221209551530002X">studies</a> showing white roofs are effective in mitigating the urban heat island effect in densely populated cities. But there is little evidence that using white roofs in New Zealand cities could result in significant energy reductions. </p>
<p>A growing number of <a href="https://phys.org/news/2019-04-roofs-overheating-cities-heatwaves.html">studies</a> suggest making the surfaces of buildings and infrastructure more light reflecting could significantly lower extreme temperatures, particularly <a href="https://www.sciencedaily.com/releases/2019/08/190814093856.htm">during heat waves</a>, not just in cities but in rural areas as well. A <a href="https://e360.yale.edu/features/urban-heat-can-white-roofs-help-cool-the-worlds-warming-cities">recent study</a> shows strategic replacement of dark surfaces with white could lower heatwave maximum temperatures by 2°C or more, in a range of locations. </p>
<p>But studies have also identified some practical limitations and potential side effects, including the possibility of <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2011JD016281">reduced evaporation and rainfall in urban areas in drier climates</a>. </p>
<p>In conclusion, white roofs could be a good idea for New Zealand to keep homes and cities slightly cooler. As temperatures continue to rise, this could reduce the energy needed for cooling. We should consider this option more often, particularly for commercial-scale buildings made of heat-retaining materials in larger cities.</p><img src="https://counter.theconversation.com/content/128918/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dr Maibritt Pedersen Zari is a Senior Lecturer at the Wellington School of Architecture, Victoria University of Wellington.</span></em></p><p class="fine-print"><em><span>Nilesh Bakshi does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Buildings soak up the sun’s heat, but research shows that white roofs and surfaces can reduce temperatures inside, particularly during heat waves.Nilesh Bakshi, Lecturer, Te Herenga Waka — Victoria University of WellingtonMaibritt Pedersen Zari, Senior Lecturer in Sustainable Architecture, Te Herenga Waka — Victoria University of WellingtonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1288552019-12-17T19:03:27Z2019-12-17T19:03:27ZClimate explained: which countries are likely to meet their Paris Agreement targets<figure><img src="https://images.theconversation.com/files/306990/original/file-20191215-85371-9ms15f.jpg?ixlib=rb-1.1.0&rect=40%2C45%2C3794%2C1776&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">To keep temperatures from rising above 1.5℃ requires reducing fossil fuel burning by half by 2032.</span> <span class="attribution"><span class="source">from www.shutterstock.com</span></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.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">
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<p><em><strong><a href="https://theconversation.com/nz/topics/climate-explained-74664">Climate Explained</a></strong> is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.</em> </p>
<p><em>If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz</em></p>
<blockquote>
<p><strong>Which countries in the world have met or bettered their Paris Agreement targets?</strong></p>
</blockquote>
<p>The 2015 <a href="https://unfccc.int/process-and-meetings/the-paris-agreement/the-paris-agreement">Paris Agreement</a> is much more than a one-off climate change deal. Its main aim to limit global warming to well below 2°C, ideally 1.5°C, was a breakthrough. </p>
<p>A follow-up <a href="https://www.ipcc.ch/sr15/">report</a> shows that keeping warming below 1.5°C will require reducing fossil fuel burning by half by 2032. The 1.5°C target has been written into New Zealand’s <a href="https://www.mfe.govt.nz/climate-change/zero-carbon-amendment-act">Zero Carbon Act</a>. </p>
<p>But the ongoing process is also notable. Each country has registered a pledge (<a href="https://unfccc.int/process-and-meetings/the-paris-agreement/nationally-determined-contributions-ndcs">Nationally Determined Contribution</a>, or NDC) to indicate how it plans to meet the agreement’s terms. </p>
<p>Without climate action, we are heading for <a href="https://climateactiontracker.org/global/temperatures/">4.5°C of warming by 2100</a>. Current pledges, if fully realised, take us to 2.8°C.</p>
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<strong>
Read more:
<a href="https://theconversation.com/the-madrid-climate-talks-failed-spectacularly-heres-what-went-down-128921">The Madrid climate talks failed spectacularly. Here's what went down</a>
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<p>Countries have complete freedom regarding their target and how to achieve it. The NDCs will be revised every five years, first in 2020, and are required to be increasingly ambitious over time. The idea is that the international community can <a href="https://www.sciencedirect.com/science/article/pii/S030142151830750X">check the targets</a> against performance and global goals. Best practice can be shared, and poor performance exposed.</p>
<p>This flexibility made it possible to get the agreement through, but it can be confusing. Targets have been set for different dates, from different baselines and for different types of emissions. </p>
<p>Countries may have good reasons for setting weaker targets – they may be starting from a low base, like <a href="https://www.sciencedirect.com/science/article/pii/S030142151830750X">India</a>. Or they may have unusual emissions, like New Zealand’s <a href="https://www.mfe.govt.nz/climate-change/state-of-our-atmosphere-and-climate/new-zealands-greenhouse-gas-inventory">large proportion of agricultural methane</a>.</p>
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<strong>
Read more:
<a href="https://theconversation.com/climate-explained-what-each-of-us-can-do-to-reduce-our-carbon-footprint-123851">Climate explained: what each of us can do to reduce our carbon footprint</a>
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<p>So for each country we can ask:</p>
<ol>
<li>Does the target really reflect its highest level of ambition, as agreed in Paris?</li>
<li>Is it consistent with 2°C or 1.5°C of global warming?</li>
<li>Is it on track to meet its target?</li>
<li>Will it ratchet up its ambition in 2020?</li>
</ol>
<p>Let’s look at two large emitters, the EU and US, together responsible for <a href="https://ourworldindata.org/co2-and-other-greenhouse-gas-emissions">47% of historic, and 24% of current</a>, emissions.</p>
<p><strong><a href="https://unfccc.int/sites/default/files/adpeu.pdf">EU 2030 target</a>: 40% reduction from 1990 levels</strong></p>
<p>The European Union is on track for a <a href="https://climateactiontracker.org/countries/eu/">48% reduction</a>, partly due to a collapse of heavy industry in Eastern Europe in the 1990s and more recently from a phase-out of coal. Despite this, because of lack of action on transport and buildings, and an increasing reliance on natural gas, the EU has been <a href="https://climateactiontracker.org/countries/eu/2019-01-03/fair-share/">rated insufficient</a> by <a href="https://climateactiontracker.org/">Climate Action Tracker</a>, an independent research unit founded in 2009 and partly funded by the German Ministry for Environment. </p>
<p>Last week, the new president of the European Commission, Ursula von der Leyen, announced plans for the EU to <a href="https://www.euronews.com/2019/12/11/european-green-deal-eu-chief-von-der-leyen-to-unveil-measures-to-tackle-climate-emergency">increase the target up to a 55% reduction</a>, along with sweeping implementation plans. Some European countries are moving faster: Denmark, already <a href="https://dce2.au.dk/pub/SR318.pdf">down 32%</a> on 1990 levels, has this month <a href="https://www.bloomberg.com/news/articles/2019-12-07/denmark-strikes-deal-to-slash-co2-emissions-by-70-in-a-decade">legislated a 70% reduction by 2030</a>.</p>
<p><strong><a href="https://www4.unfccc.int/sites/ndcstaging/PublishedDocuments/United%20States%20of%20America%20First/U.S.A.%20First%20NDC%20Submission.pdf">US 2025 target</a>: 26% reduction from 2005 levels</strong></p>
<p>So far the US is down <a href="https://climateactiontracker.org/countries/usa/">11%</a>. The <a href="https://unfccc.int/files/focus/long-term_strategies/application/pdf/mid_century_strategy_report-final_red.pdf">Obama-era climate plan</a> would have achieved the 2025 target, but is now being rolled back, and the US will <a href="https://en.wikipedia.org/wiki/United_States_withdrawal_from_the_Paris_Agreement">leave</a> the Paris Agreement on November 4 next year, the day after the elections. </p>
<p>On the other hand, city and state-level <a href="https://www.c2es.org/document/greenhouse-gas-emissions-targets/">actions</a> and the continued <a href="https://www.renewableenergyworld.com/2019/08/07/forecast-shows-continued-decline-for-coal">decline of coal</a> mean some further reductions in emissions are likely.</p>
<p>Now let’s consider two rapidly growing emitters, China and India, responsible for <a href="https://ourworldindata.org/co2-and-other-greenhouse-gas-emissions">16% of historic and 33% of current</a> emissions.</p>
<p><strong><a href="https://www4.unfccc.int/sites/ndcstaging/PublishedDocuments/China%20First/China%27s%20First%20NDC%20Submission.pdf">China target</a>: peak emissions by 2030</strong></p>
<p>China is <a href="https://www.nature.com/articles/s41467-019-09159-0">well on track</a> to achieve this. Emissions actually levelled off for five years before <a href="https://climateactiontracker.org/countries/china/">rising again in 2018</a>. China is the world’s largest installer of renewable energy, but also the world’s largest consumer of coal. It also funds a lot of coal power stations in other countries. China has announced it will greatly <a href="https://www.reuters.com/article/us-france-china-climatechange/china-to-cap-rising-emissions-by-2030-in-boost-to-paris-u-n-deal-idUSKCN0PA1G420150630">strengthen its target next year</a>.</p>
<p><strong><a href="https://www4.unfccc.int/sites/ndcstaging/PublishedDocuments/India%20First/INDIA%20INDC%20TO%20UNFCCC.pdf">India’s 2030 target</a>: reduce emissions intensity relative to GDP to 33% below 2005 levels</strong></p>
<p>India is <a href="https://climateactiontracker.org/countries/india/">well on track</a> to meet this, having rapidly moved into <a href="https://mnre.gov.in/physical-progress-achievements">solar energy</a>. Its target involves an increase in total emissions, but should be seen in light of India’s <a href="https://en.wikipedia.org/wiki/List_of_countries_by_greenhouse_gas_emissions_per_capita">very low emissions</a> of only two tonnes of carbon dioxide per capita. This is compatible with the 2°C target.</p>
<p><strong><a href="https://www4.unfccc.int/sites/ndcstaging/PublishedDocuments/Australia%20First/Australias%20Intended%20Nationally%20Determined%20Contribution%20to%20a%20new%20Climate%20Change%20Agreement%20-%20August%202015.pdf">Australia 2030 target</a>: 26% below 2005 levels</strong></p>
<p>Australia is presently only on track for a 7% reduction. But a decrease in forest clearance has masked the fact that emissions from fossil fuel burning have increased and are projected to increase further, to <a href="https://climateactiontracker.org/countries/australia/">8% above 2005 levels by 2030</a>. </p>
<p>Australia has become the world’s <a href="https://www.tai.org.au/sites/default/files/P667%20High%20Carbon%20from%20a%20Land%20Down%20Under%20%5BWEB%5D.pdf">third-largest exporter</a> of fossil fuels, behind Russia and Saudi Arabia. On the other hand, many state governments have set ambitious targets and made either aspirational or legal <a href="https://climateactiontracker.org/countries/australia/">commitments toward zero emissions</a>. </p>
<p><strong><a href="https://www4.unfccc.int/sites/ndcstaging/PublishedDocuments/New%20Zealand%20First/New%20Zealand%20first%20NDC.pdf">New Zealand 2030 target</a>: 30% below 2005 levels</strong> </p>
<p>New Zealand is <a href="https://www.mfe.govt.nz/climate-change/emissions-reduction-targets/our-targets-and-emissions-projections">projected</a> to reduce by 15% under current policies, with the difference to be made up by purchasing carbon units from overseas. This may set up a clash with the <a href="https://www.mfe.govt.nz/climate-change/zero-carbon-amendment-act">Zero Carbon Act</a>, which requires that “emissions budgets must be met, as far as possible, through domestic emissions reductions and domestic removals.” However, these figures mask the fact New Zealand is, most unusually, using “gross-net” accounting. The 2030 target is for net emissions (that is, including the carbon sink of forests), but is measured against their 2005 gross emissions. The target allows net emissions to grow by up to 24% and is <a href="https://climateactiontracker.org/countries/new-zealand/">woefully unambitious</a>.</p>
<p>Using a different methodology, taking into account each country’s situation, performance, and plans, the <a href="https://www.climate-change-performance-index.org/">Climate Change Performance Index</a> found that the top three countries are Sweden, Denmark and Morocco, and the bottom three are Taiwan, Saudi Arabia and the US. New Zealand is ranked 34th and Australia 53rd of the 58 countries assessed.</p><img src="https://counter.theconversation.com/content/128855/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Robert McLachlan does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Under the Paris Agreement, countries have registered plans to meet emissions reductions, but the current pledges, if fully realised, would take us to 2°C by the 2050s.Robert McLachlan, Professor in Applied Mathematics, Massey UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1281062019-12-03T18:35:43Z2019-12-03T18:35:43ZClimate explained: how climate change will affect food production and security<figure><img src="https://images.theconversation.com/files/304808/original/file-20191202-66998-1nvmtz1.jpg?ixlib=rb-1.1.0&rect=127%2C179%2C4857%2C3138&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Many temperate crops require winter chilling to initiate flowering or fruit ripening, and orchards may need to shift to colder areas.</span> <span class="attribution"><span class="source">from www.shutterstock.com</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.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">
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<p><em><strong><a href="https://theconversation.com/nz/topics/climate-explained-74664">Climate Explained</a></strong> is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.</em> </p>
<p><em>If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz</em></p>
<blockquote>
<p><strong>According to the United Nations, food shortages are a threat due to climate change. Are food shortages a major threat to New Zealand due to climate change?</strong></p>
</blockquote>
<p>Climate change is altering conditions that sustain food production, with cascading consequences for food security and global economies. <a href="https://advances.sciencemag.org/content/5/11/eaaw9976">Recent research</a> evaluated the simultaneous impacts of climate change on agriculture and marine fisheries globally. </p>
<p>Modelling of those impacts under a business-as-usual carbon emission scenario suggested about 90% of the world’s population – most of whom live in the least developed countries – will experience reductions in food production this century.</p>
<p>New Zealanders are fortunate to live in a part of the world blessed with relatively fertile soils, adequate water supplies and mild temperatures. This gives us a comparative advantage for agriculture and horticulture over many other countries, including our main trading partner, Australia.</p>
<p>New Zealand produces more than enough food for its population. Exports exceed local consumption, and climate-change induced food shortages should not be an imminent risk for New Zealand. But behind every general statement like this lies some rather more troubling detail. </p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/feeding-the-world-archaeology-can-help-us-learn-from-history-to-build-a-sustainable-future-for-food-117601">Feeding the world: archaeology can help us learn from history to build a sustainable future for food</a>
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<h2>Overcoming domestic challenges</h2>
<p>As residents of a developed country, we are accustomed to accessing the world’s resources through supermarkets. New Zealanders take for granted that most foods (even those we do not produce, like rice or bananas) will be available all year round. </p>
<p>Asparagus, new potatoes and strawberries are examples of foods New Zealanders may expect to see only at particular times of the year, but if apples or kiwifruit are out of stock, people usually complain. Our expectations are based on imports of products when they are out of season in New Zealand. The availability of those imports may be seriously compromised by climate change.</p>
<p>A recent <a href="https://www.mfe.govt.nz/sites/default/files/media/Climate%20Change/Climate-change-projections-2nd-edition-final.pdf">Ministry for the Environment report</a> describes climate impacts, including detailed projections of the average temperature increase and changes in rainfall patterns across New Zealand. The consistent trends are towards wetter conditions in the west, drier in the east and the largest average temperature rises in the north.</p>
<p><a href="https://www.mfe.govt.nz/sites/default/files/impacts-agriculture-sep01.pdf">Implications for agriculture</a> are manifold. For example, many temperate crops require cool autumn or winter temperatures to initiate flowering or fruit ripening. Orchards may need to be relocated further south, or novel <a href="https://www.washingtonpost.com/lifestyle/home/climate-change-is-already-hurting-fruit-breeders-and-consumers-could-soon-feel-the-pain/2019/03/27/6d5252fa-36c2-11e9-854a-7a14d7fec96a_story.html">low-chill varieties</a> may need to be bred, as is already happening around the world.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/climate-explained-regenerative-farming-can-help-grow-food-with-less-impact-123090">Climate explained: regenerative farming can help grow food with less impact</a>
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<p>Insect pests and diseases are normally controlled by our low winter temperatures, but they may become more of a problem in the future. <a href="https://www.nzherald.co.nz/the-country/news/article.cfm?c_id=16&objectid=11993587">Introduced pests and diseases</a> include fruit flies that have a major impact in Australia and other more tropical countries, but struggle to establish breeding colonies in New Zealand. Strong biosecurity controls are our best bet for reducing this risk.</p>
<p>What matters more than the gradual increase in temperature predicted by climate change models, is the greater frequency of extreme weather events. These include droughts, floods and hail, which can lead to total crop losses in particular regions. One obvious mitigation strategy is to expand the provision of irrigation in our drier eastern regions, but concerns over water quality in our rivers mean this is not a popular option with the public – for example on the <a href="http://docs.niwa.co.nz/library/public/DraPNHerev3.pdf">Heretaunga Plains</a> or in <a href="https://www.agscience.org.nz/water-in-canterbury-our-vital-resource/">Canterbury</a>.</p>
<h2>Risks to imported products</h2>
<p>New Zealand is a net exporter of dairy, beef, lamb and many fruit and vegetables, but for some products, we depend heavily on imports. <a href="https://www.indexmundi.com/agriculture/?country=nz">Figures from the US Department of Agriculture</a> are not perfect, but they highlight trade imbalances for major commodities. </p>
<p>New Zealand imports all rice and most of its wheat. It is a net importer of pork products. Horticultural data released annually in <a href="https://www.freshfacts.co.nz/files/freshfacts-2018.pdf">Fresh Facts</a> show New Zealand’s major horticultural imports are (in order of value) wine, nuts, processed vegetables, coffee, bananas and table grapes. These imported products come primarily from Australia, China, the US and Ecuador – all countries that may be less <a href="http://www.fao.org/3/a-i6030e.pdf">resilient to climate change</a> than New Zealand. </p>
<p>As a <a href="http://www.fao.org/3/a-i6030e.pdf">recent report</a> by the UN Food and Agriculture Organisation (<a href="http://www.fao.org/home/en/">FAO</a>) explains, rising temperatures, rising seas and the increasing frequency of adverse weather events will interact to reduce agricultural and horticultural productivity in many regions around the world. While New Zealand is unlikely to experience food shortages in the near future as a direct result of climate change, the price and availability of imported products may increase significantly.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/feeding-cities-in-the-21st-century-why-urban-fringe-farming-is-vital-for-food-resilience-106162">Feeding cities in the 21st century: why urban-fringe farming is vital for food resilience</a>
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<h2>Food poverty</h2>
<p>Unfortunately, there is another important consideration. Some New Zealanders already experience food insecurity. The 2008/9 <a href="https://www.health.govt.nz/publication/focus-nutrition-key-findings-2008-09-nz-adult-nutrition-survey">Adult Nutrition Survey</a> found 14% of New Zealand households reported running out of food often or sometimes due to lack of money. </p>
<p>Perhaps rather than worrying about the future impact of climate change on the price or availability of imported rice or bananas, we should be paying more attention to this social inequity. </p>
<p>As a wealthy agricultural nation and a net exporter of food, it does not seem right that one sector of our society is already regularly experiencing food shortages.</p><img src="https://counter.theconversation.com/content/128106/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Prof Julian Heyes is employed by Massey University and has received MBIE funding for research that supports horticultural export industries. He also acts as an NZ Aid consultant supporting horticultural development in North Lombok, Indonesia. He is a Life Member of the New Zealand Society of Plant Biologists and Vice President ot the New Zealand Institute for Agricultural and Horticultural Science, a professional body that supports agricultural and horticultural scientists. </span></em></p>New Zealand is a net exporter of many fruit and vegetables. While climate-change induced food shortages are not an imminent risk, some crops may be affected by rising temperatures and extreme weather.Julian Heyes, Head of School of Food and Advanced Technology@ISHS_CMFV, Massey UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1277072019-11-26T18:40:48Z2019-11-26T18:40:48ZClimate explained: how much does flying contribute to climate change?<figure><img src="https://images.theconversation.com/files/303372/original/file-20191125-74588-1iuh45l.jpg?ixlib=rb-1.1.0&rect=62%2C413%2C5892%2C3511&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Planes can create clouds of tiny ice crystals, called contrails, and some studies suggest they could have an a significant effect on climate.</span> <span class="attribution"><span class="source">from www.shutterstock.com</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.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">
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<p><em><strong><a href="https://theconversation.com/nz/topics/climate-explained-74664">Climate Explained</a></strong> is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.</em> </p>
<p><em>If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz</em></p>
<blockquote>
<p><strong>How much does our use of air travel contribute to the problem of climate change? And is it more damaging that it is being created higher in our atmosphere?</strong></p>
</blockquote>
<p>The <a href="https://www.bbc.com/future/article/20190909-why-flight-shame-is-making-people-swap-planes-for-trains">flight shaming movement</a> has raised our awareness of air travel’s contribution to climate change. With all the discussion, you might be surprised to learn that air travel globally <a href="https://www.ipcc.ch/site/assets/uploads/2018/02/ipcc_wg3_ar5_chapter8.pdf">only accounts for about 3% of the warming</a> human activities are causing. Why all the fuss?</p>
<p>Before I explain, I should come clean. I am writing this on the train from Christchurch to Kaikoura, where I will give a talk about my recent book <a href="https://www.bwb.co.nz/books/hashtag-no-fly">#NoFly: walking the talk on climate change</a>. I have some skin in this game.</p>
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Read more:
<a href="https://theconversation.com/flight-shame-flying-less-plays-a-small-but-positive-part-in-tackling-climate-change-125440">Flight shame: flying less plays a small but positive part in tackling climate change</a>
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<h2>Staying grounded</h2>
<p>Taking a train around New Zealand is no mean feat. In the North Island, the <a href="https://www.greatjourneysofnz.co.nz/northern-explorer/">train between Auckland and Wellington</a> runs only every second day. If you get off at a stop along the way, you have to wait another two days to continue your journey. You can catch a bus, but you’ll spend that bus journey fantasising about the possibility of an overnight train service.</p>
<p>So why do it? A good deal of global carbon emissions come from <a href="https://www.epa.gov/ghgemissions/sources-greenhouse-gas-emissions">industrial processes or electricity generation</a> under the control of governments and corporations, rather than individual citizens. For many of us, a decision not to fly might be the most significant reduction in emissions we can make as individuals.</p>
<p>As Swedish climate activist Greta Thunberg has shown, <a href="https://www.bbc.com/news/science-environment-49349566">refusing to fly</a> also sends a powerful signal to others, by showing that you are willing to change your own behaviour. Politicians and corporate sales departments will take note if we start acting together. </p>
<h2>Impacts of aviation</h2>
<p>Aviation affects the climate in a <a href="https://books.google.co.nz/books?id=LIvEZkURpcMC&lpg=PR11&ots=VFhTKL5oG-&dq=aviation%20and%20climate%20change&lr&pg=PR10#v=onepage&q=aviation%20and%20climate%20change&f=false">variety of ways</a>. </p>
<p>Because any carbon dioxide you emit stays in the atmosphere for hundreds of years, it doesn’t matter much whether you release it from the exhaust pipe of your car at sea level or from a jet engine several kilometres high. Per passenger, a flight from Auckland to Wellington will put a similar amount of carbon dioxide into the air as driving solo in your car. Catching the train will <a href="https://calculator.toitu.co.nz/?calculator=travel">cut your carbon emissions seven-fold</a>.</p>
<p>When aircraft burn jet fuel, however, they also emit short-lived gases like nitrogen oxides, which can react with other gases in the air within a day of being released. When nitrogen oxides are released at altitude they can react with oxygen to put more ozone into the air, but can also remove methane. </p>
<p>Ozone and methane are both greenhouse gases, so this chain of chemical reactions can lead to both heating and cooling effects. Unfortunately the net result when these processes are added together is to <a href="https://www.repository.cam.ac.uk/bitstream/handle/1810/263217/Dessens_TransPol_2014_accepted.pdf?sequence=1">drive more warming</a>.</p>
<p>Depending on the atmospheric conditions, aircraft can also create <a href="https://science-edu.larc.nasa.gov/contrail-edu/science.html">contrails</a>: clouds of tiny ice crystals. The science is not as clear cut on how contrails influence the climate, but <a href="https://www.atmos-chem-phys.net/19/8163/2019/">some studies suggest</a> they could have an effect as significant as the carbon dioxide released during a flight. </p>
<p>There is also considerable uncertainty as to whether aircraft exhaust might affect cloud formation itself - this could be a further <a href="https://agupubs.onlinelibrary.wiley.com/doi/10.1002/2014JD021914">significant contribution to warming</a>.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/climate-explained-why-dont-we-have-electric-aircraft-123910">Climate explained: why don't we have electric aircraft?</a>
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<h2>Growing demand for air travel</h2>
<p>Offsetting, by planting trees or restoring natural wildlands, will take carbon dioxide back out of the atmosphere. But we would have to do this on a massive scale to feed our appetite for flight. </p>
<p>Emissions from international air travel are not included in the <a href="https://unfccc.int/process-and-meetings/the-paris-agreement/the-paris-agreement">Paris Agreement</a>, although the United Nations has been working on the Carbon Offsetting and Reduction Scheme for International Aviation (<a href="https://www.icao.int/environmental-protection/CORSIA/Pages/default.aspx">CORSIA</a>), which may begin to deal with these. Initially, the scheme will be voluntary. Airlines flying routes between countries that join the scheme will have to offset any emissions above 2020 levels from January 2021. </p>
<p>Emissions from flying <a href="https://www.icao.int/Meetings/a38/Documents/WP/wp026_en.pdf">stand to triple by 2050</a> if demand for air travel continues to grow. Even if air travel became carbon neutral through the use of biofuels or electric planes, the effects from contrails and interactions with clouds mean that flying may never be climate neutral. </p>
<p>With no easy fixes on the horizon, many people are thinking hard about their need to fly. This is why I <a href="https://theconversation.com/costly-signals-needed-to-deliver-inconvenient-truth-82380">took a year off air travel</a> (alongside my colleague Quentin Atkinson) in 2018. </p>
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Read more:
<a href="https://theconversation.com/costly-signals-needed-to-deliver-inconvenient-truth-82380">Costly signals needed to deliver inconvenient truth</a>
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<p>I have been back on planes in 2019, but I have learned how to reduce my flying, by combining trips and making better use of video conferencing. </p>
<p>Fly if you must, offset if you can, but – if you are concerned about climate change – one of the best things you could choose to do is to fly less.</p><img src="https://counter.theconversation.com/content/127707/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Shaun Hendy is on the Council of the New Zealand Association of Scientists and is author of the book #NoFly, published by Bridget Williams Books in October 2019. </span></em></p>Globally, emissions from air travel account for only about 3% of the warming human activities are causing, but aviation affects our climate in a number of ways.Shaun Hendy, Professor of Physics, University of Auckland, Waipapa Taumata RauLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1272022019-11-19T19:20:31Z2019-11-19T19:20:31ZClimate explained: why coastal floods are becoming more frequent as seas rise<figure><img src="https://images.theconversation.com/files/302297/original/file-20191118-66917-mzy9ny.jpg?ixlib=rb-1.1.0&rect=36%2C207%2C5970%2C3494&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">As sea levels rise, it becomes easier for ocean waves to spill further onto land.</span> <span class="attribution"><span class="source">from www.shutterstock.com</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.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">
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<p><em><strong><a href="https://theconversation.com/nz/topics/climate-explained-74664">Climate Explained</a></strong> is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.</em> </p>
<p><em>If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz</em></p>
<blockquote>
<p><strong>I saw an article claiming that “king tides” will increase in frequency as sea level rises. I am sceptical. What is the physics behind such a claim and how is it related to climate change? My understanding is that a king tide is a purely tidal effect, related to Moon, Sun and Earth axis tilt, and is quite different from a storm surge.</strong></p>
</blockquote>
<p>This is a good question, and you are right about the tides themselves. The twice-daily tides are caused by the gravitational forces of the Moon and the Sun, and the rotation of the Earth, none of which is changing. </p>
<p>A “king” tide occurs around the time when the Moon is at its closest to the Earth and Earth is at its closest to the Sun, and the <a href="https://oceanservice.noaa.gov/facts/kingtide.html">combined gravitational effects are strongest</a>. They are the highest of the high tides we experience.</p>
<p>But the <a href="https://www.stuff.co.nz/environment/climate-news/115526777/little-shoal-bay-rising-sea-levels-and-storm-surges-cause-flooding-on-aucklands-north-shore">article</a> you refer to was not really talking about king tides. It was discussing coastal inundation events. </p>
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Read more:
<a href="https://theconversation.com/king-tides-and-rising-seas-are-predictable-and-were-not-doing-enough-about-it-91318">King tides and rising seas are predictable, and we're not doing enough about it</a>
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<h2>When tides, storms and sea levels combine</h2>
<p>During a king tide, houses and roads close to the coast can be flooded. The article referred to the effects of coastal flooding generally, using “king tide” as a shorthand expression. We know that king tides are not increasing in frequency, but we also know that coastal flooding and <a href="https://www.mfe.govt.nz/publications/climate-change/preparing-coastal-change-summary-of-coastal-hazards-and-climate-change">coastal erosion events are happening more frequently</a>. </p>
<p>As sea levels rise, it becomes easier for ocean waves to penetrate on to the shore. The biggest problem arises when storms combine with a high tide, and ride on top of higher sea levels. </p>
<p>The low air pressure near the centre of a storm pulls up the sea surface below. Then, onshore winds can pile water up against the coast, allowing waves to run further inshore. Add a high or king tide and the waves can come yet further inshore. Add a bit of sea level rise and the waves penetrate even further.</p>
<p>The background sea level rise has been only <a href="https://www.mfe.govt.nz/publications/climate-change/preparing-coastal-change-summary-of-coastal-hazards-and-climate-change">20cm around New Zealand’s coasts</a> so far, but even that makes a noticeable difference. An apparently small rise in overall sea level allows waves generated by a storm to come on shore much more easily. Coastal engineers use the rule of thumb that <a href="https://www.pce.parliament.nz/publications/preparing-new-zealand-for-rising-seas-certainty-and-uncertainty">every 10cm of sea level rise increases the frequency of a given coastal flood by a factor of three</a>.</p>
<p>This means that 10cm of sea level rise will turn a one-in-100-year coastal flood into a one-in-33-year event. With another 10cm of sea level rise, it becomes a one-in-11-year event, and so on.</p>
<h2>Retreating from the coast</h2>
<p>The occurrence rates change so quickly because in most places, beaches are fairly flat. A 10cm rise in sea levels might translate to 30 or 40 metres of inland movement of the high tide line, depending on the slope of the beach. So when the tide is high and the waves are rolling in, the sea can come inland tens of metres further than it used to, unless something like a coastal cliff or a sea wall blocks its way. </p>
<p>The worry is that beaches are likely to remain fairly flat, so anything within 40 metres of the current high tide mark is likely to be eroded away as storms occur and we experience another 10cm of sea level rise. If a road or a house is on an erodible coast (such as a line of sand dunes), it is not the height above sea level that matters but the distance from the high tide mark.</p>
<p>Another 30cm of sea level rise is already “baked in”, <a href="https://www.mfe.govt.nz/publications/climate-change/preparing-coastal-change-summary-of-coastal-hazards-and-climate-change">guaranteed over the next 40 years</a>, regardless of what happens with greenhouse gas emissions and action on climate change. By the end of the century, <a href="https://www.mfe.govt.nz/publications/climate-change/preparing-coastal-change-summary-of-coastal-hazards-and-climate-change">at least another 20cm</a> on top of that is virtually certain.</p>
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<strong>
Read more:
<a href="https://theconversation.com/our-shameful-legacy-just-15-years-worth-of-emissions-will-raise-sea-level-in-2300-126429">Our shameful legacy: just 15 years' worth of emissions will raise sea level in 2300</a>
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<p>The 30cm rise multiplies the chances of coastal flooding by a factor of around 27 (3x3x3) and 50cm by the end of the century increases coastal flooding frequency by a factor of around 250. That would make the one-in-100-year coastal flood likely every few months, and roads, properties and all kinds of built infrastructure within 200 metres of the current coastline would be vulnerable to inundation and damage. </p>
<p>These are round numbers, and local changes depend on coastal shape and composition, but they give the sense of how quickly things can change. Already, key roads in Auckland (such as Tamaki Drive) are <a href="https://www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=11864665">inundated when storms combine with high tides</a>. Such events are set to become much more common as sea levels continue to rise, to the point where they will become part of the background state of the coastal zone. </p>
<p>To ensure cities such as Auckland (and others around the world) are resilient to such challenges, we’ll need to retreat from the coast where possible (move dwellings and roads inland) and to build coastal defences where that makes sense. The coast is coming inland, and we need to move with it.</p><img src="https://counter.theconversation.com/content/127202/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>James Renwick receives funding from the Marsden Fund and from the NZ Ministry for Business, Innovation and Employment to study climate variability and change. He is affiliated with Ekos (ekos.org.nz) and the TrackZero Trust (<a href="http://www.trackzero.nz">www.trackzero.nz</a>) as a Board member of both organisations. He is also a member of the Green Party of NZ.</span></em></p>For every ten centimetres of sea level rise, the chances of a 100-year coastal flood increase three-fold. This means we’ll have to build flood defenses or retreat from the coast.James Renwick, Professor, Physical Geography (climate science), Te Herenga Waka — Victoria University of WellingtonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1266712019-11-12T19:02:47Z2019-11-12T19:02:47ZClimate explained: how growth in population and consumption drives planetary change<figure><img src="https://images.theconversation.com/files/301157/original/file-20191111-178525-ht8l9a.jpg?ixlib=rb-1.1.0&rect=98%2C117%2C4263%2C2785&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Rapid population growth and increased consumption are now seen as the main drivers of environmental changes.</span> <span class="attribution"><span class="source">from www.shutterstock.com</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.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">
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<p><em><strong><a href="https://theconversation.com/nz/topics/climate-explained-74664">Climate Explained</a></strong> is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.</em> </p>
<p><em>If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz</em></p>
<blockquote>
<p><strong>The growth of the human population over the last 70 years has exploded from 2 billion to nearly 8 billion, with a compounding net growth of over 30,000 per day. We all breathe out carbon dioxide with every breath. That equates to about 140 billion CO₂ breaths every minute. Isn’t it logical that atmospheric carbon will continue to increase with the birth rate regardless of what we do about fossil fuel reduction?</strong></p>
</blockquote>
<p>This question touches on the core of our impact on planetary change. It highlights the exponential growth in the human population, but also homes in on the potential direct input of carbon dioxide from humans, through respiration. </p>
<p>As I explain in more detail below, our breathing does not contribute to the net accumulation of carbon dioxide in the atmosphere. But population growth, combined with an increase in consumption, is now seen as the <a href="https://www.stockholmresilience.org/research/research-news/2015-01-15-new-planetary-dashboard-shows-increasing-human-impact.html">main driver of change in the Earth system</a>. </p>
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Read more:
<a href="https://theconversation.com/climate-explained-why-your-backyard-lawn-doesnt-help-reduce-carbon-dioxide-in-the-atmosphere-122312">Climate explained: why your backyard lawn doesn't help reduce carbon dioxide in the atmosphere</a>
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<h2>Humans: a moment in geological time</h2>
<p>Earth has been around for 4.56 billion years. The <a href="https://www.livescience.com/1804-greatest-mysteries-life-arise-earth.html">earliest evidence for life on Earth</a> comes from fossilised mats of cyanobacteria that are about 3.7 billion years old. </p>
<p>From around 700 million years ago, and certainly from 540 million years ago, life exploded into its present myriad forms, from molluscs to lung fish, reptiles, insects, plants, fishes and mammals – culminating in hominids and finally <em>Homo sapiens</em>. Genetic studies suggest <a href="https://www.nature.com/scitable/knowledge/library/overview-of-hominin-evolution-89010983/">hominids evolved from primates around 6 million years ago</a>, with the oldest hominid fossil dating from 4.4 million years ago in East Africa. </p>
<p>Our species appeared around 200,000 to 300,000 years ago, a blink of an eye in geological terms. From Africa, <em>Homo sapiens</em> migrated through Europe and Asia and spread across the world, at lightning speeds. </p>
<p>Part of the question is about a putative link between human biological functions and climate. <em>Homo sapiens</em> is <a href="https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.1001127">one of more than 28 million living species today</a>, and some <a href="https://link.springer.com/chapter/10.1007/978-94-011-5874-9_7">35 billion species that have ever lived on Earth</a>. There has always been a link between life and Earth’s atmosphere, and perhaps the clearest indicator is oxygen. </p>
<h2>Life, carbon and climate</h2>
<p>Cyanobacteria were the first organisms to master photosynthesis and <a href="https://www.pnas.org/content/96/20/10955">began adding oxygen to Earth’s early atmosphere</a>, producing levels of 2% by 1 billion years ago. Today oxygen levels are at 20%. </p>
<p>While people inhale oxygen and exhale carbon dioxide (billions of tonnes each year), this does <a href="https://slate.com/news-and-politics/2009/08/are-you-heating-the-planet-when-you-breathe.html">not represent new carbon in the atmosphere</a>, but rather recycled carbon that had been taken up by the animals and plants we eat. Furthermore, the hard parts of human skeletons are potential carbon stores, if buried sufficiently deep. </p>
<p>There is a constant cycling of carbon between geological, oceanographic and biological processes. <em>Homo sapiens</em> is part of this carbon cycle that plays out at the Earth’s surface. Like all living organisms, we derive the carbon we need from our immediate environment and give it up again through breathing, living and dying. </p>
<p>Carbon is only added to the atmosphere if it is taken out of long-term geological stores such as carbon-rich sediments, oil, natural gas and coal.</p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/climate-explained-why-carbon-dioxide-has-such-outsized-influence-on-earths-climate-123064">Climate explained: why carbon dioxide has such outsized influence on Earth's climate</a>
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<h2>Planetary impact of humans</h2>
<p>But the <a href="https://ourworldindata.org/world-population-growth">remarkable growth in human population</a> is surely the critical issue. Ten thousand years ago, there were 1 million people on Earth. By 1800, there were 1 billion, 3 billion by 1960 and almost 8 billion today.</p>
<p>When these figures are plotted on a graph, the growth line looks almost vertical from the 1800s onwards. <a href="https://www.pewresearch.org/fact-tank/2019/06/17/worlds-population-is-projected-to-nearly-stop-growing-by-the-end-of-the-century/">Population growth may eventually flatten out</a>, but only at around 10-11 billion. </p>
<p>Alongside the unprecedented population growth of humans has been the <a href="https://www.ipbes.net/news/million-threatened-species-thirteen-questions-answers">loss of many non-human species</a> (10,000 extinctions per million populations per year, or <a href="https://www.theguardian.com/environment/2018/oct/30/humanity-wiped-out-animals-since-1970-major-report-finds">60% of animal populations since 1970</a>), the rapid loss of wilderness habitat and consequent growth in farmed land, over-fishing (with up to <a href="http://blogs.edf.org/edfish/2012/07/11/fao-reports-87-of-the-worlds-fisheries-are-overexploited-or-fully-exploited/">87% of fisheries fully exploited</a>), and a staggering growth in global car numbers (from zero in the 1920s to 1 billion in 2013 and a projected <a href="https://www.weforum.org/agenda/2016/04/the-number-of-cars-worldwide-is-set-to-double-by-2040">2 billion by 2040</a>).</p>
<p>The <a href="https://www.usgs.gov/centers/nmic/copper-statistics-and-information">world production of copper</a> is an instructive proxy for human global impacts. As with many commodity curves, the trend from 1900, and particularly from the 1950s, is exponential. In 1900 around half-a-million tonnes of copper was produced worldwide. Today it is 18 million tonnes per year, with no sign of lowering consumption rates. Copper is the feedstock for much of modern-day and future green technologies. </p>
<p>Most parts of the world now experience material consumption as never before. But serious inequality remains, with over <a href="https://www.worldbank.org/en/news/press-release/2018/10/17/nearly-half-the-world-lives-on-less-than-550-a-day">3 billion living on less than US$5.50 a day</a>, and a <a href="https://www.oxfam.org/en/press-releases/just-8-men-own-same-wealth-half-world">tiny percentage who own so much</a>. </p>
<p>Some argue that it is not the numbers of people on Earth that count, but rather the way we consume and share. Whatever the politics and economics, the gross consumption level of billions of humans is, surely, the main cause of planetary change, especially since 1950. Present-day atmospheric levels of carbon dioxide are one of many symptoms of human impact.</p><img src="https://counter.theconversation.com/content/126671/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Michael Petterson has received funding for research and international development programmes during his career.</span></em></p>Discussions about climate change often skirt around the issue of population growth, but it is the main driver of rising carbon dioxide levels and many other environmental changes on a planetary scale.Michael Petterson, Professor of Geology, Auckland University of TechnologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1263372019-11-05T18:57:38Z2019-11-05T18:57:38ZClimate explained: why Mars is cold despite an atmosphere of mostly carbon dioxide<figure><img src="https://images.theconversation.com/files/299990/original/file-20191103-88414-1awmtug.jpg?ixlib=rb-1.1.0&rect=30%2C43%2C2845%2C1521&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The atmosphere of Mars is thin and very dry.</span> <span class="attribution"><a class="source" href="https://www.nasa.gov/sites/default/files/thumbnails/image/pia22511.jpg">NASA's Mars Reconnaissance Orbiter</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/287622/original/file-20190811-144878-bvgm9l.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">
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<span class="attribution"><a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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<p><em><strong><a href="https://theconversation.com/nz/topics/climate-explained-74664">Climate Explained</a></strong> is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.</em> </p>
<p><em>If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz</em></p>
<blockquote>
<p><strong>If tiny concentrations of carbon dioxide can hold enough heat to create a global warming impact on Earth, why is Mars cold? Its atmosphere is 95% carbon dioxide.</strong></p>
</blockquote>
<p>The recipe for the temperature of a planet’s surface has four major ingredients: atmospheric composition, atmospheric density, water content (from oceans, rivers and air humidity) and distance from the Sun. There are other ingredients, including seasonal effects or the presence of a magnetosphere, but these work more like adding flavour to a cake.</p>
<p>When we look at Earth, the balance of these ingredients makes our planet habitable. Changes in this balance can result in effects that can be felt on a planetary scale. This is exactly what is happening with the increase of greenhouse gases in the atmosphere of our planet. </p>
<p>Increased concentrations of carbon dioxide, methane, sulphur hexafluoride and other gases in the atmosphere have been raising the temperature of our planet’s surface gradually and will continue to do so for many years to come.</p>
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<strong>
Read more:
<a href="https://theconversation.com/climate-explained-why-carbon-dioxide-has-such-outsized-influence-on-earths-climate-123064">Climate explained: why carbon dioxide has such outsized influence on Earth's climate</a>
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<p>As a consequence, places covered in ice start melting and extreme weather events become more frequent. This poses a growing challenge for us to adapt to this new reality. </p>
<h2>Small concentration, big effect</h2>
<p>It is surprising to realise how little the concentration of carbon dioxide (CO₂) and other greenhouse gases has to change to cause such a shift in our climate. Since the 1950s, we have raised CO₂ levels in the atmosphere by a fraction of a percent, but this is already causing <a href="https://climate.nasa.gov/climate_resources/24/graphic-the-relentless-rise-of-carbon-dioxide/">several changes in our climate</a>. </p>
<p>This is because CO₂ represents a tiny part of Earth’s atmosphere. It is measured in parts per million (ppm) which means that for every carbon dioxide molecule there are a million others. Its concentration is just 0.041%, but even a small percentage change represents a big change in concentration. </p>
<p>We can tell what <a href="https://climate.nasa.gov/climate_resources/24/graphic-the-relentless-rise-of-carbon-dioxide/">Earth’s atmosphere and climate were like in the distant past</a> by analysing bubbles of ancient air trapped in ice. During Earth’s ice ages, the concentration of carbon dioxide was around 200ppm. During the warmer interglacial periods, it hovered around 280ppm, but since the 1950s, it <a href="http://scrippsco2.ucsd.edu/history_legacy/keeling_curve_lessons.html">has continued to rise relentlessly</a>. By 2013, CO₂ levels <a href="https://climate.nasa.gov/news/916/for-first-time-earths-single-day-co2-tops-400-ppm/">surpassed 400ppm for the first time in recorded history</a>. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/299988/original/file-20191103-88382-4i000a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/299988/original/file-20191103-88382-4i000a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=375&fit=crop&dpr=1 600w, https://images.theconversation.com/files/299988/original/file-20191103-88382-4i000a.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=375&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/299988/original/file-20191103-88382-4i000a.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=375&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/299988/original/file-20191103-88382-4i000a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=471&fit=crop&dpr=1 754w, https://images.theconversation.com/files/299988/original/file-20191103-88382-4i000a.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=471&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/299988/original/file-20191103-88382-4i000a.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=471&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">This graph, based on samples of air bubbles fro ice cores and direct measurements of carbon dioxide, shows the rise of atmospheric carbon dioxide since the industrial revolution.</span>
<span class="attribution"><span class="source">NASA</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>This rise represents almost a doubling in concentration, and it clear that, in the recipe for Earth’s surface temperature, carbon dioxide and other greenhouse gases are to be used in moderation. </p>
<h2>The role of water</h2>
<p>Like flour for a cake, water is an important ingredient of the Earth’s surface. Water makes temperature move slowly. That’s why the temperatures in tropical rainforests does not change much, but the Sahara desert is cold at night. Earth is rich in water.</p>
<p>Let’s have a look at our solid planets. Mercury is the closest planet to the Sun, but it has a very thin atmosphere and is not the warmest planet. Venus is very, very hot. Its atmosphere is rich in carbon dioxide (over 96%) and it is very dense.</p>
<p>The atmosphere of Mars is also rich in carbon dioxide (above 96%), but it is extremely thin (1% of Earth’s atmosphere), very dry and located further away from the Sun. This combination makes the planet an incredibly cold place.</p>
<p>The absence of water makes the temperature on Mars change a lot. The Mars exploration rovers (<a href="https://www.nature.com/articles/nature03640">Spirit at Gusev Crater</a> and <a href="https://science.sciencemag.org/content/324/5930/1058.editor-summary">Opportunity at Meridiani Planun</a>) experienced temperatures ranging from a few degrees Celsius above zero to minus 80°C at night: every single Martian day, known as sol. </p>
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<p>
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<strong>
Read more:
<a href="https://theconversation.com/curious-kids-what-are-some-of-the-challenges-to-mars-travel-105030">Curious Kids: What are some of the challenges to Mars travel?</a>
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<h2>Terraforming or terra fixing</h2>
<p>One of the interesting challenges we face while building space payloads, like we do at Griffith University, is to build instruments that can withstand such a wide temperature range.</p>
<p>I love conversations about terraforming. This is the idea that we could fly to a planet with an unbreathable atmosphere and fix it by using some sort of machine to filter nasty gases and release good ones we need to survive, at the correct amount. That is a recurrent theme in many science fiction films, including <a href="https://www.imdb.com/title/tt0090605/">Aliens</a>, <a href="https://www.imdb.com/title/tt0100802/">Total Recall</a> and <a href="https://www.imdb.com/title/tt0199753/">Red Planet</a>.</p>
<p>I hope we can fix our own atmosphere on Earth and reduce our planet’s fever.</p><img src="https://counter.theconversation.com/content/126337/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Paulo de Souza is a Professor and Head of the School of Information and Communication Technology at Griffith University and collaborating scientist of the NASA's Mars Exploration Rover Project. </span></em></p>The atmosphere of Mars is more than 96% carbon dioxide, but the planet is cold because its atmosphere is extremely thin, very dry and further away from the Sun.Paulo de Souza, Professor, Griffith UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1232382019-10-29T12:46:23Z2019-10-29T12:46:23ZClimate crisis – here’s what the experts recommend we do<figure><img src="https://images.theconversation.com/files/299176/original/file-20191029-183132-n14xqb.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C2400%2C1451&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://flickr.com/photos/volvob12b/10814060045/">Bernard Spragg/Flickr</a></span></figcaption></figure><p>The global strike on Friday September 20, 2019 was the largest demonstration for climate action in history. The movement that started with Swedish teenager Greta Thunberg in August 2018 has now <a href="https://theconversation.com/uk/topics/climate-strikes-66457">mobilised millions</a>, while <a href="https://theconversation.com/uk/topics/extinction-rebellion-69561">Extinction Rebellion</a> and other protest groups have <a href="https://www.theguardian.com/environment/2019/sep/23/extinction-rebellion-plans-new-london-shutdowns-over-climate-crisis">escalated</a> their campaigns on streets around the world. From the efforts of activists in different countries, radical “<a href="https://theconversation.com/uk/topics/green-new-deal-40625">Green New Deals</a>” are emerging as a bold, political response to the climate crisis.</p>
<p>“<a href="https://www.youtube.com/watch?v=TMrtLsQbaok&feature=youtu.be">The world is waking up</a>,” Thunberg told world leaders at the recent UN Climate Action Summit. “And change is coming whether you like it or not.”</p>
<p>But how long that awakening takes could be decisive for warming this century. A report published ahead of the summit declared that the <a href="https://public.wmo.int/en/media/press-release/global-climate-2015-2019-climate-change-accelerates">impacts of climate change are accelerating</a> – growth rates of carbon dioxide (CO₂) in the atmosphere were nearly 20% higher in the 2015-19 period than the previous five years, while the average rate of sea level rise has increased to 5mm per year over roughly the same period.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/294119/original/file-20190925-51434-1ibtooo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/294119/original/file-20190925-51434-1ibtooo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/294119/original/file-20190925-51434-1ibtooo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=434&fit=crop&dpr=1 600w, https://images.theconversation.com/files/294119/original/file-20190925-51434-1ibtooo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=434&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/294119/original/file-20190925-51434-1ibtooo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=434&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/294119/original/file-20190925-51434-1ibtooo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=546&fit=crop&dpr=1 754w, https://images.theconversation.com/files/294119/original/file-20190925-51434-1ibtooo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=546&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/294119/original/file-20190925-51434-1ibtooo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=546&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Predicted sea level rise this century if warming reaches 2.6°C, 4.5°C or 8.5°C by 2100.</span>
<span class="attribution"><a class="source" href="https://www.ipcc.ch/srocc/download-report/">IPCC</a>, <span class="license">Author provided</span></span>
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</figure>
<p><a href="https://www.bbc.co.uk/news/science-environment-49773869">One author warned</a> that limiting global temperature rise to 2°C would require tripling current commitments to reduce emissions. To hold temperatures at 1.5°C above pre-industrial levels, global ambition would need to increase by a factor of five.</p>
<p>The debate over whether climate change is happening is over, and the conversation about what should be done is beginning in earnest. As such, for the past few weeks, we’ve asked experts from around the world to describe how the world should respond to the threat of climate breakdown. We share their insights here.</p>
<h2>The state of the Earth</h2>
<p>Nowhere are the effects of climate change more visible than in the Arctic – a region that’s estimated to be warming at least <a href="https://theconversation.com/arctic-breakdown-what-climate-change-in-the-far-north-means-for-the-rest-of-us-123309">twice as fast as the global average</a>. Arctic sea ice reached its second-lowest extent on record in September 2019 – <a href="https://www.theguardian.com/environment/2018/feb/27/arctic-warming-scientists-alarmed-by-crazy-temperature-rises">a mere 1.6m square miles</a>.</p>
<p>A new report by the Intergovernmental Panel on Climate Change (IPCC) has revealed the changes that are underway in the oceans and the ice-covered regions of the world, and <a href="https://theconversation.com/another-grim-climate-report-on-oceans-what-will-it-take-to-address-the-compounding-problems-123894">the message is stark</a>. </p>
<p><strong>“Glaciers and ice sheets are shrinking. Global sea level is rising at more than twice the rate of the 20th century. The ocean is warming, becoming more acidic and losing oxygen. Fifty percent of coastal wetlands have been lost over the past 100 years. Species are shifting, biodiversity is declining and ecosystems are losing their integrity and function.”</strong></p>
<p><strong>– Cassandra Brooks, University of Colorado Boulder</strong></p>
<p>Earth’s oceans have absorbed more than <a href="https://theconversation.com/ipcc-report-paints-catastrophic-picture-of-melting-ice-and-rising-sea-levels-and-reality-may-be-even-worse-124193">90% of the excess heat</a> in the global climate system, but not without repercussions. <a href="https://theconversation.com/search/result?sg=e6dece65-1017-405a-821c-776ac71a39da&sp=1&sr=1&url=%2Fmarine-heatwaves-are-getting-hotter-lasting-longer-and-doing-more-damage-95637">Marine heatwaves</a> are <a href="https://theconversation.com/extreme-weather-caused-by-climate-change-has-damaged-45-of-australias-coastal-habitat-120671">causing coral reefs to bleach</a> and <a href="https://theconversation.com/suffering-in-the-heat-the-rise-in-marine-heatwaves-is-harming-ocean-species-112839">mass die-offs of fish and other wildlife</a>. Not only does this added ocean heat wreak havoc on marine ecosystems, but it <a href="https://theconversation.com/ocean-warming-is-changing-the-relationship-coastal-communities-have-with-the-ocean-122599">is changing the relationship between coastal communities and the ocean</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/294341/original/file-20190926-51401-143rmsg.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/294341/original/file-20190926-51401-143rmsg.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/294341/original/file-20190926-51401-143rmsg.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=199&fit=crop&dpr=1 600w, https://images.theconversation.com/files/294341/original/file-20190926-51401-143rmsg.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=199&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/294341/original/file-20190926-51401-143rmsg.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=199&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/294341/original/file-20190926-51401-143rmsg.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=250&fit=crop&dpr=1 754w, https://images.theconversation.com/files/294341/original/file-20190926-51401-143rmsg.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=250&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/294341/original/file-20190926-51401-143rmsg.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=250&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Everywhere is warming, but the Arctic is warming fastest.</span>
<span class="attribution"><a class="source" href="https://theconversation.com/time-will-tell-if-this-is-a-record-summer-for-greenland-ice-melt-but-the-pattern-over-the-past-20-years-is-clear-119307">The Conversation/HadCRUT v4</a></span>
</figcaption>
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<p>Wildlife populations are <a href="https://theconversation.com/animals-will-struggle-to-adapt-fast-enough-to-cope-with-climate-change-study-finds-120857">struggling to adapt</a> to the disruption, both in the oceans and on land. As a result, a landmark report from an international team of biodiversity experts earlier in 2019 called for “<a href="https://theconversation.com/revolutionary-change-needed-to-stop-unprecedented-global-extinction-crisis-116166">transformative change</a>” to economies and societies to prevent up to a million species going extinct. </p>
<h2>Five steps to restrain emissions right now</h2>
<p><strong>“The UK, Norway, Sweden and France have written a target of net-zero emissions into law, [but] targets are, by definition, a statement of nothing more than intent. In and of themselves, they do not remove a single molecule of carbon dioxide from the atmosphere.”</strong></p>
<p><strong>– Rebecca Willis, Lancaster University</strong></p>
<p>Limiting global temperature rise to 1.5°C means the world has to be at net-zero carbon emissions by 2050. But it’s cumulative emissions that count – if countries leave decarbonisation until the last minute, <a href="https://theconversation.com/conservatives-nuclear-fusion-by-2040-pledge-is-wishful-thinking-124404">it will be too late</a>. Rebecca Willis, a professor of climate and energy policy at Lancaster University in the UK, outlines <a href="https://theconversation.com/five-things-every-government-needs-to-do-right-now-to-tackle-the-climate-emergency-123344">five measures that can begin to restrain emissions</a> right now:</p>
<ol>
<li><p>Task all government departments with a climate agenda so that they’re obligated to show how their policies will contribute to emissions cuts.</p></li>
<li><p>Engage the public in developing climate strategies with citizens’ assemblies and involve workers in designing policy to ensure a “<a href="https://neweconomics.org/2018/11/working-together-for-a-just-transition">just transition</a>” from carbon-intensive industries like coal mining.</p></li>
<li><p>Enact “<a href="https://fabians.org.uk/promises-promises/">symbolic policies</a>” to set the investment climate and catalyse radical change – ban advertising for petrol cars for instance, or allow people to generate and sell renewable energy at home.</p></li>
<li><p><a href="https://theconversation.com/retire-all-existing-and-planned-fossil-fuel-power-plants-to-limit-warming-to-1-5-c-119607">Keep all remaining fossil fuels in the ground</a> – ban oil and gas exploration and end the <a href="https://www.theatlantic.com/science/archive/2019/05/how-much-does-world-subsidize-oil-coal-and-gas/589000/">US$5.2 trillion</a> spent on <a href="https://theconversation.com/fossil-fuel-subsidies-reach-us-87-billion-in-eu-countries-and-theyre-growing-123733">subsidising the fossil fuel industry</a> each year.</p></li>
<li><p>Set aside <a href="https://theconversation.com/cant-we-just-remove-carbon-dioxide-from-the-air-to-fix-climate-change-not-yet-45621">negative emission technologies</a> – carbon capture and storage might play a role in absorbing greenhouse gases from the atmosphere in future, but they don’t exist at a meaningful scale yet. Relying on them <a href="https://www.frontiersin.org/articles/10.3389/fclim.2019.00004/full">distracts resources from cutting emissions now</a>.</p></li>
</ol>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/292963/original/file-20190918-187985-xts1an.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/292963/original/file-20190918-187985-xts1an.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/292963/original/file-20190918-187985-xts1an.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/292963/original/file-20190918-187985-xts1an.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/292963/original/file-20190918-187985-xts1an.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/292963/original/file-20190918-187985-xts1an.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/292963/original/file-20190918-187985-xts1an.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Protesters demand an end to fossil fuel exploration.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/washington-november-29-marchers-take-part-345374051?src=4kxlTXCu_BZDmFjaFbk9-g-1-55">Rena Schild/Shutterstock</a></span>
</figcaption>
</figure>
<h2>Think about natural climate solutions</h2>
<p>There are technologies that already exist which are very good at capturing CO₂. Plants have perfected the process of turning carbon in the air into solid, living material over billions of years. <a href="https://theconversation.com/george-monbiot-q-a-how-rejuvenating-nature-could-help-fight-climate-change-115313">Natural climate solutions</a> mobilise this potential by <a href="https://theconversation.com/rewild-25-of-the-uk-for-less-climate-change-more-wildlife-and-a-life-lived-closer-to-nature-123836">restoring forests, wetlands and other habitats</a>. One estimate from the UK suggests each hectare of new forest can <a href="https://theconversation.com/rewilding-is-essential-to-the-uks-commitment-to-zero-carbon-emissions-107541">absorb the annual carbon emissions of 90 cars</a>. </p>
<p>But <a href="https://theconversation.com/climate-explained-how-different-crops-or-trees-help-strip-carbon-dioxide-from-the-air-123590">it’s not as simple as letting nature do all the hard work</a>, says Sebastian Leuzinger, an associate professor at the Auckland University of Technology. The “right tree should be planted at the right time in the right place”:</p>
<ul>
<li><p>Tree species that grow fast are able to store carbon more rapidly, but slower, bigger trees will ultimately store more in the long run.</p></li>
<li><p>Non-native trees may be better at absorbing carbon efficiently than native species, so keep an open mind to their role.</p></li>
<li><p>When choosing a species to plant, trust local foresters and the community that will have to live alongside and nurture them.</p></li>
</ul>
<p>Natural climate solutions can also help society adapt to the inevitable changes ahead. Zita Sebesvari, head of environmental vulnerability and ecosystem services at United Nations University, argues that <a href="https://theconversation.com/sea-level-rise-is-inevitable-but-what-we-do-today-can-still-prevent-catastrophe-for-coastal-regions-124129">the value of rewilding</a> here is two-fold: removing the CO₂ that exacerbates climate change while mitigating its impacts.</p>
<blockquote>
<p>Coastal wetlands, marshes and mangrove swamps can retain sediments and can grow vertically at rates equal to or greater than the mean rate of sea level rise. These habitats can also <a href="https://www.frontiersin.org/articles/10.3389/fmars.2017.00143/full">accumulate carbon 40 times quicker</a> per hectare than tropical forests.</p>
</blockquote>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/294131/original/file-20190925-51410-12s0e2f.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/294131/original/file-20190925-51410-12s0e2f.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/294131/original/file-20190925-51410-12s0e2f.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/294131/original/file-20190925-51410-12s0e2f.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/294131/original/file-20190925-51410-12s0e2f.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/294131/original/file-20190925-51410-12s0e2f.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/294131/original/file-20190925-51410-12s0e2f.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Replanting mangroves could protect tropical coastlines from flooding and storm surges, while absorbing atmospheric carbon and slowing climate change at the same time.</span>
<span class="attribution"><span class="source">Janine Kandel/UNU-EHS</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>How to feed the planet</h2>
<p>Leaving room for nature seems radical when humans currently exploit more than <a href="https://theconversation.com/ipccs-land-report-shows-the-problem-with-farming-based-around-oil-not-soil-121643">70% of the Earth’s ice-free surface</a>, much of it to grow food. It’s estimated that <a href="https://theconversation.com/un-climate-change-report-land-clearing-and-farming-contribute-a-third-of-the-worlds-greenhouse-gases-121551">a third of all greenhouse gas emissions</a> originate with agriculture – from deforesting farmland to raising livestock that belch methane.</p>
<p>Farming for meat and dairy can use up to 100 times the land area to <a href="https://ourworldindata.org/meat-production">produce a single gram of protein</a> compared to beans, nuts and other plant sources. Little wonder that people are encouraged to eat less of it, and Alessandro Demaio, a fellow in global health at the University of Copenhagen, recommends a “<a href="https://theconversation.com/how-to-feed-a-growing-population-healthy-food-without-ruining-the-planet-108994">planetary health diet</a>” which involves reducing meat intake in Western countries by 50%. He also calls for:</p>
<ul>
<li><p>Recycling organic waste as fertiliser and investing in <a href="https://theconversation.com/au/topics/agroforestry-28625">agroforestry</a> – where trees are grown around crops to increase biodiversity.</p></li>
<li><p>Breeding drought-resistant crop strains, making animal feed more nutritious and creating additives that can make livestock <a href="https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(18)33179-9/fulltext?utm_campaign=tleat19&utm_source=hub_page">emit 30% less methane</a>.</p></li>
<li><p>Reducing food waste and restoring land and ocean habitats. </p></li>
</ul>
<p>Sean Beer, a lecturer in agriculture at Bournemouth University, argues that <a href="https://theconversation.com/what-does-a-healthy-diet-look-like-for-me-and-the-planet-it-depends-where-you-live-123470">eating more local and seasonal produce</a> could go some way to decarbonising agriculture.</p>
<p><a href="https://theconversation.com/edible-forests-can-fight-land-clearing-and-world-hunger-at-the-same-time-122540">Reviving traditional food supply systems</a> may also be key to guaranteeing sustainable diets for all, says Jagannath Adhikari, a sessional lecturer at the University of New South Wales.</p>
<blockquote>
<p>More than 820m people suffer from hunger, and about two billion people face moderate food insecurity – meaning they do not always know when their next meal will come. After a decade of slow decline, climate change is driving this number up again, particularly in Africa and Asia, where competition over land for both farming and forest conservation is acute.</p>
</blockquote>
<p>In parts of the Himalayas, <a href="https://theconversation.com/edible-forests-can-fight-land-clearing-and-world-hunger-at-the-same-time-122540">the answer to this problem is “food forests”</a>. Local people plant useful trees and grow crops in the woodland near their homes, and protect what grows there naturally. They harvest what they need – mushrooms, honey, roots and edible plants – and sell any surplus at a market. Since community rights were restored to forest management here, worrying trends in <a href="https://www.intechopen.com/books/global-exposition-of-wildlife-management/community-forestry-management-and-its-role-in-biodiversity-conservation-in-nepal">deforestation</a> and <a href="https://www.researchgate.net/publication/332966490_Reductions_in_deforestation_and_poverty_from_decentralized_forest_management_in_Nepal">poverty</a> have been reversed.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/292930/original/file-20190918-149001-14p448p.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/292930/original/file-20190918-149001-14p448p.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/292930/original/file-20190918-149001-14p448p.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/292930/original/file-20190918-149001-14p448p.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/292930/original/file-20190918-149001-14p448p.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/292930/original/file-20190918-149001-14p448p.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/292930/original/file-20190918-149001-14p448p.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/292930/original/file-20190918-149001-14p448p.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A woman sells bamboo shoots in Pokhara, Nepal. These bamboo shoots are collected in forests at high altitude, 2,200-2,600 metres above sea level.</span>
<span class="attribution"><span class="source">Jagannath Adhikari</span></span>
</figcaption>
</figure>
<h2>Climate action means transforming the economy</h2>
<p>Some politicians are now supporting policies that <a href="https://theconversation.com/the-green-new-deal-is-going-global-115961">address climate change by transforming national economies</a> under the umbrella of a Green New Deal. Spain’s socialist party was recently reelected on a Green New Deal platform, for example, and, in the UK, the <a href="https://theconversation.com/labours-green-new-deal-is-among-the-most-radical-in-the-world-but-can-it-be-done-by-2030-123982">Labour Party has voted in favour of one</a>. </p>
<p>The idea was <a href="https://www.theguardian.com/environment/audio/2019/apr/23/how-the-green-new-deal-was-hatched-in-a-london-bar-podcast">born in the UK in 2007</a>, but has been gaining ground around the world lately, especially in the US where it has been championed by congresswoman Alexandria Ocasio-Cortez. Although the specifics vary, a Green New Deal involves large investments in clean energy sector jobs and infrastructure to decarbonise the economy and correct inequalities through job guarantees and universal basic services such as free public transport and healthcare. Governments would also be expected to <a href="https://theconversation.com/fossil-fuel-subsidies-reach-us-87-billion-in-eu-countries-and-theyre-growing-123733">slash or eliminate the billions they spend on subsidising the cost of fossil fuels</a>. </p>
<p>Experts also urge for the inclusion of the insurance industry in Green New Deal discussions. A <a href="https://www.cisl.cam.ac.uk/business-action/sustainable-finance/climatewise/news/investors-and-lenders-need-better-tools-to-manage-climate-risk-to-homes-mortgages-and-assets-finds-new-research">recent report from Cambridge University</a> emphasised the large losses insurers will face under climate change and warns that <a href="https://theconversation.com/echoes-of-2008-could-climate-change-spark-a-global-financial-crisis-112497">it could spark a global financial crisis</a>. </p>
<p><strong>>“If governments respond appropriately to the urgent warning issued by the Intergovernmental Panel on Climate Change (IPCC) in October [2018], efforts to phase out fossil fuels will have to ramp up considerably — and quickly.”</strong></p>
<p><strong>– Kyla Tienhaara, Queen’s University, Canada</strong></p>
<p>Already, <a href="https://theconversation.com/directors-are-in-the-crosshairs-of-corporate-climate-litigation-117737">there has been a slew of lawsuits against the largest fossil fuel companies</a> in an effort to hold them accountable for misleading the public on the risks of climate change while selling products that have contributed to it. Litigation, thus far, has not been successful, but the tide may be turning.</p>
<p>In the US, more than a dozen cities, counties and states are seeking damages from energy companies for the the costs of climate change, from retrofitting storm drains to upgrading sea walls. These lawsuits draw on <a href="https://theconversation.com/court-tobacco-decision-may-set-precedent-for-cases-against-fossil-fuel-companies-123436">litigation against tobacco companies</a> and on scientific research that attributes greenhouse gas emissions to energy companies.</p>
<p>In the past, “the plaintiffs had difficulties tracing climate harms to specific emissions made by particular corporations … Scientific research has evolved dramatically since then.” says Lisa Benjamin, from Lewis & Clark College of Law, in Portland, Oregon.</p>
<p>For example, in Europe, a German court has agreed to hear <a href="https://theconversation.com/directors-are-in-the-crosshairs-of-corporate-climate-litigation-117737">a Peruvian farmer’s case against the German energy giant RWE</a> for its role in melting the glaciers near his hometown of Huaraz and raising the risks of landslides and flooding. A study found RWE was responsible for 0.47% of historic emissions, so the farmer is seeking 0.47% of the cost for his community to adapt to climate change. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/296984/original/file-20191014-135521-1gxdsge.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/296984/original/file-20191014-135521-1gxdsge.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/296984/original/file-20191014-135521-1gxdsge.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/296984/original/file-20191014-135521-1gxdsge.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/296984/original/file-20191014-135521-1gxdsge.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/296984/original/file-20191014-135521-1gxdsge.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/296984/original/file-20191014-135521-1gxdsge.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">
<figcaption>
<span class="caption">Melting glaciers threaten the village of Huaraz, Peru.</span>
<span class="attribution"><a class="source" href="https://upload.wikimedia.org/wikipedia/commons/2/2f/Huascaran_Huandoy_Chopicalqui_seen_from_Huaraz.JPG">Uwebart/Wikimedia</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>As the impacts of climate change become more clear, Thunberg’s not the only one questioning the “<a href="https://theconversation.com/greta-thunbergs-radical-climate-change-fairy-tale-is-exactly-the-story-we-need-124252">fairy tales of eternal economic growth</a>”. Producing stuff consumes energy, and producing more stuff, whether it’s fast fashion or smartphones, means the ongoing and growing consumption of energy. </p>
<p>“This makes it very hard to decarbonise the economy,” says Simon Mair at the University of Surrey. If we stopped chasing productivity growth, decarbonisation would come easier, we’d have less “crap” and we might <a href="https://theconversation.com/how-getting-rid-of-shit-jobs-and-the-metric-of-productivity-can-combat-climate-change-123541">start investing time and human energy into good jobs that matter</a>, like teaching and nursing. </p>
<h2>The media is finally listening to the experts</h2>
<p>Despite the potentially massive implications of a 2°C rise in global temperature, climate change has <a href="https://theconversation.com/why-is-climate-change-still-not-top-of-the-news-agenda-123800">remained low on the news agenda</a>. Journalists and their news organisations have largely failed to give climate change the attention it deserves and have failed to press political figures on climate issues and policies. </p>
<p>Years ago, climate journalists threw away the notion of putting scientific fact and climate denier opinion on equal ground. Other media are finally catching up and providing analysis and verification, and improving the scientific literacy of their audience. They are connecting climate change to local stories, <a href="https://theconversation.com/the-counter-intuitive-solution-to-getting-people-to-care-about-climate-change-120136">focusing on solutions</a> (instead of “doom and gloom” coverage) and <a href="https://theconversation.com/language-matters-when-the-earth-is-in-the-midst-of-a-climate-crisis-117796">adjusting their language to describe the “climate crisis”</a>.</p>
<p>These shifts in journalism may yield more action on climate change. Young people tend to avoid negative news headlines; they don’t want their climate coverage to present a bleak and certain future. Instead, they want <a href="https://theconversation.com/how-the-media-can-help-young-people-create-zero-carbon-societies-123558">stories about the “system change” necessary to create zero-carbon societies</a>, says Julie Doyle, from the University of Brighton. It’s not that they can’t handle the bad news, but that “they wanted to be involved in rethinking socioeconomic systems, and are inspired and empowered by working together.”</p>
<p>That’s why “<a href="https://theconversation.com/climate-strikes-greta-thunberg-calls-for-system-change-not-climate-change-heres-what-that-could-look-like-112891">system change not climate change</a>” has became the rallying cry of the young climate strikers. Thunberg’s journey from a lonely vigil outside the Swedish parliament to a Nobel Peace Prize nominee at the head of a global movement took just over a year. It seems the world really is waking up, but now comes the hard part – changing the systems that fuel the climate crisis before it’s too late.</p>
<p><em>This article was amended on November 12 2019 to clarify an error. The earlier story said global emissions of carbon dioxide grew by 20% between 2015 and 2019. Instead, growth rates of carbon dioxide were nearly 20% higher in the 2015-19 period than the previous five years.</em></p>
<hr>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=140&fit=crop&dpr=1 600w, https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=140&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=140&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=176&fit=crop&dpr=1 754w, https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=176&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/263883/original/file-20190314-28475-1mzxjur.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=176&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p><em><a href="https://theconversation.com/imagine-newsletter-researchers-think-of-a-world-with-climate-action-113443?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=Imagineheader1123238">Click here to subscribe to our climate action newsletter. Climate change is inevitable. Our response to it isn’t.</a></em></p><img src="https://counter.theconversation.com/content/123238/count.gif" alt="The Conversation" width="1" height="1" />
In this special global newsletter, experts share their visions for ambitious climate action.Hannah Hoag, On Leave, The Conversation CanadaJack Marley, Environment + Energy Editor, UK editionLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1254902019-10-22T18:57:40Z2019-10-22T18:57:40ZClimate explained: how volcanoes influence climate and how their emissions compare to what we produce<figure><img src="https://images.theconversation.com/files/297844/original/file-20191021-56220-1352qq3.jpg?ixlib=rb-1.1.0&rect=31%2C100%2C5114%2C3344&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Rapid and voluminous volcanic eruptions around 252 million years ago can be linked with a mass extinction event.</span> <span class="attribution"><span class="source">from www.shutterstock.com</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><figure class="align-left ">
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<p><em><strong><a href="https://theconversation.com/nz/topics/climate-explained-74664">Climate Explained</a></strong> is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.</em> </p>
<p><em>If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz</em></p>
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<p><strong>Everyone is going on about reducing our carbon footprint, zero emissions, planting sustainable crops for biodiesel etc. Is it true what the internet posts say that a volcano eruption for a few weeks will make all our efforts null and void?</strong></p>
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<p>The pretext to this question is understandable. The forces of nature are so powerful and operate at such a magnitude that human efforts to influence our planet may seem pointless. </p>
<p>If one volcanic eruption could alter our climate to such a degree that our world rapidly becomes an “icehouse” or a “hothouse”, then perhaps our efforts to mitigate anthropogenic climate change are a waste of time? </p>
<p>To answer this question we need to examine how our atmosphere formed and what geological evidence there is for volcanically induced climate change. We also need to look at recent data comparing volcanic and human greenhouse gas emissions. </p>
<p>There is evidence for catastrophic climate change from very large, protracted volcanic eruptions in the geological record. But in more recent times we have learned that volcanic emissions can lead to shorter-term cooling and longer-term warming. And the killer-punch evidence is that human-induced greenhouse gas emissions far exceed those of volcanic activity, particularly since 1950.</p>
<h2>Forging Earth’s atmosphere</h2>
<p>Let’s go back to first principles and look at <a href="https://www.scientificamerican.com/article/evolution-of-earth/">where our atmosphere came from</a>. Earth is 4.56 billion years old. The common consensus is that Earth’s atmosphere results from three main processes: </p>
<p><strong>1.</strong> remnants of primordial solar nebula gases from the time of earliest planet formation</p>
<p><strong>2.</strong> outgassing of the Earth’s interior from volcanic and related events</p>
<p><strong>3.</strong> the production of oxygen from photosynthesis. </p>
<p>There have also been contributions over time from comets and asteroid collisions. Of these processes, internal planetary degassing is the most important atmosphere-generating process, particularly during the first of four aeons of Earth’s history, the <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/hadean">hot Hadean</a>. </p>
<p>Volcanic eruptions have contributed to this process ever since and provided the bulk of our atmosphere and, therefore, the climate within our atmosphere.</p>
<p>Next is the question of volcanic eruptions and their influence on climate. Earth’s climate has changed over geological time. There have been periods of an <a href="https://theconversation.com/hothouse-earth-our-planet-has-been-here-before-heres-what-it-looked-like-101413">ice-free “hothouse Earth”</a>. Some argue that sea levels were <a href="https://en.wikipedia.org/wiki/Past_sea_level">200 to 400 metres higher than today</a> and a significant proportion of Earth’s continents were submerged beneath sea level. </p>
<p>At other times, during a “<a href="http://www.bbc.com/earth/story/20150112-did-snowball-earth-make-animals">snowball Earth</a>”, our planet was covered in ice even at the equator. </p>
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Read more:
<a href="https://theconversation.com/climate-explained-why-we-wont-be-heading-into-an-ice-age-any-time-soon-123675">Climate explained: why we won't be heading into an ice age any time soon</a>
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<p>What contribution have volcanic eruptions made to this variation in climate? As an example of a major influence, some scientists link mass extinctions to major volcanic eruption events. </p>
<p>The most famous such association is that of the eruption of volcanoes that produced the <a href="https://link.springer.com/article/10.1007/s11434-008-0543-7">Siberian Traps</a>. This is a large region of thick volcanic rock sequences, some 2.5 to 4 million square kilometres, in an area in Russia’s eastern provinces. Rapid and voluminous volcanic eruptions around 252 million years ago released sufficient quantities of sulphate aerosols and carbon dioxide to trigger short-duration volcanic winters, and long-duration climate warming, over a period of 10s of thousands of years. </p>
<p>The Siberian Trap eruptions were a <a href="https://phys.org/news/2018-09-end-permian-extinction-earth-species-instantaneous.html">causal factor in Earth’s largest mass extinction event</a> (at the end of the Permian period), when 96% of Earth’s marine species and 70% of terrestrial life ceased to exist.</p>
<h2>Natural climate change over past 100 million years</h2>
<p>Geological evidence indicates that natural processes can indeed radically change Earth’s climate. Most recently (in geological terms), over the past 100 million years ocean bottom waters have cooled, sea levels fallen and ice has advanced. Within this period there have also been spells of a hotter Earth, most likely caused by (natural) rapid releases in greenhouse gases. </p>
<p><em>Homo sapiens</em> has evolved during the past few million years largely during an ice age when up to two-kilometre-thick ice sheets covered large areas of the northern continents and sea levels were over 100 metres lower than today. This period ended 10,000 years ago when our modern interglacial warmer period began. </p>
<p>Astronomical cycles that lead to climate variations are well understood – for example, the Milankovitch cycles, which explain variations in Earth’s orbit around the sun, and the periodic nodding/swaying of our Earth’s axis. All of the geological and tectonic causes for this general longer-term Earth cooling are less well understood. Hypotheses include contributions from volcanoes and processes linked to the rise of the Himalayas and Tibet (from 55 million years ago).</p>
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Read more:
<a href="https://theconversation.com/climate-explained-why-we-need-to-cut-emissions-as-well-as-prepare-for-impacts-122030">Climate explained: why we need to cut emissions as well as prepare for impacts</a>
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<h2>Specific volcanic eruptions and climate impacts</h2>
<p>Researchers have studied specific <a href="https://earthdata.nasa.gov/learn/sensing-our-planet/volcanoes-and-climate-change">volcanic eruptions and climate change</a>. <a href="https://earthobservatory.nasa.gov/features/Volcano">Mount Pinatubo</a> (Philippines) produced one of the larger eruptions of recent times in 1991, releasing 20 million tonnes of sulphur dioxide and ash particles into the stratosphere. </p>
<p>These larger eruptions reduce solar radiation reaching the Earth’s surface, lower temperatures in the lower troposphere, and change atmospheric circulation patterns. In the case of Pinatubo, global tropospheric temperatures fell by up to 4°C, but northern hemisphere winters warmed. </p>
<p>Volcanoes erupt a mix of gases, including greenhouse gases, aerosols and gases that can react with other atmospheric constituents. Atmospheric reactions with volcanic gases can rapidly produce substances such as sulphuric acid (and related sulphates) that act as aerosols, cooling the atmosphere. </p>
<p>Longer-term additions of carbon dioxide have warming impacts. Larger-scale volcanic eruptions, whose ash clouds reach stratospheric levels, have the biggest climatic impacts: the larger and more prolonged the eruption period, the larger the impacts. </p>
<p>These types of eruptions are thought to have been a <a href="https://skepticalscience.com/volcanic-influence-on-lia.html">partial cause for the Little Ice Age period</a>, a global cooling event of about 0.5°C that lasted from the 15th to the late 19th century. Super volcanoes such as Yellowstone (USA), Toba (Indonesia) and Taupo (New Zealand) can, theoretically, produce very large-volume eruptions that have significant climate impacts, but there is uncertainty over how long these eruptions influence climate. </p>
<p>Perhaps the strongest evidence for answering whether our (human) emissions or volcanoes have a stronger influence on climate lies in the scale of greenhouse gas production. Since 2015, global anthropogenic carbon dioxide emissions have been around 35 to 37 billion tonnes per year. Annual volcanic CO₂ emissions are around 200 million tonnes. </p>
<p>In 2018, anthropogenic CO₂ emissions were 185 times higher than volcanic emissions. This is an astounding statistic and one of the factors persuading some geologists and natural scientists to propose a new geological epoch called the Anthropocene in recognition that humans are exceeding the impacts of many natural global processes, particularly since the 1950s.</p>
<p>There is evidence that volcanoes have strongly influenced climate on geological time scales, but, since 1950 in particular, it is <em>Homo sapiens</em> who has had by far the largest impact on climate. Let us not give up our CO₂ emission-reduction aspirations. Volcanoes may not save the day.</p><img src="https://counter.theconversation.com/content/125490/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Michael Petterson does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>There is evidence for catastrophic climate change from protracted volcanic eruptions in the past, but since the 1950s the emissions we produce far exceed those from volcanic activity.Michael Petterson, Professor of Geology, Auckland University of TechnologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1238862019-10-22T10:21:03Z2019-10-22T10:21:03ZThese celebrities cause 10,000 times more carbon emissions from flying than the average person<figure><img src="https://images.theconversation.com/files/294523/original/file-20190927-185379-8ibymn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/single-aircraft-flying-among-clouds-blue-781176490">Mental_Visual/Shutterstock.com</a></span></figcaption></figure><p>The jet-setting habits of Bill Gates and Paris Hilton mean that they produce an astonishing 10,000 times more carbon emissions from flying than the average person. This was the conclusion of <a href="https://authors.elsevier.com/a/1ZwGl_3fvx2jaK">my research</a> mining their social media accounts (tweets, Instagram and Facebook posts) as well as those of a number of other celebrities for clues as to where they were in the world over the course of 2017 and how they got there. As such, this estimate is conservative – they may well have taken more flights and not volunteered the information to their millions of followers.</p>
<p>This highlights the insane disparity in carbon emissions between the rich and the poor. In 2018, an average human emitted less than <a href="https://www.iea.org/geco/emissions/">five tonnes</a> of CO₂ overall. But this hides vast differences in individual contributions. In the case of air travel – the most energy-intensive human activity, no other human activity consumes as much energy in such a short time – the global average is 115kg CO₂ per person per year. Yet the vast majority of humanity never fly. This average is created by the staggering emissions of the richest proportion of humanity. I calculated that Bill Gates, for example, causes at least 1,600 tonnes of CO₂ to be emitted into the atmosphere – and this is from flying alone.</p>
<p>Of course, it’s not only celebrities who are the problem. Recently published <a href="https://www.theguardian.com/environment/2019/sep/25/1-of-english-residents-take-one-fifth-of-overseas-flights-survey-shows">figures</a> reveal that 1% of English residents are responsible for nearly one-fifth of all flights abroad. Nearly half (48%) of the population, meanwhile, did not take a single overseas flight in 2018.</p>
<h2>Carbon inequality</h2>
<p>Calling out the extent of this disparity is key given that humanity has agreed to stabilise global warming at 2°C. To achieve this goal, emissions of greenhouse gases have to be reduced drastically. The Paris Agreement accepts that the burden should be better shared around: countries that emit a lot per citizen should make greater contributions to decarbonisation.</p>
<p>Of course, there will also be disparity within each country: some high emitters as well as some who hardly contribute to global warming at all. I wanted to find out just how central the highest emitters might be to this question – just how much of the burden we should expect them to take on. Celebrities, by definition, are influential and often wealthy. While anecdotal evidence suggests that they are also frequent fliers, it has been difficult to determine their contributions to global warming. Very wealthy people are rarely represented in household surveys. To find out, I tracked the jet-set lifestyles of <a href="https://authors.elsevier.com/a/1ZwGl_3fvx2jaK">ten celebrities</a> by analysing their ample social media presence.</p>
<p><div data-react-class="InstagramEmbed" data-react-props="{"url":"https://www.instagram.com/p/Bx_xf88B3Bf/?utm_source=ig_web_copy_link","accessToken":"127105130696839|b4b75090c9688d81dfd245afe6052f20"}"></div></p>
<p>I analysed Twitter, Facebook and Instagram accounts for travel information volunteered. To narrow down the research, only air travel was recorded, though of course celebrities also cover (additional) distances by car. Social media posts were evaluated for journey start and end points, the type of aircraft used and the distances travelled. This information was used to calculate likely fuel use and associated emissions.</p>
<p>The vast emissions caused by these individuals suggest that a very small share of humanity has a very significant role in global warming. This likely equally true for a much wider range of economic, cultural and political elites. </p>
<h2>Flight shame</h2>
<p>We have known for a while that the world’s richest 10% produce <a href="https://www.theguardian.com/environment/2015/dec/02/worlds-richest-10-produce-half-of-global-carbon-emissions-says-oxfam">half of global carbon emissions</a>. But climate policies have so far tended to omit this issue of carbon inequality. </p>
<p>Worldwide, nations have focused on the decarbonisation of production within states, ignoring wild differences in consumption habits. And it’s increasingly looking like the climate crisis can’t be addressed while a small but growing group of super-emitters continue to increase their energy consumption and portray such lifestyles as desirable through their social media channels. Due to their wealth, these elites also <a href="https://www.forbes.com/profile/bill-gates/#6a72810d689f">exist outside</a> the market-based frameworks implemented to reduce emissions, such as carbon taxes, air passenger duties or carbon allowances for companies.</p>
<p>This is also the main issue highlighted by the growing youth movement demanding personal carbon accountability. As Greta Thunberg affirmed early on, “the bigger your carbon footprint, the bigger your moral duty”. And flying, as a very energy-intensive activity, has been identified as <a href="https://www.theguardian.com/environment/2019/apr/26/greta-thunberg-train-journey-through-europe-flygskam-no-fly">particularly harmful</a> and socially undesirable. </p>
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<img alt="" src="https://images.theconversation.com/files/294524/original/file-20190927-185383-w843pb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/294524/original/file-20190927-185383-w843pb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/294524/original/file-20190927-185383-w843pb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/294524/original/file-20190927-185383-w843pb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/294524/original/file-20190927-185383-w843pb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=565&fit=crop&dpr=1 754w, https://images.theconversation.com/files/294524/original/file-20190927-185383-w843pb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=565&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/294524/original/file-20190927-185383-w843pb.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">
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<span class="caption">For the moment, aeroplanes are only ever green when they’re grounded.</span>
<span class="attribution"><span class="source">Dan Meyers/Unsplash</span>, <a class="license" href="http://artlibre.org/licence/lal/en">FAL</a></span>
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<p>This has resulted in a major clash about the social and moral norms surrounding air travel. For decades, frequent fliers have been seen as living desirable lifestyles. To be a global traveller automatically infers a high social standing. Celebrities in particular have fostered this perspective through their communication of glamorous, globetrotting lifestyles. The ten celebrities studied in this research, for example, collectively reach out to 170m followers on Instagram alone.</p>
<p>But more and more people are beginning to question what is desirable, justifiable and indeed “normal” to consume. In the case of flying, this has come to be known as “flight shame”. In some circles, air travel is beginning to be framed as a destructive human activity. This is a major shift from the dominating production-oriented approach to climate change mitigation. The new focus on consumption challenges every individual to live within a sustainable personal carbon budget – and argues that this can be the most powerful way of forcing policy and industry change.</p>
<p>The implications of the flying habits of global superemitters are therefore far reaching. It is clear that governments need to follow the public and pay more attention to consumption in order to stem the growing class of very affluent people who contribute very significantly to emissions and encourage everyone else to aspire to such damaging lifestyles.</p>
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<p><em><a href="https://theconversation.com/imagine-newsletter-researchers-think-of-a-world-with-climate-action-113443?utm_source=TCUK&utm_medium=linkback&utm_campaign=TCUKengagement&utm_content=Imagineheader1123886">Click here to subscribe to our climate action newsletter. Climate change is inevitable. Our response to it isn’t.</a></em></p><img src="https://counter.theconversation.com/content/123886/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Stefan Gössling does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The vast emissions caused by these individuals suggest that a very small share of humanity has a very significant role in global warming.Stefan Gössling, Professor in Service Management and Service Studies, Lund UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1247622019-10-15T22:20:31Z2019-10-15T22:20:31ZClimate explained: the environmental footprint of electric versus fossil cars<figure><img src="https://images.theconversation.com/files/296991/original/file-20191015-98670-1xpjg8i.jpg?ixlib=rb-1.1.0&rect=107%2C98%2C5384%2C3565&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The best way to compare emissions from electric cars is to assess all phases of a life cycle analysis.</span> <span class="attribution"><span class="source">from www.shutterstock.com</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><figure class="align-left ">
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<p><em><strong><a href="https://theconversation.com/nz/topics/climate-explained-74664">Climate Explained</a></strong> is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.</em> </p>
<p><em>If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz</em></p>
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<p><strong>There is a lot of discussion on the benefits of electric cars versus fossil fuel cars in the context of lithium mining. Please can you tell me which one weighs in better on the environmental impact in terms of global warming and why?</strong></p>
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<p>Electric vehicles (EVs) seem very attractive at first sight. But when we look more closely, it becomes clear that they have a substantial carbon footprint and some downsides in terms of the extraction of lithium, cobalt and other metals. And they don’t relieve congestion in crowded cities. </p>
<p>In this response to the question, we touch briefly on the lithium issue, but focus mainly on the carbon footprint of electric cars.</p>
<p>The increasing use of lithium-ion batteries as a major power source in electronic devices, including mobile phones, laptops and electric cars has contributed to a <a href="https://www.sciencedirect.com/science/article/pii/S0301420717305457">58% increase in lithium mining</a> in the past decade worldwide. There seems little near-term risk of lithium being mined out, but there is an environmental downside. </p>
<p>The mining process requires extensive amounts of water, which can cause <a href="https://www.sciencedirect.com/science/article/pii/S0303243419300996">aquifer depletion and adversely affect ecosystems</a> in the Atacama Salt Flat, in Chile, the world’s largest lithium extraction site. But researchers have developed methods to <a href="https://www.sciencedirect.com/science/article/pii/S1385894719314780">recover lithium from water</a>. </p>
<p>Turning to climate change, it matters whether electric cars emit less carbon than conventional vehicles, and how much less.</p>
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Read more:
<a href="https://theconversation.com/climate-explained-why-dont-we-have-electric-aircraft-123910">Climate explained: why don't we have electric aircraft?</a>
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<h2>Emissions reduction potential of EVs</h2>
<p>The best comparison is based on a life cycle analysis which tries to consider all the emissions of carbon dioxide during vehicle manufacturing, use and recycling. Life cycle estimates are never entirely comprehensive, and emission estimates vary by country, as circumstances differ. </p>
<p>In New Zealand, <a href="https://www.mbie.govt.nz/assets/d7c93162b8/energy-in-nz-18.pdf">82% of energy for electricity generation came from renewable sources</a> in 2017. With these high renewable electricity levels for electric car recharging, compared with say Australia or China, <a href="https://www.eeca.govt.nz/news-and-events/media-releases/research-confirms-environmental-benefits-of-electric-vehicles/">EVs are better suited to New Zealand</a>. But this is only one part of the story. One should not assume that, overall, electric cars in New Zealand have a close-to-zero carbon footprint or are wholly sustainable. </p>
<p>A life cycle analysis of emissions considers three phases: the manufacturing phase (also known as cradle-to-gate), the use phase (well-to-wheel) and the recycling phase (grave-to-cradle). </p>
<h2>The manufacturing phase</h2>
<p>In this phase, the main processes are ore mining, material transformation, manufacturing of vehicle components and vehicle assembly. A <a href="https://www.sciencedirect.com/science/article/abs/pii/S0360544219307133">recent study</a> of car emissions in China estimates emissions for cars with internal combustion engines in this phase to be about 10.5 tonnes of carbon dioxide (tCO₂) per car, compared to emissions for an electric car of about 13 tonnes (including the electric car battery manufacturing). </p>
<p>Emissions from the manufacturing of a lithium-nickel-manganese-cobalt-oxide battery alone were estimated to be 3.2 tonnes. If the vehicle life is assumed to be 150,000 kilometres, emissions from the manufacturing phase of an electric car are higher than for fossil-fuelled cars. But for complete life cycle emissions, the study shows that EV emissions are 18% lower than fossil-fuelled cars.</p>
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Read more:
<a href="https://theconversation.com/how-electric-cars-can-help-save-the-grid-73914">How electric cars can help save the grid</a>
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<h2>The use phase</h2>
<p>In the use phase, emissions from an electric car are solely due to its upstream emissions, which depend on how much of the electricity comes from fossil or renewable sources. The emissions from a fossil-fuelled car are due to both upstream emissions and tailpipe emissions. </p>
<p>Upstream emissions of EVs essentially depend on the share of zero or low-carbon sources in the country’s electricity generation mix. To understand how the emissions of electric cars vary with a country’s renewable electricity share, consider Australia and New Zealand. </p>
<p>In 2018, <a href="https://www.tai.org.au/content/rooftops-providing-more-shelter-record-solar-contribution">Australia’s share of renewables in electricity generation was about 21%</a> (similar to Greece’s at 22%). In contrast, the share of renewables in New Zealand’s electricity generation mix was about 84% (less than France’s at 90%). Using these data and <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6358150/">estimates from a 2018 assessment</a>, electric car upstream emissions (for a battery electric vehicle) in Australia can be estimated to be about 170g of CO₂ per km while upstream emissions in New Zealand are estimated at about 25g of CO₂ per km on average. This shows that using an electric car in New Zealand is likely to be about seven times better in terms of upstream carbon emissions than in Australia. </p>
<p>The above studies show that emissions during the use phase from a fossil-fuelled compact sedan car were about 251g of CO₂ per km. Therefore, the use phase emissions from such a car were about 81g of CO₂ per km higher than those from a grid-recharged EV in Australia, and much worse than the emissions from an electric car in New Zealand.</p>
<h2>The recycling phase</h2>
<p>The key processes in the recycling phase are vehicle dismantling, vehicle recycling, battery recycling and material recovery. The estimated emissions in this phase, <a href="https://www.sciencedirect.com/science/article/abs/pii/S0360544219307133">based on a study in China</a>, are about 1.8 tonnes for a fossil-fuelled car and 2.4 tonnes for an electric car (including battery recycling). This difference is mostly due to the emissions from battery recycling which is 0.7 tonnes.</p>
<p>This illustrates that electric cars are responsible for more emissions than their petrol counterparts in the recycling phase. But it’s important to note the recycled vehicle components can be used in the manufacturing of future vehicles, and batteries recycled through direct cathode recycling can be used in subsequent batteries. This could have significant emissions reduction benefits in the future. </p>
<p>So on the basis of recent studies, fossil-fuelled cars generally emit more than electric cars in all phases of a life cycle. The total life cycle emissions from a fossil-fuelled car and an electric car in Australia were 333g of CO₂ per km and 273g of CO₂ per km, respectively. That is, using average grid electricity, EVs come out about 18% better in terms of their carbon footprint. </p>
<p>Likewise, electric cars in New Zealand work out a lot better than fossil-fuelled cars in terms of emissions, with life-cycle emissions at about 333 g of CO₂ per km for fossil-fuelled cars and 128g of CO₂ per km for electric cars. In New Zealand, EVs perform about 62% better than fossil cars in carbon footprint terms.</p><img src="https://counter.theconversation.com/content/124762/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>In New Zealand, where more than 80% of electricity is renewable, the carbon footprint of electric cars is 62% lower than that of fossil cars. But their lithium battery has other environmental impacts.Md Arif Hasan, PhD, PhD candidate, Te Herenga Waka — Victoria University of WellingtonRalph Brougham Chapman, Associate Professor , Director Environmental Studies, Te Herenga Waka — Victoria University of WellingtonLicensed as Creative Commons – attribution, no derivatives.