Direct CO2 Capture Machines Could Use ‘a Quarter of Global Energy’ in 2100
22 July 2019
Insights + Opinion
Climeworks Direct Air Capture plant, Switzerland. Credit: © Climeworks / Julia Dunlop
By Simon Evans
Machines that suck CO2 directly from the air could cut the cost of meeting global climate goals, a new study finds, but they would need as much as a quarter of global energy supplies in 2100.
<p>The research, published Monday in <a href="https://www.nature.com/articles/s41467-019-10842-5" target="_blank">Nature Communications</a>, is the first to explore the use of direct air capture (DAC) in multiple computer models. It shows that a "massive" and energy-intensive rollout of the technology could cut the cost of limiting warming to 1.5 or 2 C above <a href="https://www.carbonbrief.org/challenge-defining-pre-industrial-era" target="_blank">pre-industrial levels</a>.</p><p>But the study also highlights the "clear risks" of assuming that DAC will be available at scale, with global temperature goals being breached by up to 0.8 C if the technology then fails to deliver.</p><p>This means policymakers should not see DAC as a "panacea" that can replace immediate efforts to cut emissions, one of the study authors tells Carbon Brief, adding: "The risks of that are too high."</p><p>DAC should be seen as a "backstop for challenging abatement" where cutting emissions is too complex or too costly, says the chief executive of a startup developing the technology. He tells Carbon Brief that his firm nevertheless will "continuously push back on the 'magic bullet' headlines."</p>
<h4>Negative Emissions</h4><p>The 2015 <a href="https://www.ecowatch.com/tag/paris-agreement" rel="noopener noreferrer">Paris agreement</a> set a goal of limiting human-caused warming to "well below" 2 C and an ambition of staying below 1.5 C. Meeting this ambition <a href="https://www.carbonbrief.org/in-depth-qa-ipccs-special-report-on-climate-change-at-one-point-five-c" target="_blank">will require</a> the use of "<a href="https://www.carbonbrief.org/explainer-10-ways-negative-emissions-could-slow-climate-change" target="_blank">negative emissions technologies</a>" to remove excess CO2 from the atmosphere, according to the <a href="https://www.ipcc.ch/about/" target="_blank">Intergovernmental Panel on Climate Change</a> (IPCC).</p><p>This catch-all term covers a wide range of approaches, including planting trees, restoring peatlands and other "<a href="https://www.carbonbrief.org/analysis-how-natural-climate-solutions-can-reduce-the-need-for-beccs" target="_blank">natural climate solutions</a>." However, <a href="https://www.carbonbrief.org/explainer-how-shared-socioeconomic-pathways-explore-future-climate-change" target="_blank">model pathways</a> developed by researchers rely most heavily on bioenergy with carbon capture and storage (<a href="https://www.carbonbrief.org/beccs-the-story-of-climate-changes-saviour-technology" target="_blank">BECCS</a>). This is where biomass, such as wood pellets, is burned to generate electricity and the resulting CO2 is captured and stored.</p><p>The significant potential role for BECCS raises a number of concerns, with land areas <a href="https://linkinghub.elsevier.com/retrieve/pii/S0959378016303399" target="_blank">up to five times</a> the size of India devoted to growing the biomass needed in some model pathways.</p><p>One alternative is direct air capture, where machines are used to suck CO2 out of the atmosphere. If the CO2 is then buried underground, the process is sometimes referred to as direct air carbon capture and storage (DACCS).</p><p>The new study explores how DAC could help meet global climate goals with "lower costs," using two different <a href="https://www.carbonbrief.org/qa-how-integrated-assessment-models-are-used-to-study-climate-change" target="_blank">integrated assessment models</a> (IAMs). Study author <a href="https://www.imperial.ac.uk/people/a.gambhir" target="_blank">Dr. Ajay Gambhir</a>, senior research fellow at the <a href="https://www.imperial.ac.uk/grantham/" target="_blank">Grantham Institute for Climate Change</a> at Imperial College London, explains to Carbon Brief:</p><blockquote>"This is the first inter-model comparison … [and] has the most detailed representation of DAC so far used in IAMs. It includes two DAC technologies, with different energy inputs and cost assumptions, and a range of energy inputs including waste heat. The study uses an extensive sensitivity analysis [to test the impact of varying our assumptions]. It also includes initial analysis of the broader impacts of DAC technology development, in terms of material, land and water use."</blockquote><p>The two DAC technologies included in the study are based on different ways to adsorb CO2 from the air, which are being <a href="http://www.geoengineeringmonitor.org/2019/07/direct-air-capture-recent-developments-and-future-plans/" target="_blank">developed</a> by a number of startup companies around the world.</p><p>One, typically used in larger industrial-scale facilities such as those being piloted by Canadian firm <a href="https://carbonengineering.com/" target="_blank">Carbon Engineering</a>, uses a solution of hydroxide to capture CO2. This mixture must then be heated to high temperatures to release the CO2 so it can be stored and the hydroxide reused. The process uses existing technology and is currently thought to have the lower cost of the two alternatives.</p><p>The second technology uses <a href="https://www.sciencedirect.com/science/article/pii/S2405656116301249" target="_blank">amine adsorbents</a> in small, modular reactors such as those being <a href="https://www.carbonbrief.org/swiss-company-hoping-capture-1-global-co2-emissions-2025" target="_blank">developed</a> by Swiss firm <a href="https://www.climeworks.com/" target="_blank">Climeworks</a>. Costs are currently higher, but the potential for savings is thought to be greater, the paper suggests. This is due to the modular design that could be made on an industrial production line, along with lower temperatures needed to release CO2 for storage, meaning waste heat could be used.</p>
<h4>Delayed Cuts</h4><p>Overall, despite "huge uncertainty" around the cost of DAC, the study suggests its use could allow early cuts in global greenhouse gas emissions to be somewhat delayed, "significantly reduc[ing] climate policy costs" to meet stringent temperature limits.</p><p>Using DAC means that global emissions in 2030 could remain at higher levels, the study says, with much larger use of negative emissions later in the century. This is shown in the charts, below, for scenarios staying below 1.5 C (left panel, shades of blue) and 2 C (right, green).</p><p>Pathways without DAC are shown in darker shades. For example, the solid dark blue line shows results from the "TIAM" model, with emissions peaking around 2020 and falling rapidly to below zero around 2050.</p><p>In contrast, the light blue solid line shows a pathway where DAC allows a more gradual decline, reaching zero in the 2060s and with negative emissions of around 30 billion tonnes per year (Gt/yr) by the 2080s. This is close to today's <a href="https://www.carbonbrief.org/analysis-fossil-fuel-emissions-in-2018-increasing-at-fastest-rate-for-seven-years" target="_blank">annual global emissions</a> of around 40GtCO2/yr.</p>
<img lazy-loadable="true" src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xOTk2Mzk5NS9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYyMTYyNjY1MX0.CHX3JN1iMc9s0RxGY6nhr7ojg7JeSRYWPh1GslBrH78/img.jpg?width=980" id="6fbd3" class="rm-shortcode" data-rm-shortcode-id="539ee15be214e5542832e0d1e03fdc45" data-rm-shortcode-name="rebelmouse-image" />
Global CO2 emissions from fossil fuels (Gt/yr) in model pathways consistent with limiting warming this century to 1.5 C (left panel, blue) or 2 C (right panel, green). Results from two different IAMs – TIAM and WITCH – are shown with solid and dashed lines, respectively. The various lines show scenarios that use direct capture ("DAC," darker shades) and those that do not ("NoDAC," lighter), as well as pathways to 2 C without negative emissions of any sort ("NoNET," darkest green). Source: Realmonte et al. (2019).
<p>"The results of both models are surprisingly similar," says <a href="https://www.carbonbrief.org/noopener" target="_blank">Dr. Nico Bauer</a>, a scientist at the <a href="https://www.carbonbrief.org/noopener" target="_blank">Potsdam Institute for Climate Impacts Research</a> (PIK), who was not involved in the study. He tells Carbon Brief: "This increases the credibility about the main conclusions that the DACCS technology can play an important role in a long-term climate change mitigation strategy."</p><p>The use of DAC in some of the modeled pathways delays the need to cut emissions in certain areas. The paper explains: "DACCS allows a reduction in near term mitigation effort in some energy-intensive sectors that are difficult to decarbonise, such as transport and industry."</p><p>Steve Oldham, chief executive of DAC startup <a href="https://www.carbonbrief.org/noopener" target="_blank">Carbon Engineering</a> says he sees this as the key purpose of CO2 removal technologies, which he likens to other "essential infrastructure" such as waste disposal or sewage treatment.</p><p>Oldham tells Carbon Brief that while standard approaches to cutting CO2 remain essential for the majority of global emissions, the challenge and cost may prove too great in some sectors. He says:</p><p>"DAC and other negative emissions technologies are the right solution once the cost and feasibility becomes too great … I see us as the backstop for challenging abatement."</p>
<h4>Comparing Costs</h4><p>Even though DAC may be relatively expensive, the model pathways in the new study still see it as much cheaper than cutting emissions from these hard-to tackle sectors. This means the models deploy large amounts of DAC, even if its costs are at the high end of current estimates.</p><p>It also means the models see pathways to meeting climate goals that include DAC as having lower costs overall ("reduce[d]… by between 60 to more than 90%"). </p><p>Gambhir tells Carbon Brief: "Deploying DAC means less of a steep mitigation pathway in the near-term, and lowers policy costs, according to the modeled scenarios we use in this study."</p><p>However, the paper also points to the significant challenges associated with such a large-scale, rapid deployment of DAC, in terms of energy use and the need for raw materials.</p><p>The energy needed to run direct air capture machines in 2100 is up to 300 exajoules each year, according to the paper. This is more than half of overall <a href="https://www.carbonbrief.org/in-depth-is-shells-new-climate-scenario-as-radical-as-it-says" target="_blank">global demand today</a>, from all sources, and despite rising demand this century, it would still be a quarter of expected demand in 2100.</p><p>To put it another way, it would be equivalent to the current annual energy demand of <a href="https://www.carbonbrief.org/noopener" target="_blank">China</a>, <a href="https://www.carbonbrief.org/noopener" target="_blank">the U.S</a>., <a href="https://www.carbonbrief.org/noopener" target="_blank">the EU</a> and <a href="https://www.carbonbrief.org/noopener" target="_blank">Japan</a> combined – or the global supply of energy from <a href="https://www.carbonbrief.org/in-depth-bp-data-reveals-record-co2-emissions-in-2018-driven-by-surging-use-of-gas" target="_blank">coal and gas</a> in 2018.</p><p>Gambhir tells Carbon Brief:</p><blockquote>"Large-scale deployment of DAC in below-2°C scenarios will require a lot of heat and electricity and a major manufacturing effort for production of CO2 sorbent. Although DAC will use less resources such as water and land than other NETs [such as BECCS], a proper full life-cycle assessment needs to be carried out to understand all resource implications."</blockquote>
<h4>Deployment Risk</h4><p>There are also questions as to whether this new technology could be rolled out at the speed and scale envisaged, with expansion at up to 30% each year and deployment reaching 30GtCO2/yr towards the end of the century. This is a "huge pace and scale," Gambhir says, with the rate of deployment being a "key sensitivity" in the study results.</p><p><a href="https://www.carbonbrief.org/noopener" target="_blank">Professor Jennifer Wilcox</a>, professor of chemical engineering at <a href="https://www.carbonbrief.org/noopener" target="_blank">Worcester Polytechnic Institute</a>, who was not involved with the research, says that this rate of scale-up warrants caution. She tells Carbon Brief:</p><blockquote>"Is the rate of scale-up even feasible? Typical rules of thumb are increase by an order of magnitude per decade [growth of around 25-30% per year]. [Solar] PV scale-up was higher than this, but mostly due to government incentives … rather than technological advances."</blockquote><p>Reaching 30GtCO2/yr of CO2 capture – a similar scale to current global emissions – would mean building some 30,000 large-scale DAC factories, the paper says. For comparison, there are fewer than 10,000 <a href="https://www.carbonbrief.org/mapped-worlds-coal-power-plants" target="_blank">coal-fired power stations</a> in the world today.</p><p>If DAC were to be carried out using small modular systems, then as many as 30m might be needed by 2100, the paper says. It compares this number to the 73m light vehicles that are built each year.</p><p>The study argues that expanding DAC at such a rapid rate is comparable to the speed with which newer electricity generation technologies such as nuclear, wind and solar have been deployed.</p>
<img lazy-loadable="true" src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xOTk2NDAxNS9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY1MDIwNjI1Mn0.COF4jZ_Nq5GcJA4dPnOhwpthgjtOT6QwgaaGNmnHNxI/img.jpg?width=980" id="a3afb" class="rm-shortcode" data-rm-shortcode-id="6e4b89d89d7e38608e085c53d1512676" data-rm-shortcode-name="rebelmouse-image" />
Climeworks greenhouse © Climeworks / Julia Dunlop
<p>The modeled rate of DAC growth is "breathtaking" but "not in contradiction with the historical experience," Bauer says. This rapid scale-up is also far from the only barrier to DAC adoption.</p><p>The paper explains: "[P]olicy instruments and financial incentives supporting negative emission technologies are almost absent at the global scale, though essential to make NET deployment attractive."</p><p>Carbon Engineering's Oldham agrees that there is a need for policy to recognize negative emissions as unique and different from standard mitigation. But he tells Carbon Brief that he remains "very very confident" in his company's ability to scale up rapidly.</p><p>(The new study includes consideration of the space available to store CO2 underground, finding this not to be a limiting factor for DAC deployment.)</p>
<h4>Breaching Limits</h4><p>The paper says that the challenges to scale-up and deployment on a huge scale bring significant risks, if DAC does not deliver as anticipated in the models. Committing to ramping up DAC rather than cutting emissions could mean locking the energy system into <a href="https://www.ecowatch.com/tag/fossil-fuels" rel="noopener noreferrer">fossil fuels</a>, the authors warn.</p><p>This could risk breaching the Paris temperature limits, the study explains:</p><p>"The risk of assuming that DACCS can be deployed at scale, and finding it to be subsequently unavailable, leads to a global temperature overshoot of up to 0.8°C."</p><p>Gambhir says the risks of such an approach are "too high":</p><p>"Inappropriate interpretations [of our findings] would be that DAC is a panacea and that we should ease near-term mitigation efforts because we can use it later in the century."</p><p>Bauer agrees:</p><p>"Policymakers should not make the mistake to believe that carbon removals could ever neutralise all future emissions that could be produced from fossil fuels that are still underground. Even under pessimistic assumptions about fossil fuel availability, carbon removal cannot and will not fix the problem. There is simply too much low-cost fossil carbon that we could burn."</p><p>Nonetheless, <a href="https://www.eiee.org/team-member/massimo-tavoni/" target="_blank">professor Massimo Tavoni</a>, one of the paper's authors and the director of the <a href="https://www.eiee.org/" target="_blank">European Institute on Economics and the Environment</a> (EIEE), tells Carbon Brief that "it is still important to show the potential of DAC – which the models certainly highlight – but also the many challenges of deploying at the scale required."</p><p>The global carbon cycle poses one final – and underappreciated – challenge to the large-scale use of negative emissions technologies such as DAC: ocean rebound. This is because the amount of CO2 in the world's <a href="http://www.ecowatch.com/tag/oceans" rel="noopener noreferrer">oceans</a> and atmosphere is in a dynamic and <a href="https://twitter.com/RARohde/status/1131224330241806337" target="_blank">constantly shifting equilibrium</a>.</p><p>This equilibrium means that, at present, oceans absorb a <a href="https://www.carbonbrief.org/analysis-fossil-fuel-emissions-in-2018-increasing-at-fastest-rate-for-seven-years" target="_blank">significant proportion</a> of human-caused CO2 emissions each year, reducing the amount staying in the atmosphere. If DAC is used to turn global emissions net-negative, as in the new study, then that equilibrium will also go into reverse.</p><p>As a result, the paper says <a href="https://link.springer.com/article/10.1007/s40641-018-0104-3" target="_blank">as much as a fifth</a> of the CO2 removed using DAC or other negative emissions technologies could be offset by the oceans releasing CO2 back into the atmosphere, reducing their supposed efficacy.</p>
<blockquote class="twitter-tweet"><p lang="en" dir="ltr">"We are in deep trouble." In my 2nd <a href="https://twitter.com/EcoWatch?ref_src=twsrc%5Etfw">@EcoWatch</a> post today, the latest <a href="https://twitter.com/IEA?ref_src=twsrc%5Etfw">@IEA</a> data shows energy-related C02 emissions hit a record high in 2018: <a href="https://t.co/yESL234Q8j">https://t.co/yESL234Q8j</a></p>— Olivia Rosane (@orosane) <a href="https://twitter.com/orosane/status/1110633264866344962?ref_src=twsrc%5Etfw">March 26, 2019</a></blockquote> <script async src="https://platform.twitter.com/widgets.js" charset="utf-8"></script>
<p><em>Reposted with permission from our media associate <a href="https://www.carbonbrief.org/direct-co2-capture-machines-could-use-quarter-global-energy-in-2100" rel="noopener noreferrer" target="_blank">Carbon Brief</a>.</em></p>From Your Site Articles
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Houses damaged by a tornado in Dayton, Ohio on May 28. SETH HERALD / AFP / Getty Images
By Zeke Hausfather
The U.S. has recently experienced one of its worst tornado outbreaks of the past decade, with more than 500 reported over 30 days. The number so far this year is also more than 200 above average.
This has raised the question of what role, if any, climate change may have played in this unusually intensive period of tornadoes. While some have suggested that climate change is driving the above-average numbers, the scientific community has pushed back on these claims.
<p>Scientists have relatively <a href="http://www.nap.edu/catalog/21852/attribution-of-extreme-weather-events-in-the-context-of-climate-change" target="_blank">low confidence</a> in detecting a link between tornado activity and climate change. They cannot exclude the possibility of a link; rather, the science is so uncertain that they simply do not know at this point.</p><p>What is clear is that there is <a href="https://www.ncdc.noaa.gov/swdi/" target="_blank">no observable increase</a> in the number of strong tornadoes in the U.S. over the past few decades. At the same time, tornadoes <a href="https://science.sciencemag.org/content/346/6207/349.full" target="_blank">have become</a> more clustered, with outbreaks of multiple tornadoes becoming more common even as the overall number has remained unchanged. There is also <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018GL080819" target="_blank">evidence</a> that tornado "power" has been increasing in recent years.</p><p><a href="https://www.pnas.org/content/110/41/16361" target="_blank">Some research</a> has suggested that climate change will create conditions more favorable to the formation of severe thunderstorms and tornadoes, but such effects are <a href="https://science.sciencemag.org/content/346/6207/349.full" target="_blank">not detectable</a> in observations today.</p><p>Any role for climate change in affecting the conditions for tornado formation is still very much an open question and the subject of ongoing research by the scientific community.</p>
<h4>Highly Uncertain Attribution</h4><p>Climate change <a href="https://www.carbonbrief.org/mapped-how-climate-change-affects-extreme-weather-around-the-world" target="_blank">affects different extreme weather events</a> in different ways. Some, such as increases in extreme heat events, reductions in extreme cold events, and increases in extreme precipitation events are easy to understand and attribute to a changing climate. Others, such as the <a href="http://www.cimms.ou.edu/~doswell/Monograph/Overview.html" target="_blank">severe convective storms</a> that produce tornadoes, are much more difficult to unpick.</p><p>The figure below shows how well the effects of climate change on different extreme events are understood. It ranks each type of extreme event based on how well the effects of climate change are understood (the x-axis) and on the extent to which any individual event can be attributed to climate change (the y-axis).</p>
<img lazy-loadable="true" src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xOTU3MzEzMi9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY0NTQ3NTY1Mn0.6CbTmIDOGlkG5qDQsA7F0DK4eDPP_ljD7oMRJ-wzUwU/img.jpg?width=980" id="19622" class="rm-shortcode" data-rm-shortcode-id="a3af77b3622809e2fd5aa5fe98fa7b03" data-rm-shortcode-name="rebelmouse-image" />
Understanding and attribution of climate change impacts on extreme events, by event type.
Figure from the U.S. National Academy of Sciences report on the Attribution of Extreme Weather Events published in 2016.
<p>According to this ranking, severe convective storms that produce tornadoes have both the least well understood link to climate change and the lowest confidence in attributing any individual storm (or tornado) to climate change.</p><p>This does not mean that there is definitively no climate link.</p><p><a href="http://geography.uga.edu/directory/people/j-marshall-shepherd" target="_blank">Dr. Marshall Shepherd</a>, a professor at the <a href="http://geography.uga.edu/" target="_blank">University of Georgia</a> and an author of the NAS report, explains in a recent <a href="https://www.forbes.com/sites/marshallshepherd/2019/05/29/climate-change-and-tornadoes-a-succinct-guide-to-what-we-know/#741828d7709c" target="_blank">column in Forbes</a>:</p><p>"It is important to point out that just because an event is low on the scale, that doesn't mean there is no climate change influence; it simply means scientific evidence is not strong enough at this time to draw stronger conclusions."</p><p>As the NAS report points out, there is a much clearer climate link with extreme rainfall. Extreme rainfall <a href="https://nca2014.globalchange.gov/report/our-changing-climate/heavy-downpours-increasing" target="_blank">has already increased</a> over much of the central U.S., potentially contributing to ongoing <a href="https://www.washingtonpost.com/weather/2019/05/30/extreme-weather-is-pummeling-midwest-farmers-are-deep-trouble/?utm_term=.2d41f6082dd7" target="_blank">devastating flooding</a> in the region this year.</p><p>The 2018 <a href="https://nca2018.globalchange.gov/chapter/2/" target="_blank">Fourth National Climate Assessment</a> has similar reservations about any links between climate change and tornadoes. It says:</p><p>"Observed and projected future increases in certain types of <a href="http://www.ecowatch.com/tag/extreme-weather" target="_self">extreme weather</a>, such as heavy rainfall and extreme heat, can be directly linked to a warmer world. Other types of extreme weather, such as tornadoes, hail, and thunderstorms, are also exhibiting changes that may be related to climate change, but scientific understanding is not yet detailed enough to confidently project the direction and magnitude of future change."</p><p>Some of the year-to-year variability in tornado numbers is influenced by <a href="https://www.carbonbrief.org/interactive-much-el-nino-affect-global-temperature" target="_blank">El Niño and La Niña</a> conditions. A <a href="https://journals.ametsoc.org/doi/full/10.1175/JAMC-D-16-0249.1" target="_blank">2017 paper</a> found there are more U.S. tornadoes in La Niña years; however, the current large outbreak is during an El Niño year.</p><p>Other types of natural variability can affect tornado occurrence. For example, <a href="https://journals.ametsoc.org/doi/full/10.1175/MWR-D-18-0207.1" target="_blank">research has suggested</a> that the "<a href="https://www.climate.gov/news-features/blogs/enso/what-mjo-and-why-do-we-care" target="_blank">Madden-Julian oscillation</a>," a periodic swing in temperature and moisture starting in the Indian Ocean, can have a large impact on tornado activity in the U.S. Based on this insight, <a href="https://www.vox.com/2019/5/29/18643166/tornado-2019-ohio-kansas-missouri" target="_blank">scientists predicted</a> in late April that there would be a high likelihood of tornadoes in late May.</p>
<img lazy-loadable="true" src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xOTU3MzEzOC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY1NTgzOTAxM30.QaQcDITjb3abBcd5-5o6t-SLlVjds4c19t_9B-iuvME/img.jpg?width=980" id="0c958" class="rm-shortcode" data-rm-shortcode-id="766326d08797ded00a45244c72dc5e80" data-rm-shortcode-name="rebelmouse-image" />
U.S. tornado tracks by Fujito scale severity (F0-F5) from 1950-2016.
Image from usatornadoes.com.
<p>While the overall number of reported tornadoes in the U.S. has doubled since the 1950s, this statistic is highly misleading. Until the 1990s, tornado records were mostly based on someone spotting a tornado and reporting it to the National Weather Service.</p><p>As most tornadoes are small and last only a few minutes, the number observed and reported will be considerably smaller than the true number that occurred. The increase in tornadoes over time is largely due to the advent of modern "<a href="https://www.weather.gov/mkx/using-radar" target="_blank">Doppler</a>" weather radar systems in the 1990s, which can detect weak tornadoes and those in sparsely populated areas that may previously have gone unreported.</p><p>If weak tornadoes are excluded, there is no detectable trend in tornadoes over the past century. The figure below, based on an analysis of reports in NOAA's <a href="https://www.ncdc.noaa.gov/swdi/" target="_blank">Severe Weather Data Inventory</a> by Carbon Brief, shows the total number of tornadoes in each year, excluding small F0 (or EF0) tornadoes that would likely have been underreported in the past.</p>
<iframe scrolling="no" frameborder="0" marginheight="0px" marginwidth="0px" style="display: initial; margin: 0 auto;" src="https://cbhighcharts2019.s3.eu-west-2.amazonaws.com/Tornadoes/tornadoes.html" width="770px" height="500px"></iframe><span style="display:block; height:22px; max-width:800px;"><a href="https://www.carbonbrief.org"><img src="https://s3.eu-west-2.amazonaws.com/cbhighcharts2019/cb-logo-highcharts.svg" style="width: 22px; height: 22px; margin-top: 2px; margin-bottom: 2px; float:right; background-repeat: no-repeat; background-size: contain;"/></a></span><p>Number of notable (F1+ or EF1+) tornadoes per year between 1950 and 2018. Data from NOAA's <a href="https://www.ncdc.noaa.gov/swdi/" target="_blank">Severe Weather Data Inventory</a>. Chart by Carbon Brief using <a href="https://www.highcharts.com/" target="_blank">Highcharts</a>. </p>
<p>If only the strongest tornadoes are considered (F3-F5 or EF3-EF5), there is even <a href="https://www.washingtonpost.com/news/wonk/wp/2013/05/21/a-short-history-of-violent-tornadoes-in-the-united-states/?utm_term=.2806c1e73abd" target="_blank">weak evidence</a> of a decline in numbers over the past few decades. However, experts <a href="https://www.livescience.com/41632-the-truth-about-tornadoes.html" target="_blank">warn against</a> reading too much into an apparent decline in the number of severe tornadoes. They point out that the rating of strong tornadoes has not been consistent and that "early official records systematically rated tornadoes stronger" than those in the past three decades.</p><h4>More Tornado Clusters</h4><p>While there is little evidence of an increase in the number of tornadoes, there is evidence that the pattern of tornado occurrence has been changing. A 2014 <a href="https://science.sciencemag.org/content/346/6207/349.full" target="_blank">study in Science</a> found that there has been considerably more clustering of tornadoes in recent decades. In other words, there are more days in which multiple tornadoes occur, but fewer overall days with tornadoes.</p><p>The number of days each year with at least one tornado has declined in recent decades, as the chart below shows in black. At the same time, days with more than 30 tornadoes are becoming more frequent (grey).</p>
<img lazy-loadable="true" src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xOTU3MzE0NS9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYxNDIwOTY4M30.uMzOss2Q0mAbvsAFeCesXJMWIRONGdOg6cv7LtHQMPA/img.jpg?width=980" id="67fe7" class="rm-shortcode" data-rm-shortcode-id="496d487388d192f7544eec69c9c8301a" data-rm-shortcode-name="rebelmouse-image" />
Number of days with at least one F1+ tornado (black) and over 30 F1+ tornadoes (grey) between 1950 and 2014.
Figure 4 in Brooks et al 2014.
<p>The authors suggest that this trend is robust, but do not have a good explanation as to why it is occurring. They cannot identify any reason why this behavior would be driven by observed climate changes, but at the same time say they cannot exclude climate change as a factor.</p><p>Other recent research suggests that overall tornado "power" has increased in recent years, once all other environmental variables are accounted for. A <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018GL080819" target="_blank">2018 paper</a> by <a href="http://geography.fsu.edu/people/james-elsner/" target="_blank">Dr. James Elsner</a> and colleagues found a clear upward trend in tornado power of 5.5% per year over the past few decades. However, they caution that "a majority of the trend is not attributable to changes in storm environments."</p><h4>More Common Conditions for Tornadoes?</h4><p>There is limited evidence that tornadoes have become more frequent in recent years. However, a number of climate modeling studies have suggested that conditions favoring the development of severe thunderstorms — and tornadoes — in the U.S. should become more common in the future.</p><p>As the <a href="https://nca2018.globalchange.gov/chapter/2/" target="_blank">Fourth National Climate Assessment</a> reported:</p><p>Modeling studies consistently suggest that the frequency and intensity of severe thunderstorms in the U.S. could increase as climate changes, particularly over the U.S. Midwest and Southern Great Plains during spring. There is some indication that the atmosphere will become more conducive to severe thunderstorm formation and increased intensity, but confidence in the model projections is low. Similarly, there is only low confidence in observations that storms have already become stronger or more frequent. Much of the lack of confidence comes from the difficulty in both monitoring and modeling small-scale and short-lived phenomena.</p><p>A <a href="https://www.pnas.org/content/110/41/16361" target="_blank">2013 paper</a> by <a href="https://woods.stanford.edu/people/noah-diffenbaugh" target="_blank">Dr. Noah Diffenbaugh</a> and colleagues examined how the conditions needed for severe thunderstorms and tornadoes to develop are projected to change in climate models.</p><p>Climate models are too coarse to model individual tornadoes. However, they show a strong increase in conditions favoring severe thunderstorms over the eastern U.S. during spring and autumn months, particularly once global warming exceeds 2°C above preindustrial levels.</p><p><a href="http://whrc.org/staff/jennifer-francis/" target="_blank">Dr. Jennifer Francis</a> at <a href="http://whrc.org/" target="_blank">Woods Hole Research Center</a> in Massachusetts <a href="https://www.newscientist.com/article/2204892-stalled-jet-stream-has-caused-two-weeks-of-tornadoes-in-the-us/" target="_blank">has argued</a> that changes in Arctic sea ice have made ridge patterns in the jet stream more common. In addition, she says that this configuration of the jet stream has played a large role in the current tornado outbreak.</p><p>Other researchers <a href="https://science.sciencemag.org/content/343/6172/729.full" target="_blank">have been more skeptical</a> of the role of changing Arctic conditions in current weather patterns and stress that this is still an area of vigorous scientific debate.</p><p>While scientists cannot exclude a role for climate change in changes in tornado activity, links between the two are still largely speculative, particularly for individual events such as the recent outbreak in the U.S. As Diffenbaugh <a href="https://www.nytimes.com/2018/08/08/climate/tornadoes-climate-change.html" target="_blank">recently told</a> The New York Times:</p><p>"Tornadoes are the kind of extreme event where we have the least confidence in our ability to attribute the odds or characteristics of individual events to an influence of global warming."</p>
<blockquote class="twitter-tweet"><p lang="en" dir="ltr">Our thoughts are with everyone impacted by the devastating tornadoes across the U.S. this past week. 💚 <a href="https://t.co/iHmmXc8KbN">https://t.co/iHmmXc8KbN</a></p>— Greenpeace USA (@greenpeaceusa) <a href="https://twitter.com/greenpeaceusa/status/1133426460335718406?ref_src=twsrc%5Etfw">May 28, 2019</a></blockquote> <script async src="https://platform.twitter.com/widgets.js" charset="utf-8"></script>
<p><em>Reposted with permission from our media associate <a href="https://www.carbonbrief.org/tornadoes-and-climate-change-what-does-the-science-say-2" target="_blank">Carbon Brief</a>.</em></p>From Your Site Articles
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A coal-fired power plant in Jiangxi, China. chuyu / iStock / Getty Images Plus
By Daisy Dunne
The IEA's Coal 2018 report finds that global coal demand grew by 1 percent in 2017 after two years of decline. The rise was chiefly driven by global economic growth, it says. Despite recent growth, demand is still below "peak" levels seen in 2014.
Demand is likely to "remain stable" until 2023, the report authors say. This is because falling demand in western Europe and North America is likely to be offset by increased demand in a host of Asian countries, including India, Indonesia and Vietnam.
Carbon Brief takes a look at the IEA's changing coal forecasts for key world regions.
<p><strong>Plateauing Projections</strong></p><p>Each year, the IEA publishes a series of six-year forecasts for key energy markets. For example, the Coal 2018 report looks at the market for the <a href="https://www.ecowatch.com/tag/fossil-fuels">fossil fuel</a> out to 2023, broken down by country and sector.</p><p>This year's report leads with the news that global coal demand returned to growth in 2017 after two years of decline. It is likely that demand will continue to grow in 2018, said <a href="https://www.iea.org/about/leadership/" target="_blank">Keisuke Sadamori</a>, director of energy markets and security at the IEA. He told a press briefing:</p><blockquote>"The global coal demand declined in 2015 and 2016. In 2017, it rebounded, and our estimates suggest it will grow in 2018 too. However, this is very different to the growth we saw earlier in the decade."</blockquote><p>In other words, global coal demand is growing, but is still below "peak" levels seen in 2014. Actual demand is shown in red on the chart below, with each year's IEA forecast shown in shades of blue. (Note that the y-axis does not start at zero.)</p>
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<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xOTAxMjAwMC9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTY1MzcxMDc0Nn0.axTFCginGk0nXJbkJduSSbATgXNSC2jAv5MBb1gJVAQ/img.png?width=980" id="22f2b" class="rm-shortcode" data-rm-shortcode-id="9ea2f0a83fe74b6c7b7fdda4e7f721c6" data-rm-shortcode-name="rebelmouse-image">
</p>
<p>The further expected increase to demand in 2018 is thought to be "driven by strong coal power generation in <a href="https://www.ecowatch.com/tag/china">China</a> and India," the report says.<br></p><p>The chart also shows how, in 2016, global coal demand fell to a level lower than expected by the IEA's projections.</p><p>This year's six-year forecast is the first to project a small decline in global coal demand by 2021—suggesting IEA is moving away from forecasting ongoing growth in demand.</p><p>The change in forecast reflects the fact that "we are in a different world" to when the IEA made its first coal projections in 2011, said <a href="http://www.coaltrans.com/world-coal-conference/speaker-details/a0rd000000i4swumaf/carlos-fernandez-alvarez.html" target="_blank">Carlos Fernández Alvarez</a>, a senior energy analyst at the IEA. He told Carbon Brief:</p><blockquote>"In 2011, the big question about coal was when Chinese coal consumption would peak. Given the sheer size of China and of Chinese growth, this meant that the world's coal consumption would also grow. Now, we are in a different world. Not only owing to changes in China, but many other things have happened in the meantime, such as the shale revolution, the renewable costs decline and the Paris Agreement—so our forecast has also changed."</blockquote><p><strong>'Two Europes'</strong></p><p>The projected plateau and slow decline of global demand in the coming years is partly the result of efforts to move away from coal in western Europe and North America, the authors say.</p><p>The map below, which is taken from page 89 of the report, gives an idea of how coal phase-out plans currently look across Europe.</p><p>On the map, light green shows countries that have no coal power plants, dark green shows out where phase-out has been planned for 2020-30, orange shows where a phase-out has been discussed and scarlet is used for countries with no phase-out policy.</p>
<p class="shortcode-media shortcode-media-rebelmouse-image">
<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xOTAxMjAwNC9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTYwNzU0NDI5M30._mvSN-N2Sg6SYuEjqK6p6kQVRkPejPGPDpN-6JTchvM/img.png?width=980" id="2d34f" class="rm-shortcode" data-rm-shortcode-id="7574d6f2ddad9d4e83c8a58e241b724e" data-rm-shortcode-name="rebelmouse-image">
<small class="image-media media-caption" placeholder="add caption...">Differences in coal phase-out policy in countries across Europe. Light green shows countries that have no coal power plants, dark green shows where phase-out has been planned for 2020-30, orange shows where a phase-out has been discussed and scarlet is used for countries with no phase-out policy</small><small class="image-media media-photo-credit" placeholder="add photo credit..."><a href="https://www.iea.org/coal2018" target="_blank">Coal 2018, IEA</a></small></p>
<p>The map paints a picture of "two Europes," the report says. In western Europe, specific policies for a coal phase out combined with action on <a href="https://www.ecowatch.com/tag/climate-change">climate change</a>, including through the <a href="https://www.carbonbrief.org/qa-will-reformed-eu-emissions-trading-system-raise-carbon-prices" target="_blank">EU Emissions Trading System</a>, is likely to hit coal demand hard, the report says:<br></p><blockquote>"By 2023, at least two more countries, France and Sweden, will have closed their last coal power plants, and Germany will be the only significant coal consumer remaining in western Europe."</blockquote><p>Across the EU, coal consumption declined by 1.1 percent to 627m tonnes in 2017. Consumption of thermal coal—which is used in power generation—dropped by a sharp 7 percent from 2016 to 188m tonnes, while coking coal—which is used in steel production—remained flat. Lignite use for power generation increased 2 percent to 381m tonnes.</p><p>However, in eastern Europe—where coal demand remains level—most countries have not announced phase-out policies, the report says, and new coal power plants are <a href="https://www.carbonbrief.org/mapped-worlds-coal-power-plants" target="_blank">under construction</a> in the Balkans, Greece and Poland.</p><p>The report projects that, in the EU, coal demand will drop 2.5 percent per year, from 325m tonnes of coal equivalent (mtce) in 2017 to 280 mtce in 2023. (Coal equivalent is a standardized measure of the energy obtained from burning coal.)</p><p>By this point, it will have taken 30 years for coal consumption to drop by half, the report notes, "indicating the resiliency of coal as an energy resource."</p><p>Looking across the whole of Europe, however, brings a different forecast. Coal demand is expected to fall at a rate of 1.3 percent—owing to demand remaining stable in eastern Europe and potentially increasing in Turkey, the report says.</p><p>In the U.S., coal demand dropped by 2.6 percent to 641m tonnes in 2017. However, this decline is less rapid than in the last two years, likely reflecting a slow-down in the closure of coal power stations, the report says. Coal retirements have returned to <a href="https://about.bnef.com/blog/u-s-coal-plant-retirements-near-all-time-high/" target="_blank">near-record levels</a> in 2018.</p><p><strong>Blue-Sky Thinking</strong></p><p>In China, the world's largest coal producer, demand rose by 10m tonnes to 3,664m tonnes in 2017, following three years of decline. This rise was largely fueled by an increase in coal-fired power generation, the report says.</p><p>However, the IEA projects a decline in coal demand to 2,673 mtce by 2023. This is owed to expected declines of coal consumption by key industries, such as <a href="https://www.carbonbrief.org/qa-how-will-chinas-new-carbon-trading-scheme-work" target="_blank">steel</a>.</p><p>Another expected driver of falling demand in China is the country's "<a href="https://www.chinadialogue.net/article/show/single/en/10711-China-releases-2-2-action-plan-for-air-pollution" target="_blank">Blue Sky</a>" policy—an action plan for cutting <a href="http://www.ecowatch.com/tag/air-pollution">air pollution</a> across large cities. The policy has seen several cities, including Beijing, <a href="https://www.chinadialogue.net/article/show/single/en/10711-China-releases-2-2-action-plan-for-air-pollution" target="_blank">introduce bans</a> on residents burning coal for heat. The report says:</p><blockquote>"Environmental policies, and in particular clean-air measures, constrain coal demand. The main target of the policy action is to reduce direct coal use and <a href="https://www.bloomberg.com/news/articles/2017-12-10/freezing-cities-force-china-to-ease-anti-pollution-curbs-on-coal" target="_blank">small boilers</a> in residential heating, as well as in the commercial and industrial sectors. Cement, steel and small power producers are also targeted in China's air-quality campaign."</blockquote><p>These measures, along with China's commitment to investing in <a href="https://www.carbonbrief.org/china-leading-worlds-clean-energy-investment-says-report" target="_blank">renewable energy and energy efficiency</a>, led the IEA to project an overall decline in demand in China—despite the growth seen in 2017. The report says:</p><blockquote>"Considering all these moving pieces, we maintain the forecast in <a href="https://www.carbonbrief.org/iea-world-coal-demand-will-rise-despite-slashing-growth-india" target="_blank">last year's report</a> that China's coal demand has entered a slow but structural decline at less than 1% per year on average."</blockquote><p><strong>Changing Asia</strong></p><p>The world's greatest percentage increase in coal power demand (5.4 percent) is expected to occur in Southeast Asia—where demand is projected to rise from 186 mtce in 2017 to 259 mtce in 2023.</p><p>Demand growth is expected to be highest in Indonesia, Vietnam, Malaysia and the Philippines, the report says:</p><blockquote>"Although these countries differ considerably in energy resource endowment, they share robust economic growth, a rising population and an expanding middle class, all of which boost power demand. As coal-based power is expected to cover a significant share of the additional demand … considerable new coal-fired capacity is set to come online in these four countries."</blockquote><p>In India, demand is expected to rise from 563 mtce in 2017 to 708 mtce in 2023. The chief driver of this demand is a growing desire for coal-fired power, fueled by ongoing infrastructure development and the expansion of the country's middle class, the report says.</p><p>Coal demand in India is also expected to grow as a result of expansion in key industries, such as <a href="https://www.carbonbrief.org/qa-why-cement-emissions-matter-for-climate-change" target="_blank">cement</a> and <a href="https://www.sciencedirect.com/topics/materials-science/sponge-iron" target="_blank">sponge iron</a> production. By 2023, India's non-power coal consumption is expected to rise by 33 mtce to 163 mtce.</p><p>However, demand is expected to rise more slowly than in the previous decade, the report says. This is largely down to investment in <a href="http://www.ecowatch.com/renewable-energy/">renewable</a> sources of power, the report says.</p><p>The IEA expects the proportion of electricity from renewable sources to double to 25 percent of the total power mix by 2023. The Indian government is aiming to install 100 gigawatts (GW) of <a href="http://www.ecowatch.com/tag/solar">solar</a> by 2022 and 50GW of <a href="http://www.ecowatch.com/tag/wind">wind</a>—double the wind capacity of 2017 and four times the solar capacity. The report says:</p><blockquote>"The large-scale ongoing renewable expansion and the use of <a href="https://reneweconomy.com.au/how-much-do-ultra-supercritical-coal-plants-really-reduce-air-pollution-70678/" target="_blank">supercritical technology</a> in new coal power plants will slow coal demand growth, which will grow by less than 4% per year through 2023, compared to over 6% on average per year in the past decade."</blockquote><p>In addition to growing more slowly than in the recent past, India's coal demand has fallen short of earlier IEA forecasts. This year, the IEA has once again cut its forecast for coal demand growth in India.</p>
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</p><div id="1a0ee" class="rm-shortcode" data-rm-shortcode-id="ECZRPE1576661966"><blockquote class="twitter-tweet twitter-custom-tweet" data-twitter-tweet-id="968225605597696001" data-partner="rebelmouse"><div style="margin:1em 0">World's Largest Coal Miner Says It's a 'Matter of Time' for Renewables to Replace Coal https://t.co/H27q16RWT1… https://t.co/wj1kOI59f2</div> — EcoWatch (@EcoWatch)<a href="https://twitter.com/EcoWatch/statuses/968225605597696001">1519677947.0</a></blockquote></div>
<p></p>
<p><em>Reposted with permission from our media associate <a href="https://www.carbonbrief.org/iea-china-and-india-to-fuel-further-rise-in-global-coal-demand-in-2018" target="_blank">Carbon Brief</a>.</em><br></p>
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A polar bear stands on an ice floe off the northern shores of the Svalbard Archipelago. Chase Dekker Wild-Life Images / Getty Images
By Robert McSweeney
Arctic sea ice has reached its summer minimum extent for the year, clocking in at 4.59m square kilometers (sq km) (approximately 1.77m square miles), which puts it joint sixth lowest in the 40-year satellite record alongside 2008 and 2010.
The twelve smallest summer lows in the satellite record have all occurred in the last twelve years.
<p>The <a href="http://nsidc.org/arcticseaicenews/2018/09/arctic-sea-ice-extent-arrives-at-its-minimum/" target="_blank">announcement</a>, from the National Snow and Ice Data Center (<a href="http://nsidc.org/" target="_blank">NSIDC</a>) in the U.S., is provisional as "changing winds or late-season melt could still reduce the Arctic ice extent."</p><p><strong>Melt Season</strong></p><p>As the northern hemisphere summer comes to an end, the annual retreat of <a href="http://www.ecowatch.com/tag/arctic">Arctic</a> sea ice slows to a stop before ice starts accumulating again. This point is marked each year as the summer minimum, and used as an indicator for the health of Arctic sea ice.</p><p>The 2018 summer low is the joint sixth smallest on record, beaten only by 2015 in fifth, 2011 in fourth, 2007 and 2016 in joint second, and 2012 in first with a record low of 3.39 sq km. The 2018 figure is 1.63m sq km below the average summer minimum for 1981-2010.</p><p>The chart below shows how 2018 (blue line) compares with the previous four years, the record summer of 2012 (brown dotted line), and the long-term average (grey line).</p>
<p class="shortcode-media shortcode-media-rebelmouse-image">
<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xODY3MjQ4MC9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTY0ODgzNDc4NX0.tdJEDdj5cUd38dtPaUk0b0mNt2oUI4PVeglOxMyoItk/img.png?width=980" id="1bcd7" class="rm-shortcode" data-rm-shortcode-id="1fee540d277b2cdba24cdd5a965f2825" data-rm-shortcode-name="rebelmouse-image">
<small class="image-media media-caption" placeholder="add caption...">Arctic sea ice extent up to Sept. 23 2018, along with daily ice extent data for four previous years and the record low year (2012). The 1981-2010 median is in dark grey, and the grey areas around the median line show the interquartile and interdecile ranges.</small><small class="image-media media-photo-credit" placeholder="add photo credit..."><a href="http://nsidc.org/arcticseaicenews/2018/09/arctic-sea-ice-extent-arrives-at-its-minimum/" target="_blank">NSIDC</a></small></p>
<p>Satellite data show that Arctic sea ice hit its minimum on two dates this year—Sept. 19 and Sept. 23. The latter is one of the latest dates for the summer low in the satellite record and around five to nine days later than the 1981-2010 average.<br></p><p>The NSIDC said the lateness was "at least partially caused by southerly winds from the East Siberian Sea, which brought warm air into the region and prevented ice from drifting or growing southward."</p><p>While this year isn't record-breaking, it is still cause for concern, said <a href="http://www.ucl.ac.uk/earth-sciences/people/staff/academic/stroeve" target="_blank">professor Julienne Stroeve</a>, professor of polar observation and modeling at <a href="https://www.ucl.ac.uk/" target="_blank">University College London</a>, senior research scientist at the NSIDC, and member of the <a href="https://www.facebook.com/ArcticDavos/" target="_blank">Arctic Basecamp</a> consortium. She told Carbon Brief:</p><blockquote>"Put simply, in the last ten years the Arctic is melting faster than it ever has previously since records began. We have lost over half of the summer sea ice coverage since the late 1970's and it is realistic to expect an ice-free Arctic sea in summer in the next few decades."</blockquote><p><strong>Cool and Cloudy</strong></p><p>The summer melt season kicked off at the end of March after reaching the <a href="https://www.carbonbrief.org/arctic-sea-ice-hits-second-lowest-winter-peak-on-record" target="_blank">second-lowest winter maximum</a> on record. Sea ice extent remained low through spring, with the average extent in April tied with 2016 as the <a href="http://nsidc.org/arcticseaicenews/2018/05/arctic-winter-warms-up-to-a-low-summer-ice-season/" target="_blank">lowest on record</a> and the average for May being the <a href="http://nsidc.org/arcticseaicenews/2018/06/springtime-for-the-arctic/" target="_blank">second lowest</a> on record.</p><p>Spring saw some unusually warm temperatures in parts of the Arctic—temperatures for the month of May in Svalbard, for example, were 6°C higher than average.</p><p>However, cooler and windier conditions from June onwards saw the pace of sea ice melt slow, despite short periods of rapid decline. This is reflected in the average extents for June, July and August, which clocked in as the <a href="http://nsidc.org/arcticseaicenews/2018/07/a-sluggish-june/" target="_blank">fourth</a>, <a href="http://nsidc.org/arcticseaicenews/2018/08/ice-loss-speeds-up-during-second-half-of-july/" target="_blank">ninth</a> and <a href="http://nsidc.org/arcticseaicenews/2018/09/no-endless-summer-in-the-arctic/" target="_blank">seventh</a> lowest on record, respectively.</p><p>The weather over the Arctic during the summer has been dominated by low pressure, explained <a href="http://sites.uci.edu/zlabe/" target="_blank">Zack Labe</a>, a <a href="https://uci.edu/" target="_blank">University of California, Irvine</a> Ph.D. student studying sea ice. This meant a "tendency toward cooler and cloudier weather" over the summer months.</p><p>The <a href="https://www.ncdc.noaa.gov/teleconnections/ao/" target="_blank">Arctic Oscillation</a> (AO) has also had an impact, said Labe. The AO is a natural climate pattern characterized by westerly winds circulating around the Arctic. When the AO is positive—as it predominantly has been <a href="http://www.cpc.noaa.gov/products/precip/CWlink/daily_ao_index/teleconnections.shtml" target="_blank">from June to September</a>—the winds tend to be stronger, holding cold air over the Arctic.</p><p>This "is generally a favourable weather pattern for less sea ice export and melt during the summer," said Labe. It also contributed to an unusual summer for the Atlantic side of the Arctic, he added:</p><p>"The movement of ice, due to the positive Arctic Oscillation, favoured less sea ice exporting into the Atlantic. This contributed to unusually low sea ice in this region, especially in the Greenland Sea. Also, sea ice around Svalbard has been near record lows for the last few months."</p><p>The map below shows how sea ice on Sept. 23 (shaded white) compares to the average position at that time of the year (orange line).</p>
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<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xODY3MjQ5NS9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTYzMDg5MDg2OH0.jX0Di1d4s294uVk6K34gXJEeCZ3T2yKQzAzSvlLe3F0/img.png?width=980" id="edd90" class="rm-shortcode" data-rm-shortcode-id="c3f1ee3f3a45182359ef1a3c0c3c5252" data-rm-shortcode-name="rebelmouse-image">
<small class="image-media media-caption" placeholder="add caption...">Arctic sea ice extent on Sept. 23, 2018. The orange line shows the 1981-2010 average extent for that day.</small><small class="image-media media-photo-credit" placeholder="add photo credit..."><a href="http://nsidc.org/arcticseaicenews/2018/09/arctic-sea-ice-extent-arrives-at-its-minimum/" target="_blank">NSIDC</a></small></p>
<p><strong>Thickness</strong><br></p><p>Simulations of Arctic sea ice thickness from the <a href="http://psc.apl.uw.edu/research/projects/arctic-sea-ice-volume-anomaly/" target="_blank">University of Washington's PIOMAS model</a> suggest that this summer's average thickness is also close to the long-term declining trend, said Labe:</p><blockquote>"Sea ice is much thinner than average around Greenland, where typically the thickest ice of the Arctic is found. Overall, nearly the entire Arctic Ocean is thinner than the 1981-2010 average."</blockquote><p>This is illustrated in the maps below, which show the estimated thickness of Arctic sea ice in August 2018 (left) and how that compares to the 1981-2010 average (right). The dark blue shading in the right-hand map shows areas where ice is as much as two meters (approximately 6.6 feet) thinner than average for this time of year.</p>
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<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xODY3MjUwMS9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTY0ODcwODc1N30.EKp072JLFazoUGwYHuN05zGTgdq9-0EwpjfWdz2r1QE/img.png?width=980" id="528db" class="rm-shortcode" data-rm-shortcode-id="8a68f9ce02c5242d46e5a2e733f6acf8" data-rm-shortcode-name="rebelmouse-image">
<small class="image-media media-caption" placeholder="add caption...">Current simulated (<a href="http://psc.apl.uw.edu/research/projects/arctic-sea-ice-volume-anomaly/" target="_blank">PIOMAS</a>; Zhang and Rothrock, 2003) sea ice thickness (left) and anomalies relative to a 1981-2010 baseline (right) for August 2018.</small><small class="image-media media-photo-credit" placeholder="add photo credit..."><a href="http://sites.uci.edu/zlabe/arctic-sea-ice-volumethickness/" target="_blank">Zack Labe</a></small></p>
<p>Both Arctic sea ice thickness and extent are continuing on the steady descent seen over the last four decades, said Labe. This is down to a <a href="https://www.carbonbrief.org/humans-causing-up-to-two-thirds-arctic-summer-sea-ice-loss-study-confirms" target="_blank">combination</a> of natural variability and human-caused warming.<br></p><p>But even with relatively cool conditions for some of this summer, sea ice extent still dropped below 5m sq km, noted Labe:</p><blockquote>"This is probably a result of the long-term loss of multi-year, thicker ice leaving the Arctic a very different place than 30 years ago. Unfortunately, these dramatic changes are now happening in all seasons."</blockquote><p>As <a href="https://www.carbonbrief.org" target="_blank">Carbon Brief</a> reported in its "<a href="https://www.carbonbrief.org/state-of-the-climate-2018-set-to-be-fourth-warmest-year-despite-cooler-start" target="_blank">State of the Climate</a>" analysis in August, 2018 has seen record low amounts of "multiyear ice"—ice that has survived without melting for multiple years. In the first half of 2018, multiyear ice comprised <a href="https://www.climate.gov/news-features/featured-images/old-sea-ice-continues-disappearing-arctic-ocean-0" target="_blank">just 34 percent</a> of Arctic sea ice, with only 2 percent at least five years old. In the 1980s, upwards of <a href="https://www.climate.gov/news-features/featured-images/old-sea-ice-continues-disappearing-arctic-ocean-0" target="_blank">60 percent</a> of Arctic sea ice was multiyear ice.</p><p>The lack of multi-year ice is even affecting how scientists carry out their fieldwork, added Stroeve:</p><blockquote>"For us to conduct our experiments and measure Arctic changes effectively, we need to be able to deploy our instruments on mature, multi-year ice so that they have a chance to survive at least one year. This sort of ice is harder and harder to find and we are moving further north to find it. For us scientists, we might need to think about redesigning our instruments to cope with the rapid changes we are witnessing."</blockquote>
<p class="shortcode-media shortcode-media-twitter_embed">
</p><div id="6504c" class="rm-shortcode" data-rm-shortcode-id="M6ZD2B1576662439"><blockquote class="twitter-tweet twitter-custom-tweet" data-twitter-tweet-id="978812687760220161" data-partner="rebelmouse"><div style="margin:1em 0">Arctic Sea Ice Hits Second-Lowest Winter Peak on Record https://t.co/eY6Vp1ixjE @tcktcktck @envirowire</div> — EcoWatch (@EcoWatch)<a href="https://twitter.com/EcoWatch/statuses/978812687760220161">1522202104.0</a></blockquote></div>
<p></p>
<p><em>Reposted with permission from our media associate <a href="https://www.carbonbrief.org/arctic-sea-ice-summer-minimum-in-2018-is-sixth-lowest-on-record" target="_blank">Carbon Brief</a>.</em><br></p>
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Limiting Warming to 2°C Would Prevent ‘Worldwide Increases’ in Heat-Related Deaths
13 September 2018
Climate
A pedestrian uses an umbrella on a hot morning in Los Angeles, CA on Oct. 24, 2017. FREDERIC J. BROWN / AFP / Getty Images
By Daisy Dunne
Restricting global warming to 2°C above pre-industrial levels would prevent large increases in temperature-related deaths across much of the globe, a new study finds.
And keeping warming to 1.5°C—the aspirational target of the Paris agreement—would further limit the number of people dying from temperature extremes in some parts of the world, including in southeast Asia and southern Europe.
<p>However, in some countries with a cooler climate, such as the UK, Ireland and Japan, overall temperature-related deaths would be higher at 1.5°C of warming than 2°C. This is because the additional 0.5°C of warming is expected to bring a bigger drop in winter deaths than the increase in deaths in hot summers, the researchers say.</p><p>The findings—which draw on data taken from 451 locations in 23 countries—show that, overall, taking steps to meet the 1.5°C limit could prevent "a hell of a lot of people" from dying as a result of temperature extremes in tropical countries, a study author tells <a href="https://www.carbonbrief.org" target="_blank">Carbon Brief</a>.</p><p><strong>Heating Up</strong></p><p><a href="https://www.ecowatch.com/tag/climate-change">Climate change</a> is likely to increase both the frequency and severity of heatwaves—such as this <a href="https://www.carbonbrief.org/media-reaction-2018-summer-heatwaves-and-climate-change" target="_blank">summer's record-breaking run of hot weather</a>, <a href="https://www.carbonbrief.org/mapped-how-climate-change-affects-extreme-weather-around-the-world" target="_blank">research</a> shows.</p><p>During a heatwave, the number of "<a href="https://www.carbonbrief.org/study-links-heatwave-deaths-london-paris-climate-change" target="_blank">heat-related deaths</a>"—whereby exposure to heat either causes or significantly contributes to a death—tends to increase. For example, <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3786924/" target="_blank">research</a> shows that, during a heatwave, the risk of death from a heart attack is higher. Heatwaves are also associated with <a href="https://www.publichealthjrnl.com/article/S0033-3506(18)30213-0/fulltext" target="_blank">increased rates of suicide</a>.</p><p>However, <a href="https://www.thelancet.com/journals/lanplh/article/PIIS2542-5196(17)30156-0/fulltext" target="_blank">research</a> also suggests that, as temperatures warm, numbers of "<a href="http://www.realclimate.org/index.php/archives/2018/06/will-climate-change-bring-benefits-from-reduced-cold-related-mortality-insights-from-the-latest-epidemiological-research/" target="_blank">cold-related</a>" deaths—which are caused by exposure to cold weather and winter illnesses—could decrease in some regions. Whether or not this "<a href="http://www.realclimate.org/index.php/archives/2018/06/will-climate-change-bring-benefits-from-reduced-cold-related-mortality-insights-from-the-latest-epidemiological-research/" target="_blank">cold effect</a>" could partially offset the expected rise in heat-related deaths has long been <a href="https://www.carbonbrief.org/explainer-will-rising-temperatures-mean-more-lives-are-saved-than-lost" target="_blank">debated by scientists</a>.</p><p>The new study, published in <a href="https://doi.org/10.1007/s10584-018-2274-3" target="_blank">Climatic Change Letters</a>, seeks to solve this conundrum by comparing the expected number of heat- and cold-related deaths in 23 countries under different levels of global warming.</p><p>To do this, they subtracted the expected fall in cold-related deaths from the expected rise in heat-related deaths for each country. This gave them an overall measure of how warming is likely to affect the number of "temperature-related" deaths.</p><p>The results show that, in many world regions, the number of temperature-related deaths is expected to "significantly increase"—despite decreases in cold-related deaths—if warming is not limited to 2°C. In their research paper, the authors say:</p><blockquote>"Our results suggest that limiting warming below 2C could prevent large increases in temperature-related mortality in most regions worldwide."</blockquote><p>For some regions, limiting warming to 1.5°C rather than 2°C would further prevent a rise in temperature-related deaths, says study author <a href="http://www.bristol.ac.uk/geography/people/dann-m-mitchell/index.html" target="_blank">Dr. Dann Mitchell</a>, a researcher in climate change and health from the <a href="http://www.bristol.ac.uk/" target="_blank">University of Bristol</a>. He told Carbon Brief:</p><blockquote>"One major point from the study is that southeast Asia is the region that will be most severely hit by a net increase in deaths under higher levels of warming. Vietnam, in particular, is expected to experience a 2% increase in net deaths under 2C of warming, rather than 1.5C. That 2% is going to be a hell of a lot of people."</blockquote><p><strong>Divided World<br></strong></p><p>For the study, the researchers used data from the <a href="http://mccstudy.lshtm.ac.uk/" target="_blank">Multi-Country Multi-City Collaborative Research Network</a>—which details the historical relationship between temperature and mortality in 451 locations across 23 countries.</p><p>This information was used to inform a set of <a href="https://www.carbonbrief.org/qa-how-do-climate-models-work" target="_blank">global climate models</a>—which produced projections of temperature-related mortality under 1.5°C, 2°C, 3°C and 4°C of global warming.</p><p>The models assumed that the current wealth and population of each country remained the same under future levels of global warming.</p><p>Under high levels of global warming, temperature-related mortality is likely to increase overall in many regions, the authors say:</p><blockquote>"Under more extreme scenarios, most regions could experience considerably larger heat-mortality risks that would not be balanced by the projected decreases in cold-related excess mortality."</blockquote><p>For example, under 4°C of warming, populations in southern parts of Europe and east Asia are projected to experience a 4-9 percent increase in heat-related deaths when compared to 1.5°C.</p><p>However, when looking at the difference in temperature-related deaths between 1.5 and 2°C, the picture is more "mixed," the researchers say.</p><p>The chart below shows the expected difference in temperature-related deaths between the 1.5 and 2°C scenarios. On the chart, red shows the expected increase in heat-related deaths for each country, blue shows the expected decrease in cold-related deaths and black diamonds mark the overall "net" number of deaths.</p><p>(If a diamond is on the right-hand side of the chart, it means the net number of deaths is expected to be lower under 1.5 than 2°C. However, if it is on the left-hand side, it shows that the net number of deaths is expected to be higher under 1.5 than 2°C for that country.)</p>
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<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xODYwNzY0OC9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTY0NjM1NjkxOX0.WL7Iur7865S7RvaufpYq-fBKOijhLTe9F0YyHFjkec4/img.png?width=980" id="2bd0c" class="rm-shortcode" data-rm-shortcode-id="dc2d4d61edfbda8f3aa6845a66c6bae4" data-rm-shortcode-name="rebelmouse-image">
<small class="image-media media-caption" placeholder="add caption...">Expected difference in temperature-related deaths between scenarios of 1.5 and 2°C of global warming above pre-industrial levels for 23 countries</small><small class="image-media media-photo-credit" placeholder="add photo credit...">Vicedo-Cabrera et al. (2018)</small></p>
<p>The results show how the number of temperature-related deaths in southeast Asia, such as the Philippines, Thailand and Vietnam, and in southern Europe, such as Italy and Spain, would be smaller under 1.5 than 2°C.<br></p><p>For Vietnam, the number of heat-related deaths is expected to be around 2 percent lower under 1.5°C in comparison to 2°C. For Italy and Spain, the number of heat-related deaths is expected to be around 1 percent lower.</p><p>However, in some cooler regions, including in the UK, Ireland and Japan, the net number of deaths is expected to be higher under 1.5 than 2°C. This is because, in these regions, the additional 0.5°C of warming reduces more cold-related deaths than it increases heat-related ones.</p><p>In the UK, the net number of deaths is expected to be around 0.25 percent higher under 1.5°C than 2°C. In Ireland, the net number of deaths could be around 0.5 percent higher under 1.5°C.</p><p>The amount of regional warming is also important. For example, in Australia, the number of heat-related deaths is expected to be smaller than in other parts of Asia because temperature increases are expected to be milder, the researchers say.</p><p>In their research paper, however, the researchers caution that many of their results come with a large degree of statistical uncertainty (shown with black lines on the chart). The authors said:</p><blockquote>"We also observe a large uncertainty in our estimates, particularly those for the next impacts and more extreme scenarios."</blockquote><p>This uncertainty stems from variability in the climate models and a lack of data availability in some regions, they say.</p><p><strong>Vulnerable Hotspots</strong></p><p>Although not all regions would see fewer temperature-related deaths under 1.5°C than 2°C, this does not mean than 2°C should be considered a "safe" temperature limit, the researchers say.</p><p>One reason for this is that some regions that are expected to be the most vulnerable to heat-related deaths, such as southeast Asia, are also the least likely to be able to adapt to climate change, the researchers said:</p><blockquote>"These regions include the most populated areas worldwide and, in general, the most vulnerable to climate change, with a limited capacity for adaptation due to lack of infrastructural, financial and technological resources."</blockquote><p>In addition, comparing cold- and heat-related deaths may not give "the full picture" of how climate change will impact mortality, Mitchell said:</p><blockquote>"Heat-related deaths tend to be very fast, caused by factors such as heart failure, or linked to social factors, such as suicide. On the other hand, cold-snaps lead to a very different sort of mortality. People who die from cold-related deaths can spend two to three weeks in hospital."</blockquote><p>The differences between cold- and heat-related deaths mean they require different types of healthcare, Mitchell says. Because of this, the costs incurred from heat-related deaths may not be offset by a reduction in cold-related deaths. He said:</p><blockquote>"The next stage of our research will be to look at the two metrics separately."</blockquote>
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</p><div id="ef954" class="rm-shortcode" data-rm-shortcode-id="TQ1ICD1576663013"><blockquote class="twitter-tweet twitter-custom-tweet" data-twitter-tweet-id="923728481753628674" data-partner="rebelmouse"><div style="margin:1em 0">Record-Melting Fall Heat Wave Bakes Southern California https://t.co/VzjWlYqDgt @worldresources @tcktcktck</div> — EcoWatch (@EcoWatch)<a href="https://twitter.com/EcoWatch/statuses/923728481753628674">1509069006.0</a></blockquote></div>
<p></p>
<p><em>Reposted with permission from our media associate <a href="https://www.carbonbrief.org/limiting-warming-to-2c-would-prevent-worldwide-increases-in-heat-related-deaths" target="_blank">Carbon Brief</a>.</em><br></p>
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Erosion in a Derbyshire, UK valley by the northern escarpment of Kinder Scout. Stephen Thompson / Bend in the River Ashop / CC BY-SA 2.0
By Daisy Dunne
The UK could cut its emissions to "net-zero" within the next three decades by stepping up investment into technologies that can remove CO2 from the atmosphere, a report finds.
However, such methods, which are known collectively as "negative emissions technologies" (NETs), would only be effective if paired with drastic efforts to cut the UK's current rate of emissions, the findings suggest.
<p>The <a href="https://www.raeng.org.uk/news/news-releases/2018/september/greenhouse-gas-removal-could-make-the-uk-carbon-ne" target="_blank">report</a>, published jointly by the Royal Society and the Royal Academy of Engineering, evaluates how the UK could capitalize on a range of proposed techniques from "<a href="https://www.carbonbrief.org/analysis-how-natural-climate-solutions-can-reduce-the-need-for-beccs" target="_blank">natural climate solutions</a>," such as planting <a href="https://www.ecowatch.com/tag/forests">forests</a>, to more experimental methods, including capturing CO2 directly from the air.</p><p>The findings show that the UK "must act quickly" to ramp up "research and investigation" into a suite of NETs, the report's chair told <a href="https://www.carbonbrief.org/" target="_blank">Carbon Brief</a> at a press briefing in London.</p><p><strong>Hitting Zero</strong></p><p>Under the <a href="http://www.ecowatch.com/tag/paris-agreement">Paris agreement</a>, countries pledged to limit <a href="https://www.ecowatch.com/tag/climate-change">global warming</a> to "well below" 2°C above pre-industrial levels by the end of the century.</p><p>To keep to this limit, countries will collectively need to reach "net-zero" emissions—a scenario where the total amount of greenhouse gases released into the atmosphere is balanced by the total amount taken out—by sometime in the second half of this century.</p><p>For the UK to achieve such a target, it will need to "prioritise rapid cuts in greenhouse gas emissions"—largely through the adoption of low-carbon sources of energy, construction and food production, according to the authors of the report, which was commissioned by the UK government's Department for Business, Energy & Industrial Strategy (<a href="https://www.gov.uk/government/organisations/department-for-business-energy-and-industrial-strategy" target="_blank">BEIS</a>).</p><p>However, for some industries, such as aviation and agriculture, it will be almost impossible to cut emissions down to zero, says <a href="https://tyndall.ac.uk/people/corinne-le-qu%C3%A9r%C3%A9" target="_blank">professor Corinne Le Quéré</a>, a report author and director of the <a href="https://tyndall.ac.uk/" target="_blank">Tyndall Centre for Climate Change Research</a> at the <a href="https://www.uea.ac.uk/" target="_blank">University of East Anglia</a>.</p><p>In the video below, she explains why the use of NETs could be necessary to counteract the "emissions we don't know how to bring down to zero."</p><p class="shortcode-media shortcode-media-youtube">
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</p><p><strong>Negative Mix<br></strong></p><p>The 133-page report assesses the potential carbon storage of a wide range of proposed NETs, as well as their potential co-benefits and risks.</p><p>This information has been used to create a scenario for the UK in 2050 whereby a suite of NETs are used to reach net-zero emissions.</p><p>The UK currently emits around 450m tonnes of CO2 equivalent (CO2e) a year. Under the <a href="http://www.legislation.gov.uk/ukpga/2008/27/contents" target="_blank">Climate Change Act</a>, the UK is committed to an 80 percent reduction in emissions by the year 2050, relative to 1990 levels.</p><p>However, the Committee on Climate Change (<a href="https://www.theccc.org.uk/" target="_blank">CCC</a>)—the independent body that advises the government on climate policy—has <a href="https://www.carbonbrief.org/ccc-no-need-to-tighten-uks-carbon-budgets-despite-paris" target="_blank">suggested that</a>, if efforts to reduce emissions are increased, the UK could exceed this target. This would lead to annual emissions of 130m tonnes of CO2e by 2050.</p><p>The new scenario assumes that the UK does manage to slash its emissions and that a mix of NETs are used to balance out the remaining 130m tonnes of CO2e in 2050.</p><p>The chart below shows the expected relative contributions of nine techniques. The first five are grouped into "ready to deploy" methods, such as planting forests (pink), restoring habitats such as peatlands and wetlands (purple), enhancing the amount of carbon stored in the soil (blue), building with wood—or "biomass" (green) and using low-carbon concrete for construction (orange).</p><p class="shortcode-media shortcode-media-rebelmouse-image">
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<small class="image-media media-caption" placeholder="add caption...">The potential of various technologies to offset UK emissions (in millions of tonnes of CO2e) in 2050</small><small class="image-media media-photo-credit" placeholder="add photo credit...">Royal Society & Royal Academy of Engineering</small></p><p>The scenario envisages that these "ready to deploy" techniques will be rapidly rolled out across the UK—taking up around 35m tonnes of CO2e, just over a quarter of the UK's total annual emissions, by 2050.<br></p><p>The rapid deployment of these "<a href="https://www.carbonbrief.org/analysis-how-natural-climate-solutions-can-reduce-the-need-for-beccs" target="_blank">natural</a>" techniques would cause considerable land-use change, according to the report.</p><p>For example, the scenario assumes that the UK will plant an additional 1.2m hectares of forest—an area roughly the size of the West Midlands. Many of these forests would be <a href="https://www.carbonbrief.org/planting-a-mix-of-tree-species-could-double-forest-carbon-storage" target="_blank">monocultures</a> made up of species such as willow or poplar, the scientists told the press briefing.</p><p>However, this group of techniques could also come with considerable co-benefits, the scientists added. For instance, increasing the carbon storage potential of the UK's peatlands and wetlands through habitat restoration could boost natural flood defenses and provide more space for native <a href="http://www.ecowatch.com/tag/wildlife">wildlife</a>, the report shows.</p><p><strong>Chemical Cooling</strong></p><p>The second group on the diagram includes two technologies that are "not yet demonstrated at scale." These are "<a href="https://www.carbonbrief.org/guest-post-how-enhanced-weathering-could-slow-climate-change-and-boost-crop-yields" target="_blank">enhanced weathering</a>" (pale green)—a process where silicate rocks are spread over <a href="http://www.ecowatch.com/tag/soil">soils</a> in order to boost the natural process of weathering, which causes CO2 to turn into solid bicarbonate—and the use of "<a href="https://www.carbonbrief.org/negative-emissions-scientists-meet-sweden-first-international-conference" target="_blank">biochar</a>"—a carbon-rich charcoal which, when sprinkled on land, can boost soil carbon storage.</p><p>The scenario suggests that these two techniques could offset 20m tonnes of CO2e (or 15 percent of the UK's total emissions) by 2050—with enhanced weathering accounting for three quarters of this figure.</p><p>To be effective, biochar would need to spread over a quarter of all of the UK's arable land, the report says, while enhanced weathering would need to be undertaken on just under a quarter of all arable land.</p><p>The two techniques would need to be applied separately, the report adds, meaning that, together, the methods would need to be applied to just under half of all of the UK's croplands.</p><p>The report notes that both methods are at a "low-level of technology readiness" and that their contribution to offsetting emissions could grow larger in the second half of the century. For enhanced weathering, around two thirds of the silicate rock needed could be provided by waste materials from the industries including cement and steel, the report adds.</p><p><strong>Capturing Carbon</strong></p><p>The last set of technologies are labelled "requiring CCS [carbon capture and storage]". There are two of these—direct air capture with carbon capture and storage (<a href="https://www.carbonbrief.org/swiss-company-hoping-capture-1-global-co2-emissions-2025" target="_blank">DACC</a>; brown on the diagram) and bioenergy with carbon capture and storage (<a href="https://www.carbonbrief.org/beccs-the-story-of-climate-changes-saviour-technology" target="_blank">BECCS</a>; crimson on the diagram).</p><p>DACC involves using machines to directly "suck" CO2 out of the air and then store it underground. BECCS involves burning crops to create bioenergy, capturing the resulting greenhouse gas emissions in a power plant and storing them underground.</p><p>The scenario assumes that these two technologies will offset 75m tonnes of CO2e—almost 58 percent of the UK's total emissions—by 2050.</p><p>However, the report acknowledges that "neither BECCS nor DACCS have yet been demonstrated to operate at a large scale" and that the development of CCS will be key for the UK to meet its emissions targets. In the report, the authors say:</p><blockquote>"Crucially, meeting the UK target, therefore, depends on rapid development of the carbon transportation and storage infrastructure required for CCS."</blockquote><p>A major barrier to the development of CCS is the <a href="https://www.carbonbrief.org/negative-emissions-scientists-meet-sweden-first-international-conference" target="_blank">cost associated</a> with directly capturing CO2 from the atmosphere.</p><p>The report shows that, if deployed, BECCS could require around 1m hectares of UK land—largely farmland—to be converted into biomass plantations. This could have <a href="https://www.carbonbrief.org/guest-post-how-use-of-land-in-pursuit-of-1-5c-could-impact-biodiversity" target="_blank">consequences for biodiversity and food security</a>, according to the report authors.</p><p><strong>Political Will?</strong></p><p>To reach the scenario outlined in the report, the UK will need to "act quickly" to boost investments in negative emissions research, says <a href="https://www.earth.ox.ac.uk/people/gideon-henderson/" target="_blank">professor Gideon Henderson</a>, chair of the report working group from the <a href="http://www.ox.ac.uk/" target="_blank">University of Oxford</a>. At the sidelines of the press briefing, he told Carbon Brief:</p><p>"The report makes it clear that we would need to act quickly, we would need to ramp up reforestation. In the slightly longer term, we would need to develop technologies that are somewhat unproven, such as biochar. We need research and investigation into those techniques now so we're ready to pursue them in the coming decades. We also need to establish—as soon as we can—CCS infrastructure and scale that up, so that we're ready to store the CO2 that is extracted using future techniques."</p><p>Scaling up NETs would also require changes to UK policy, the researchers say. For example, increasing the price on carbon would be "necessary" to make CO2 removal economically feasible, the report finds.</p><p>In addition, the government will need to introduce more incentives for techniques such as afforestation and enhancing soil carbon stocks.</p><p>On Tuesday (September 11), Conservative MP Simon Clarke handed in a <a href="https://twitter.com/LeoHickman/status/1039786282644398080" target="_blank">letter</a> to the government—backed by 132 MPs and 51 peers—calling for the UK to adopt a net-zero emissions target before 2050.</p><p>In a press statement, Clarke said: </p><blockquote>"To bring our climate back into balance we have to finally end our emissions. We have led the world in confronting this problem and can lead in solving it, drawing on our engineering and scientific prowess that will help bring us to net zero."</blockquote><p class="shortcode-media shortcode-media-twitter_embed">
</p><div id="b96e0" class="rm-shortcode" data-rm-shortcode-id="5LSRKP1576663013"><blockquote class="twitter-tweet twitter-custom-tweet" data-twitter-tweet-id="978645341976211456" data-partner="rebelmouse"><div style="margin:1em 0">Emissions Must Fall By Mid-Century to Meet Paris Temperature Goals, Study Finds https://t.co/pvrOWNHG8V… https://t.co/GtjJE8fkeG</div> — EcoWatch (@EcoWatch)<a href="https://twitter.com/EcoWatch/statuses/978645341976211456">1522162206.0</a></blockquote></div>
<p></p><p><em>Reposted with permission from our media associate <a href="https://www.carbonbrief.org/uk-could-become-net-zero-by-2050-using-negative-emissions" target="_blank">Carbon Brief</a>.</em><br></p>
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BBC headquarters in London. Mike Kemp / In Pictures / Getty Images
After a summer full of extreme weather headlines, The BBC is making a concerted effort to improve its coverage of climate change.
<p>In a "crib sheet" sent to BBC journalists via email last Thursday and obtained by <a href="https://www.carbonbrief.org/exclusive-bbc-issues-internal-guidance-on-how-to-report-climate-change" target="_blank">Carbon Brief</a>, the major news source provided reporters with a climate "editorial policy" and "position" and invited them to attend an hour-long "training course on reporting climate change."</p><p>"After a summer of <a href="http://www.ecowatch.com/tag/heat-wave" target="_self">heatwaves</a>, floods and extreme weather, environment stories have become front of mind for our audiences. There are a number of important related news events in the coming months—including the latest report from the <a href="http://www.ipcc.ch/" target="_blank">UN Intergovernmental Panel on Climate Change</a> and <a href="https://www.gov.uk/government/news/landmark-week-of-action-to-celebrate-clean-growth" target="_blank">Green Great Britain Week</a> in October—so there will be many more stories to cover. Younger audiences, in particular, have told us they'd like to see more journalism on the issue," the email, written and sent by BBC Director of News and Current Affairs Fran Unsworth, began. </p><p>The course and new policy and position document, which Carbon Brief said were the first formal climate reporting guidelines in BBC history, came after the BBC apologized last year for breaking its editorial guidelines for "not sufficiently challenging" former Conservative chancellor and <a href="http://www.ecowatch.com/tag/climate-denier" target="_self">climate denier</a> Lord Nigel Lawson in an interview on Radio 4's Today program in 2017. </p><p>The BBC was also censured by regulator <a href="https://www.ofcom.org.uk/" target="_blank">Ofcom</a> for the interview, in which it failed to challenge Lawson's claim that temperatures had not risen in the past decade, <a href="https://www.theguardian.com/environment/2018/sep/07/bbc-we-get-climate-change-coverage-wrong-too-often" target="_blank">The Guardian reported</a>. </p><p>Another interview with Lawson in 2014 saw the Today program censured by the BBC complaints unit.</p><p>The new editorial policy began by addressing past mistakes. </p><p>"Climate change has been a difficult subject for the BBC, and we get coverage of it wrong too often," the document obtained by Carbon Brief said.</p><p>The BBC climate position also warned journalists to "be aware of false balance."</p><p>'To achieve impartiality, you do not need to include outright deniers of climate change in BBC coverage, in the same way you would not have someone denying that Manchester United won 2-0 last Saturday. The referee has spoken," The BBC said. </p><p>The policy document went on to state that it was sometimes appropriate to include skeptical voices when talking about the pace of climate change or debating policy responses, but that a speakers' affiliations and scientific expertise should be stated to the audience. </p><p>"This set of BBC guidelines is long overdue. There have been too many occasions when the BBC's audience has been misled over the realities of climate change," University of Reading climate science Prof. Ed Hawkins told Carbon Brief, though he thought the policy could have been clearer in its definition of "false balance." </p><p>Hawkins clarified that the IPCC report was not being updated this year, but rather that the body was publishing a <a href="http://www.ipcc.ch/news_and_events/ma-p48.shtml" target="_blank">special report</a> on the impacts of 1.5 degrees Celsius of warming. </p><p>Former BBC environment correspondent and current <a href="https://eciu.net/" target="_blank">Energy and Climate Intelligence Unit</a> Director Richard Black also welcomed the news. </p><p>"The course will be criticised by some—words like 'stifling the debate'—but those voices are decreasingly important in the country. I think the real takeaway from this is that the BBC has decided it no longer cares about evidence-free allegations of 'bias'. It's to be commended for putting its mojo on display," he told The Guardian. </p>
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Roots of mangrove trees, Para State, Brazil. Ricardo Lima / Getty Images
By Daisy Dunne
The vast mangroves of the Amazon store twice as much carbon per hectare as the region's tropical forests, new research shows.
The relatively understudied ecosystem also stores 10 times more carbon than Amazon savannahs—a type of grassy plain with sparsely populated trees, according to the study.
<p>However, the wetlands face threats from <a href="https://www.ecowatch.com/tag/deforestation">deforestation</a> and <a href="https://www.ecowatch.com/tag/climate-change">climate change</a>, the researchers say. Introducing more measures to protect mangroves will be key to preserving its large carbon store, they add.</p><p>The findings provide "yet more evidence of the extraordinary carbon stocks found in mangroves" worldwide, another scientist told Carbon Brief.</p><p><strong>Wild Wetlands</strong></p><p>The Amazon is well known for its 167m hectares of rainforest, but is less known for being home to close to 1m hectares of "<a href="https://www.carbonbrief.org/mangrove-deforestation-emits-as-much-co2-as-myanmar-each-year" target="_blank">mangrove</a>" forests.</p><p>Mangroves are trees and shrubs that grow in coastal waters across the tropics and subtropics. They are most easily recognized by their tall protruding roots, which they use to anchor themselves against incoming tides.<br></p><p>The new study, published in <a href="http://rsbl.royalsocietypublishing.org/lookup/doi/10.1098/rsbl.2018.0208" target="_blank">Biology Letters</a>, is the first to make an on-the-ground estimate of how much carbon is stored in the Amazon's vast wetlands.</p><p>It finds that, on average, Amazon mangroves store 511 tonnes of carbon per hectare—roughly double that of the region's rainforests. Writing in their research paper, the authors said:</p><blockquote>"The carbon stocks of the Amazon mangroves were over twice those of upland evergreen forests [rainforests] and almost 10-fold those of tropical dry forest [savannahs]."</blockquote><p><strong>Calculating Carbon</strong></p><p>For the study, the researchers visited nine mangroves—along with three <a href="https://oceanservice.noaa.gov/facts/saltmarsh.html" target="_blank">salt marshes</a> (a type of coastal grassland)—within the Brazilian Amazon.</p><p>At each site, they took measurements of the amount of carbon stored "aboveground," in the trees and fallen leaf litter, and "belowground," in the roots and soil.</p><p>To measure carbon stocks, the researchers measured changes to "biomass"—the weight amassed from the production of new leaves and shoots, or the thickening of a tree trunk, for example.</p><p>Plants take in CO2 from the atmosphere during photosynthesis and later use it to build and extend their trunks, stems and roots. Because of this, measuring changes to biomass gives scientists an idea of how much carbon is being stored in a given area over time.</p><p>The researchers then compared their estimates to previous data on carbon storage in the Amazon rainforest.</p><p>The chart below shows the average amount of carbon stored in tonnes per hectare by Amazon mangroves (far left) and Amazon rainforests (second left). The charts also include results from the salt marshes (second right) and data taken from a <a href="https://www.cambridge.org/core/journals/journal-of-tropical-ecology/article/ecosystem-structure-in-the-brazilian-cerrado-a-vegetation-gradient-of-aboveground-biomass-root-mass-and-consumption-by-fire/3D4953C7ECBD87E874F930632CEE8B5E" target="_blank">previous study</a> by the researchers undertaken in desert-like "<a href="https://www.worldwildlife.org/ecoregions/nt1304" target="_blank">Caatinga</a>" and savannah-like "<a href="http://wwf.panda.org/knowledge_hub/where_we_work/cerrado/" target="_blank">Cerrado</a>" ecosystems.</p><p>On the chart, green shows the results for aboveground carbon, brown shows the results for shallow belowground carbon and black shows the result for deep belowground carbon. (Rainforest soil tends to be shallow and nutrient-poor, while deep deposits of soil can build up in mangrove forests.)</p><p class="shortcode-media shortcode-media-rebelmouse-image">
<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xODQ3ODI4OC9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTYxMDc2MjEwNH0.aSawkPVYnFEVaxhxVpJB2RjVZcICAP2pAs7dj_3wcNQ/img.png?width=980" id="32e3b" class="rm-shortcode" data-rm-shortcode-id="37a9d01fbab3389979e901c34c3b2851" data-rm-shortcode-name="rebelmouse-image">
<small class="image-media media-caption" placeholder="Add Photo Caption...">Estimated carbon stock in tonnes per hectare in Amazon mangroves and forests, "Caatinga" (desert-like) mangroves and forests, salt marshes and "Cerrado" (savannah) ecosystems</small><small class="image-media media-photo-credit" placeholder="add photo credit...">Boone Kaufmann et al. (2018)</small></p><p>The results show that, on average, Amazon mangroves store around twice as much carbon per hectare as Amazon forests.<br></p><p>The majority of the carbon stored by mangroves is held in the soil, the research shows. Wetland soils tend to be carbon-rich because they are waterlogged, which slows the rate at which plant matter decomposes.</p><p>When decomposition is slow, carbon-rich materials are able to build up, explained <a href="https://www.zoo.cam.ac.uk/directory/dr-mark-spalding" target="_blank">Dr. Mark Spalding</a>, a marine scientist and honorary fellow at the <a href="https://www.cam.ac.uk/" target="_blank">University of Cambridge</a>, who was not involved in the study. He told Carbon Brief:</p><blockquote>"The soils are very carbon rich. This is because they are permanently waterlogged and, so, carbon doesn't break down. <a href="https://www.carbonbrief.org/guest-post-a-plan-to-solve-mysteries-of-congos-vast-tropical-peatland" target="_blank">Freshwater peats</a> have similar soil carbon concentrations."</blockquote><p>The tightly-packed nature of mangrove trees also enhances carbon storage in comparison to <a href="https://www.ecowatch.com/tag/forests">forests</a>, which tend to be more sparse, he added.</p><p><strong>Looming Threats</strong></p><p>The results suggest that protecting the Amazon wetlands could play a larger role in slowing climate change than previously thought, the authors say.</p><p>Amazon wetlands are currently threatened by deforestation—often to make way for fish farming—as well as <a href="https://www.wwt.org.uk/conservation/saving-wetlands/countering-wetland-threats/climate-change/" target="_blank">rising temperatures</a>, which could cause wetlands to dry out by increasing rates of evaporation. In their research paper, the authors said:</p><blockquote>"The vast extent of Brazilian mangroves coupled with the large quantities of greenhouse gas emissions that results from deforestation underscores their potential value in climate change mitigation."</blockquote><p>The findings provide evidence of the "extraordinary carbon stocks found in mangroves," Spalding said, but a key question remains about how stable this carbon is:</p><blockquote>"Whether this carbon is short-lived or whether a significant proportion is being buried for the long-term in offshore sediments is a very important research question."</blockquote><p class="shortcode-media shortcode-media-twitter_embed">
</p><div id="62921" class="rm-shortcode" data-rm-shortcode-id="F9GCTB1576662161"><blockquote class="twitter-tweet twitter-custom-tweet" data-twitter-tweet-id="1012086943168061441" data-partner="rebelmouse"><div style="margin:1em 0">Tropical Forests Lost 40 Football Fields of Tree Cover Per Minute in 2017 https://t.co/Xp1B25yonb @EARTHWORKS @GreenpeaceAustP</div> — EcoWatch (@EcoWatch)<a href="https://twitter.com/EcoWatch/statuses/1012086943168061441">1530135305.0</a></blockquote></div>
<p></p><p><em>Reposted with permission from our media associate <a href="https://www.carbonbrief.org/amazon-mangroves-twice-as-carbon-rich-as-its-rainforests" target="_blank">Carbon Brief</a>.</em><br></p>
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David Cornwell / Flickr / Cc By-Nc-Nd 2.0
By Daisy Dunne
Global warming could increase both the number and appetite of insect pests, new research finds, which could pose a serious threat to global crop production.
<p>The study finds that global warming of 2C above pre-industrial levels—which is the limit set by the <a href="https://www.carbonbrief.org/interactive-the-paris-agreement-on-climate-change" target="_blank">Paris agreement</a>—could cause pest-related yield losses from wheat, rice and maize to increase by 46 percent, 19 percent and 31 percent, respectively.</p><p>And each additional degree of temperature rise could cause yield losses from insect pests to increase by a further 10-25 percent, the research shows.</p><p>Losses from pest infestation are likely to be largest in China, the U.S. and France—three of the world's most important grain producers, according to the findings.</p><h4>Soaring Swarms</h4><p>At present, around <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-3059.2010.02411.x" target="_blank">10-16 percent</a> of global crop production is lost to pests—including insects, fungi and bacteria.</p><p>Thousands of insect species are known to threaten food production. One of the most well-known pests, the desert locust, feeds on a wide range of crops—including rice, maize and sugarcane—and can swarm and strip a crop field <a href="https://www.bbc.co.uk/news/science-environment-15623490" target="_blank">within an hour</a>.</p><p>Other insects, such as the western corn rootworm, target specific crops. The rootworm, for example, feeds on maize during both its larval and adult beetle life stages and currently costs U.S. farmers around <a href="https://pubag.nal.usda.gov/pubag/downloadPDF.xhtml?id=37279&content=PDF" target="_blank">$1bn a year</a> in lost revenue.</p><p>The new study, published in <a href="http://science.sciencemag.org/cgi/doi/10.1126/science.aat3466" target="_blank">Science</a>, explores how climate change could alter the activity of 38 of the world's most-studied insect crop pests.</p><p>Climate change could increase the activity of insect pests in two ways, according to the research team, which was led by <a href="https://environment.uw.edu/faculty/curtis-deutsch/" target="_blank">Prof. Curtis Deutsch</a>, an ecologist from the <a href="http://www.washington.edu/" target="_blank">University of Washington</a>.</p><p>First, rising temperatures boost the rate at which insects can digest food—causing them to demolish crops at a faster rate.</p><p>Second, in temperate regions, warming temperatures could cause insects—which are <a href="http://rspb.royalsocietypublishing.org/content/royprsb/284/1849/20162328.full.pdf" target="_blank">ectothermic</a> or "cold-blooded"—to become more active and, thus, more able to reproduce.</p><h4>Crop Countdown</h4><p>For the study, the researchers made of use of existing data on how temperature is known to affect the population growth rate, food consumption rate and overall survival of insect pests under laboratory conditions.</p><p>The researchers used this information to inform a set of models projecting yield losses from insect pests for wheat, rice and maize under different levels of temperature rise. The projections assumed that total global crop yields will remain the same as today.</p><p>The charts below show the expected crop yield loss in megatonnes per year as a result of increased insect food consumption—or "metabolic activity"—(purple triangles) and population growth (orange circles and green asterisks) for wheat (A), rice (B) and maize (C) under various levels of global temperature rise. A dashed line is used to indicate the current loss as a result of insect pests.</p>
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<p><em>[Chart above] — Projected crop yield losses (megatonnes per year) as a result of increased insect metabolic activity (purple triangles) and two estimations of population growth using different demographic parameters (orange circles and green asterisks) for wheat (A), rice (B) and maize (C) under temperature rise of 1-5C above pre-industrial levels. A dashed line shows the current amount of crop losses from insect pests. Source: Deutsch et al. (2018)</em></p><p><span></span>The results show that, under 2C of global warming, pest-related yield losses from wheat, rice and maize increase by 46 percent, 19 percent and 31 percent, respectively, when compared to current levels of loss. Each additional degree of temperature rise could cause global yield losses from insect pests to increase by a further 10-25 percent, the results suggest.<br></p><p>Losses are projected to be largest for maize and wheat because these crops are mostly grown in temperate regions – where warming is expected to boost insect population numbers, the researchers say.</p><p>Rice, on the other hand, is grown mostly in tropical regions—where temperatures are already optimal for insect reproduction. Further temperature increases are therefore likely to cause small declines in insect numbers, the research finds, leading to an overall smaller effect on yield losses.</p><p>The maps below show the projected geographic pattern of insect-related yield losses for wheat (A), rice (B) and maize (C) under 2C of global warming. On the maps, dark red shows large percentage increases in crop losses while dark blue shows large decreases.</p>
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<p><em>[Map above] — The projected distribution of insect-related yield losses for wheat (A), rice (B) and maize (C) under 2C of global warming. Dark red shows increased losses, while dark blue shows decreased losses. Source: Deutsch et al. (2018)</em></p><p>The maps show how the largest losses to crop yields in percentage terms are expected in Europe and North America, including in the U.S. and France—two of the world's largest grain producers.<br></p><p>Europe's wheat-growing regions—collectively the most productive in the world—could be particularly affected by losses, the results show. Up to 11 European countries, including the UK, Sweden and Ireland, could face insect-related losses of 75 percent or higher, the study finds.</p><p>Moderate losses are also projected across much of sub-Saharan Africa and southeast Asia—two regions currently facing high levels of hunger. Writing in their research paper, the authors said:</p><blockquote>"Poor grain consumers and farming households, who account for a large share of the world's 800 million people living in chronic hunger, will suffer most."<br></blockquote><h4>Knowing the Enemy</h4><p>The findings should serve a "call for action on climate change mitigation and adaptation," <a href="https://www.westernsydney.edu.au/hie/people/researchers/associate_professor_markus_riegler" target="_blank">Prof. Markus Riegler</a>, an insect biologist from <a href="https://www.westernsydney.edu.au/" target="_blank">Western Sydney University</a>, writes in an <a href="http://science.sciencemag.org/cgi/doi/10.1126/science.aau7311" target="_blank">accompanying perspectives article</a>. He said:</p><blockquote>"Everyone must be involved in change: farmers, industries, policymakers, and the wider society. There is also an increased need to focus on plant protection, particularly given that many insecticides are being banned over human and environmental health concerns."<br></blockquote><p>The research offers "a global perspective" of how climate change could impact the damages caused by pests, said <a href="https://www.slu.se/en/cv/christer-bjorkman/" target="_blank">Prof. Christer Björkman</a>, an insect ecologist from the <a href="https://www.slu.se/en/" target="_blank">Swedish University of Agricultural Sciences</a>, who was not involved in the study. However, the study does have a few shortcomings, he told Carbon Brief:</p><blockquote>"One is that the authors only model the pests themselves. This is a great simplification because we know their host plants and their natural enemies are affected by the same temperature changes."<br></blockquote><p>Research shows that climate change could impact many of these enemies – including <a href="https://www.carbonbrief.org/double-threat-to-uks-birds-and-butterflies-from-climate-change-and-land-use" target="_blank">birds</a>, <a href="https://www.carbonbrief.org/climate-change-to-become-greatest-pressure-on-biodiversity-by-2070" target="_blank">mammals</a> and <a href="https://www.carbonbrief.org/climate-change-drive-third-parasites-extinction-2070" target="_blank">parasites</a>. Björkman said:</p><blockquote>"In other words, the study ignores many key ecological interactions of potentially great importance. Another [unconsidered factor is] the nutritional value of plants may change."<br></blockquote><p>Research covered by <a href="https://www.carbonbrief.org/rising-co2-levels-could-push-hundreds-of-millions-into-malnutrition-by-2050" target="_blank">Carbon Brief</a> earlier this week found that the nutritional value of key crops including rice, wheat and maize is likely to fall as CO2 levels rise.</p><p>If crops become less nutritious, insects will have to consume more plant matter to get the nutrients they need, Björkman said, potentially raising yield losses further.</p><p> <em>Reposted with permission from our media associate <a href="https://www.carbonbrief.org/rise-in-insect-pests-under-climate-change-to-hit-crop-yields-study-says" target="_blank">Carbon Brief</a>.</em><em></em></p>
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Cars drive down a hill in a mandatory evacuation area as the Holy Fire burns in Cleveland National Forest on Aug. 8 in Lake Elsinore, California. The fire has burned at least 6,200 acres and destroyed twelve structures. Mario Tama / Getty Images
By Daisy Dunne
Sharp declines in summer rainfall could be a "primary driver" of the record-breaking wildfires ripping across the western U.S., research shows.
Using satellite data, the study finds that there have been "previously unnoted" declines in summer rainfall across close to a third of forests in the western U.S. over the past four decades. These declines are "strongly correlated" with wildfire increases, the study finds.
<p>It is likely that <a href="https://www.ecowatch.com/tag/climate-change">climate change</a> has played a role in the diminishing rains, the lead author told <a href="https://www.carbonbrief.org" target="_blank">Carbon Brief</a>. However, it is still not clear to what extent global warming—over natural climate variability—is to blame.</p><p>The findings suggest that the role of declining rainfall in worsening wildfires has been previously "overlooked" in comparison to other major drivers such as rising temperatures, the author adds.</p><p><strong>Sea of Flames</strong></p><p>California is currently facing its <a href="https://www.nytimes.com/interactive/2018/08/10/us/california-fires.html" target="_blank">largest wildfires on record</a>. Across the state, more than 332,000 hectares (820,000 acres) of forest have already been scorched—more than twice the area burnt during the same time last year.</p><p>Out of the 15 largest wildfires ever recorded in California, <a href="https://www.nytimes.com/interactive/2018/08/10/us/california-fires.html" target="_blank">10</a> have occured since 2000. Across the western U.S., forest fires have become fives times more frequent and six times larger, on average, since the 1970s, <a href="http://rstb.royalsocietypublishing.org/content/371/1696/20150178" target="_blank">research</a> shows.</p><p>As <a href="https://www.carbonbrief.org/factcheck-how-global-warming-has-increased-us-wildfires" target="_blank">Carbon Brief</a> recently explained in a detailed fact check, the chances of a wildfire spreading and becoming large are affected by myriad factors. However, <a href="http://science.sciencemag.org/content/313/5789/940" target="_blank">research</a> shows that there is a correlation between rising spring and summer temperatures and the amount of land burned by forest fires in the western U.S. in recent decades.</p><p>When temperatures are warmer, rates of evaporation increase—meaning more moisture is drawn out from the land, leaving it dry. A parched land surface creates <a href="https://www.carbonbrief.org/carbon-emissions-from-amazon-wildfires-could-counteract-deforestation" target="_blank">tinderbox conditions</a>—allowing wildfires to spread more quickly.</p><p>The new research, published in the <a href="http://www.pnas.org/cgi/doi/10.1073/pnas.1802316115" target="_blank">Proceedings of the National Academy of Sciences</a>, pinpoints a second important driver of wildfires—recent declines in summer rainfall.</p><p>The findings suggest that such declines could be the main cause of increases in the severity of the wildfire season in recent years, said lead author <a href="http://hs.umt.edu/geography/people/default.php?s=Holden" target="_blank">Dr. Zachary Holden</a>, an ecologist from the <a href="https://www.fs.fed.us/" target="_blank">U.S. Forest Service</a> in Missoula, Montana. He told Carbon Brief:</p><blockquote>"We found that across large areas of the west, there have been significant declines in precipitation during the western fire season. We also found that the length of dry windows—consecutive days without any rain—are becoming longer."</blockquote><p>Declines in rainfall could be affecting the severity of wildfires in two main ways, he said.</p><p>First, less rainfall leads to the drying out of vegetation—which can then act as tinder for a spreading fire. Second, long spells without rain cause more sunlight to be converted to heat at the earth's surface—leading to further drying at the land's surface. Holden said:</p><blockquote>"Overall, we found that reduced precipitation has had a larger impact on historical trends in western wildfire activity than the effects of winter snowpack or air temperatures."</blockquote><p><strong>Drying Up</strong></p><p>For the study, the researchers compared temperature and rainfall data taken from weather stations across the western U.S. to forest fire data captured by satellites. The charts below show forest cover (left) and forest wildfire area burnt per year from 1984 to 2015 (right) in the western U.S.</p><p class="shortcode-media shortcode-media-rebelmouse-image">
<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xODMyOTQ3NS9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTYxMjEzMTIzMn0.2Ys4XjxXAlwf5qJJGvasFOUFWjDZiaQXVS-lsk98yhM/img.png?width=980" id="3efaa" class="rm-shortcode" data-rm-shortcode-id="6d921fdcb9bfb7e9b18dc75f5244281c" data-rm-shortcode-name="rebelmouse-image">
<small class="image-media media-caption" placeholder="add caption...">Forest cover and forest wildfire area burnt per year from 1984 to 2015 in eight western U.S. domains</small><small class="image-media media-photo-credit" placeholder="add photo credit...">Holden et al. (2018)</small></p><p>The researchers used this information to explore three hypotheses. The first was that increases in forest fires have primarily been driven by decreases in <a href="https://www.carbonbrief.org/declining-snowpack-could-threaten-1-9bn-people-with-water-shortages" target="_blank">mountain snowpack</a>.<br></p><p><a href="https://www.nature.com/articles/s41612-018-0012-1" target="_blank">Research</a> suggests that snowpack levels in California's key mountain ranges—including the Sierra Nevada and the Rocky Mountains—are declining year on year.</p><p>During the spring and summer, meltwater from accumulated mountain snow provides a key source of <a href="http://www.ecowatch.com/tag/water">water</a> across the state. Because of this, some have <a href="http://www.pnas.org/content/109/9/E535" target="_blank">suggested</a> that declines in snowpack could be the key driver of the dry conditions that aid the spread of wildfires.</p><p>However, the researchers found that declines in snow meltwater were not significantly correlated with the annual area burned by wildfires in the western U.S. over the study period.</p><p>The second hypothesis was that forest fire increases have been driven by rising temperatures, while the third was that increases had been driven by declining rainfall.</p><p>Similar to <a href="http://science.sciencemag.org/content/313/5789/940" target="_blank">previous studies</a>, the researchers did find a strong correlation between temperature increases and wildfire temperatures across the regions studied.</p><p>However, in contrast to the earlier research, the researchers also found an even stronger correlation between declines in summer rainfall and increases in forest fires. They considered "summer" to be from May to September.</p><p>They found that 82 to 94 percent of forest land in the western U.S. experienced summer rainfall declines from 1979 to 2016. The declines in rainfall were statistically significant in 31 to 35 percent of forests.</p><p>The average forest experienced summer rain declines of 4 percent (5mm) per decade, while the worst affected areas experienced declines of 47 percent (77mm), the research shows.</p><p><strong>Rainy Days</strong></p><p>The researchers also looked at changes in the number of summer "wetting rain days"—days when rainfall exceeded 2.5mm.</p><p>They found, on average, forests experienced one less wetting rain day per decade, while the worst affected forests experienced six fewer days per decade</p><p>In addition, the researchers found that the average length of dry spells increased in many parts of the western U.S. from one decade to the next.</p><p>The maps below show changes to summer rainfall (left), number of rain days (middle) and the average length of time without rain (right) in the western U.S.</p><p>The top and middle columns show the results from the two different datasets called "GRIDMET" and "DAYMET," while the bottom column shows the results from individual weather stations (shown as dots). For the first two columns, red shows decreases while green shows increases. For the last column, green shows decreases while red shows increases.</p><p class="shortcode-media shortcode-media-rebelmouse-image">
<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xODMyOTU0OS9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTYxNTQ1NTY0MX0.Uhp65c6hJvOjO1L13dz29NwkjKDux14enGmbv4vT7jg/img.png?width=980" id="00b49" class="rm-shortcode" data-rm-shortcode-id="0ca673ca2a8a7099d3324a1e199998f4" data-rm-shortcode-name="rebelmouse-image">
<small class="image-media media-caption" placeholder="add caption...">Decadal changes to summer rainfall (left), number of "wetting rain days" (middle) and the average length of time without rain (right) for the GRIDMET (top) and DAYMET (middle) datasets, as well as individual weather stations (bottom; marked with dot)</small><small class="image-media media-photo-credit" placeholder="add photo credit...">Holden et al. (2018)</small></p><p>The maps show how regions that have seen the largest wildfire increases, such as the Pacific Northwest and the Northern Rockies, have also experienced declines in summer rainfall and increases in the average length of dry spells over the past four decades.<br></p><p>The chart below show the relationship between the number of wetting days (x axis) and the area of land burned by wildfires from 1984 to 2015 (y axis).</p><p class="shortcode-media shortcode-media-rebelmouse-image">
<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xODMyOTU2Ni9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTY0ODAwNjgxOX0.50rB4X5nVZKiU8ZGFL7gR9-n6H-gmpMR4cemQmd-46s/img.png?width=980" id="c41f8" class="rm-shortcode" data-rm-shortcode-id="ee78a4c62d18ac6e52054861153342e2" data-rm-shortcode-name="rebelmouse-image">
<small class="image-media media-caption" placeholder="add caption...">The relationship between the number of "wetting rain days" and area burned by wildfires in the western U.S. from 1984 to 2015</small><small class="image-media media-photo-credit" placeholder="add photo credit...">Holden et al. (2018)</small></p><p>The chart shows that there is strong correlation between the observed decline in rainy days and the amount of land burned by wildfires, Holden said:<br></p><blockquote>"We don't know whether long rain-free periods in the west are likely to continue, or increase. Here in western Montana, we've just broken the historical record for the longest continuous number of days with no rain. If we see continued summer drying, we expect fire seasons to be as or more severe in the future."</blockquote><p><strong>Link to Sea Ice?</strong></p><p>The study did not aim to separate out the extent to which climate change and natural climate variability are behind the observed summer rainfall declines, Holden said.</p><p>However, <a href="https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2012GL051000" target="_blank">recent research</a> suggests that the <a href="https://www.carbonbrief.org/guest-post-predictable-first-ice-free-arctic-summer" target="_blank">decline in Arctic sea ice extent</a>—in part, <a href="https://www.carbonbrief.org/humans-causing-up-to-two-thirds-arctic-summer-sea-ice-loss-study-confirms" target="_blank">caused by climate change</a>—could be contributing to longer summer dry periods, he said.</p><p>This is because declines in Arctic <a href="http://www.ecowatch.com/tag/sea-ice">sea ice</a> extent could be causing the winds that carry weather systems into the western U.S. to weaken. The slowing of winds allows patterns of weather—such as a dry spell—to persist for longer over one area, Holden said:</p><blockquote>"It's likely a combination of both climate change—through sea ice changes—and natural variability—through ocean temperature variations—and further study is needed to better describe the drivers of these changes."</blockquote><p>The research "adds evidence" to what is known about how climatic factors influence the severity of wildfires in the western U.S., said <a href="https://www.uidaho.edu/sci/geography/people/faculty/jabatzoglou" target="_blank">professor John Abatzoglou</a>, a wildfire researcher from the <a href="https://www.uidaho.edu/" target="_blank">University of Idaho</a>, who was not involved in the study. He told Carbon Brief:</p><blockquote>"Precipitation during the fire season is certainly an important factor as it helps raise fuel moisture and can aid in suppression efforts on active fires. The effect to which anthropogenic climate change is behind declines in summer precipitation in the west is unknown."</blockquote><p>However, the researchers may have overestimated the relative importance of rainfall in comparison to other drivers, such as "atmospheric aridity"—the general dryness of the air, said <a href="https://www.ldeo.columbia.edu/user/williams" target="_blank">professor Park Williams</a>, a researcher in climate and ecology from <a href="https://www.columbia.edu/" target="_blank">Columbia University</a>, who was also not involved in the study. He told Carbon Brief:</p><blockquote>"The authors' method seems to assume that all of the co-variability shared between precipitation and atmospheric aridity is due to precipitation. This undoubtedly leads to precipitation taking a little more credit than it should for year-to-year variations in burned area, and to atmospheric aridity consequently taking less than it should."</blockquote><p class="shortcode-media shortcode-media-twitter_embed">
</p><div id="14a52" class="rm-shortcode" data-rm-shortcode-id="KSBZKO1576662909"><blockquote class="twitter-tweet twitter-custom-tweet" data-twitter-tweet-id="1025700166907711493" data-partner="rebelmouse"><div style="margin:1em 0">'New World Record': #Imperial, #California Felt #Rain at 119°F #heatwave https://t.co/CMl91eHDgF</div> — EcoWatch (@EcoWatch)<a href="https://twitter.com/EcoWatch/statuses/1025700166907711493">1533380951.0</a></blockquote></div>
<p></p><p><em>Reposted with permission from our media associate <a href="https://www.carbonbrief.org/summer-rainfall-declines-primary-driver-of-surge-in-us-wildfires" target="_blank">Carbon Brief</a>.</em><br></p>
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Scattered rainfall over dry season fields before harvest in the Sahel near Bahn Yatenga Burkina Faso Africa. The region is regularly affected by droughts. Getty Images
By Daisy Dunne
Releasing aerosols into the atmosphere in order to limit the rise in global temperature would not stave off damage to crop yields, a new study suggests.
Scientists have suggested that intentionally releasing aerosols into the atmosphere—a type of "solar geoengineering"—could help to limit global warming by reflecting away incoming sunlight in a similar way to a volcanic eruption.
<p>The new research uses historical data to investigate how past major volcanic eruptions have impacted global crop yields. It finds that, following past eruptions, global crop yields have been negatively impacted by a reduction in direct sunlight—which impairs the ability of plants to photosynthesize.</p><p>The findings suggest that, if ever used, solar geoengineering could benefit crops by cooling temperatures and reducing the risk of heat stress. However, this positive effect could be largely offset by the negative impacts associated with a reduction in sunlight, the authors say.</p><p>However, the new research is "limited" and does not take into account the differences that are likely to exist between volcanic eruptions and solar geoengineering, other scientists tell <a href="https://www.carbonbrief.org/" target="_blank">Carbon Brief</a>. Therefore, they say, it should not be used to draw "solid conclusions."</p><p><strong>Artificial Volcanoes</strong></p><p><a href="https://www.carbonbrief.org/explainer-six-ideas-to-limit-global-warming-with-solar-geoengineering" target="_blank">Solar geoengineering</a> is a term used to describe a set of still-hypothetical technologies that could limit global warming by reflecting more sunlight away from Earth.</p><p>The most commonly proposed technology is "<a href="https://www.carbonbrief.org/explainer-six-ideas-to-limit-global-warming-with-solar-geoengineering" target="_blank">stratospheric aerosol injection</a>," a technique where reflective solid particles known as aerosols—such as sulphur dioxide—would be released high up in the stratosphere using, for example, a high-altitude balloon or plane.</p><p>Because the technique has never been tested, it is still unclear what its impacts would be.</p><p>However, <a href="http://rsta.royalsocietypublishing.org/content/376/2119/20160454" target="_blank">previous research</a> using modeling suggests that releasing aerosols could limit temperature rise and restore rainfall to pre-industrial conditions. This could benefit crop production, which is likely to face threats from <a href="https://www.carbonbrief.org/climate-change-threatens-staple-crops-in-africa-study-says" target="_blank">heat stress and drought</a> as the <a href="http://www.ecowatch.com/tag/climate-change">climate warms</a>.</p><p>Yet, other scientists have <a href="https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2016GL071209" target="_blank">postulated</a> that solar geoengineering could be harmful to crops. This is because the presence of reflective aerosols reduces the amount of direct sunlight reaching plants. Plants absorb sunlight and use it to create energy during photosynthesis.</p><p>The new research, published in <a href="https://www.nature.com/articles/s41586-018-0417-3" target="_blank">Nature</a>, is the first to look at the potential impacts of solar geoengineering via the use of "real world" analogues—two previous volcanic eruptions.</p><p>When a volcano erupts, it spews out ash, dust, CO2 and sulphur dioxide high into the atmosphere. The sulphur dioxide combines with water to form <a href="https://www.scientificamerican.com/article/how-do-volcanoes-affect-w/" target="_blank">sulfuric acid aerosols</a>, which—along with the ash and dust—temporarily cool the planet by reflecting away sunlight.</p><p>The two eruptions include Mexico's El Chichón in 1982 and Mount Pinatubo in the Philippines in 1991—the latter of which, in its aftermath, released enough aerosols to cause <a href="https://www.carbonbrief.org/analysis-how-could-agung-volcano-bali-affect-global-temperature" target="_blank">average global temperatures to dip by 0.5°C</a>, according to the researchers.</p><p class="shortcode-media shortcode-media-rebelmouse-image">
<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xODI3MzE1MS9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYxODgyODk5NX0.Pa_ZoRSJiGo0EfJ7eoTf2QWPFOag-MYYd67qtjk_Nok/img.jpg?width=980" id="c8902" class="rm-shortcode" data-rm-shortcode-id="37b576db72ad7655ae633568b485e0aa" data-rm-shortcode-name="rebelmouse-image">
<small class="image-media media-caption" placeholder="add caption...">Mount Pinatubo eruption, June 12, 1991, Luzon, Philippines</small><small class="image-media media-photo-credit" placeholder="add photo credit...">Dave Harlow, USGS / Wikimedia Commons</small></p><p>The findings of the research suggest that, if solar geoengineering were to be used, its impact on incoming sunlight would "wash out" any potential benefits the technology would have for <a href="http://www.ecowatch.com/tag/agriculture">agriculture</a>, lead author <a href="http://www.globalpolicy.science/jonathan-proctor/" target="_blank">Jonathan Proctor</a>, a Ph.D. student at the <a href="http://www.globalpolicy.science/" target="_blank">Global Policy Laboratory</a> at the <a href="https://www.berkeley.edu/" target="_blank">University of California, Berkeley</a>, told a press briefing. He said:<br></p><p>"The implications of this are that solar geoengineering, using sulphate-based aerosols like we saw emitted from these volcanic eruptions, may be an ineffective way to mitigate the damages that climate change poses to global agricultural production."</p><p><strong>Yielding Results</strong></p><p>For the study, the researchers used historical data taken from the United Nations Food and Agricultural Organization (<a href="http://www.fao.org/home/en/" target="_blank">FAO</a>) to explore how the yields of several crops, including wheat, maize and rice, were affected in the aftermath of each eruption.</p><p>The chart below shows changes to several variables, including aerosol cover, average global temperature and average global crop yields between 1980 and 2010. On the chart, the dashed lines show when the eruptions of El Chichón and Mount Pinatubo occurred.</p><p class="shortcode-media shortcode-media-rebelmouse-image">
<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xODI3MzE1Ni9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTY0NjQ5MjcyNX0.xsWkjfYCv0yK_NdWZtZ9Xk8uVhWSW-l99H9J_jfkNLU/img.png?width=980" id="cf695" class="rm-shortcode" data-rm-shortcode-id="14495730d8fb681fd02b69f8b21be016" data-rm-shortcode-name="rebelmouse-image">
</p><p class="caption">Chart shows: (a) the average aerosol cover; (b) average temperature change caused by the natural climatic event <a href="https://www.carbonbrief.org/interactive-much-el-nino-affect-global-temperature" target="_blank">El Niño</a>; (c) global average temperature change; (d) global average rainfall change; (e) global average cloud cover; and (f) the change in global average crop yield for maize (orange), wheat (grey), soy (blue) and rice (green), from 1980-2010. The dashed lines show when the eruptions of El Chichón and Mount Pinatubo occured. Source: Proctor et al. (2018). The charts show how, around the time of each volcanic eruptions, global crop yields tend to decline abruptly.<br></p><p>The researchers estimate that the impact of the Mount Pinatubo eruption on sunlight caused global yields of maize to fall by 9 percent and global yields of wheat, soy and rice to fall by an average of 5 percent.</p><p>The El Chichón eruption had a "significant" impact on maize yields, but only a small effect on yields of other crops, the research shows.</p><p>One reason maize could have been impacted the most is that it is a "C4" plant (meaning that during photosynthesis it produces a sugar compound that has four carbon atoms), while the other crops are "C3" plants (meaning they produce a sugar that has three carbon atoms).</p><p><a href="https://www.sciencedirect.com/science/article/pii/S0044328X81801675" target="_blank">Research</a> shows that C3 plants require less sunlight to reach optimum levels of photosynthesis than C4 plants—meaning they are likely to be less affected by the solar dimming caused by aerosol release.</p><p><strong>Geoengineered World</strong></p><p>To understand how solar geoengineering could impact crop yields, the researchers applied their results to a <a href="https://www.carbonbrief.org/qa-how-do-climate-models-work" target="_blank">climate model</a>.</p><p>The model looked at changes to crop yields under two future scenarios—one with "moderate" climate change ("<a href="https://link.springer.com/article/10.1007/s10584-011-0151-4" target="_blank">RCP4.5</a>") and one with the same level of emissions, but also an injection of aerosols. The scenario assumes that the amount of aerosols released is enough to offset the temperature change caused by all emissions occurring after 2020.<br></p><p>The modeling results show that, in the solar geoengineering scenario, cooler global temperatures boost average maize yields by 6 percent, when compared to the climate change scenario.</p><p>However, the reduction of direct sunlight in the same scenario reduces maize yields by 5 percent over the same period. Yields are also slightly decreased as a result of the impact of aerosol release on rainfall and cloud cover.</p><p>The findings show that, in comparison to a scenario with climate change alone, solar geoengineering "has no statistically discernible effect on yields once we have accounted for optical effects," the researchers said in their paper.</p><p>The researchers also found that solar geoengineering had an "insignificant" effect on yields of soy, rice and wheat—in comparison to the climate change scenario.</p><p><strong>Food for Thought</strong></p><p>The findings suggest that, on balance, solar geoengineering could "fail" to prevent the damage to global crop yields expected under climate change alone, said Proctor.</p><p>The new research could offer a new avenue for solar geoengineering researchers, said co-author <a href="https://gspp.berkeley.edu/directories/faculty/solomon-hsiang" target="_blank">professor Solomon Hsiang</a>, a policy researcher from the University of California, Berkeley. He told a press briefing:</p><p>"A key innovation of this study was to find a way to study the potential side-effects of geoengineering without actually deploying it."</p><p>However, although the research is "useful and important" to understanding more about how the dimming of sunlight could affect agriculture, it does not provide "solid evidence" of how solar geoengineering would impact crops, said <a href="https://www.seas.harvard.edu/directory/dkeith" target="_blank">professor David Keith</a>, director of the <a href="https://geoengineering.environment.harvard.edu/" target="_blank">Solar Geoengineering Research Program</a> at the <a href="https://www.seas.harvard.edu/" target="_blank">University of Harvard</a>, who was not involved in the research. He told Carbon Brief:</p><p>"Solar geoengineering would likely differ from volcanoes in two crucial respects. First, and most important, solar geoengineering would be a relatively continuous application of aerosols rather than a single pulse that lasts less than a year. The climate response to continuous and pulsed radiative forcing—science speak for dimming the sun—would be very different.</p><p>"Second, most serious proposals for solar geoengineering assume that it would be designed to have roughly even pole-to-pole radiative forcing. A volcano, in contrast, tends to produce a quite asymmetric radiative forcing. That asymmetry again produces a climate response quite different from what would likely happen under solar geoengineering."</p><p>The new research also does not consider how solar geoengineering could influence the occurrence of <a href="http://www.ecowatch.com/tag/extreme-weather">extreme events</a>, such as heatwaves and <a href="http://www.ecowatch.com/tag/drought">droughts</a>, which are likely to be important to crop production, said <a href="http://emps.exeter.ac.uk/mathematics/staff/aj369" target="_blank">Dr. Anthony Jones</a>, a research fellow from the <a href="http://www.exeter.ac.uk/" target="_blank">University of Exeter</a>, who was also not involved in the research. He told Carbon Brief:</p><p>"I suspect that the crop yields are sensitive to changes to extremes – for instance, droughts and heatwaves – that may be ameliorated by SRM and which are not accounted for in this model."</p><p>The methods used by the research team are "interesting" and provide "new results," said <a href="http://people.envsci.rutgers.edu/robock/" target="_blank">professor Alan Robock</a> from the the <a href="http://envsci.rutgers.edu/index.php" target="_blank">department of environmental sciences</a> at <a href="https://newbrunswick.rutgers.edu/" target="_blank">Rutgers University</a>. He told Carbon Brief:</p><p>"But they are based on agricultural practices from 30 years ago. More study of whether modern and future farming, including new equipment, seeds, and fertilizers, would react the same way is needed."</p><p>The study takes an "important" step forward in understanding the potential socio-economic impacts of solar geoengineering, said <a href="http://dccc.iisc.ac.in/balag_home.html" target="_blank">professor Govindasamy Bala</a>, from the <a href="http://dccc.iisc.ac.in/" target="_blank">Divecha Centre for Climate Change</a> at the <a href="http://www.iisc.ac.in/" target="_blank">Indian Institute of Science</a>. He told Carbon Brief:</p><p>"However, I do not think this is the last word on this subject. More similar studies would be needed to narrow down the uncertainty in process modeling."</p><p>Agreeing with Bala, <a href="http://www.cds.caltech.edu/~macmardg/" target="_blank">professor Douglas MacMartin</a>, an engineering researcher from <a href="https://www.engineering.cornell.edu/" target="_blank">Cornell University</a>, who <a href="https://science.house.gov/sites/republicans.science.house.gov/files/documents/HHRG-115-SY18-WState-DMacMartin-20171108.pdf" target="_blank">contributed</a> to a hearing on geoengineering at the U.S. House of Representatives, said the results should provide "motivation" for more research. He told Carbon Brief:</p><p>"The study is important for looking at a possible impact of solar geoengineering that no one has yet explored. But because the data that goes into the study is so limited and so noisy, one shouldn't read too much into it, at least not yet. Instead, this should be taken simply as motivation for doing more research and only reaching conclusions after more studies have looked at this question."</p><p class="shortcode-media shortcode-media-twitter_embed">
</p><div id="057d0" class="rm-shortcode" data-rm-shortcode-id="MOPA241576661898"><blockquote class="twitter-tweet twitter-custom-tweet" data-twitter-tweet-id="955560842870906880" data-partner="rebelmouse"><div style="margin:1em 0">Geoengineering Carries ‘Large Risks’ for the Natural World, Studies Show https://t.co/9qRf9bmSTp @ClimateDesk @worldresources @OneWorld_News</div> — EcoWatch (@EcoWatch)<a href="https://twitter.com/EcoWatch/statuses/955560842870906880">1516658433.0</a></blockquote></div>
<p></p><p><em>Reposted with permission from our media associate <a href="https://www.carbonbrief.org/solar-geoengineering-could-fail-to-prevent-damate-to-crop-yields" target="_blank">Carbon Brief</a>.</em><br></p>
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Moon with orange-colored troposphere band, the lowest and most dense portion of the earth's atmosphere. NASA
By Daisy Dunne
Scientists studying the troposphere—the lowest level of the atmosphere—have found "powerful evidence" that climate change is altering seasonal temperatures.
A study published in Science finds that climate change has caused an increase in the difference between summer and winter temperatures across North America and Eurasia over the past four decades.
<p>This could be the result of summer temperatures warming at a faster rate than winter temperatures in these parts of the world, the researchers say.</p><p>The findings show the "substantial human influence on Earth's climate, affecting not only global averages, but also local and seasonal changes," another scientist says.</p><p>Most of the world's weather originates in the troposphere, a second scientist tells Carbon Brief, meaning that changes to seasonal temperatures could be affecting the likelihood of <a href="http://www.ecowatch.com/tag/extreme-weather">extreme weather</a> events, such as <a href="http://www.ecowatch.com/tag/flooding">flooding</a> and <a href="http://www.ecowatch.com/tag/drought">drought</a>.</p><p><strong>Sky High</strong></p><p>Evidence shows that the seasons are changing. In Europe, for example, <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2486.2006.01193.x" target="_blank">analysis</a> of the first-emergence dates of more than 500 plant species shows that the first day of spring has advanced by six to eight days in the past three decades.</p><p>However, working out to what extent seasonal changes can be explained by climate change—rather than natural climate variability, caused by phenomena such as <a href="https://www.carbonbrief.org/category/science/extreme-weather/el-nino" target="_blank">El Niño</a>—presents more of a challenge.<br></p><p>To quantify the influence of climate change versus natural variability, scientists often carry out "<a href="https://www.carbonbrief.org/category/science/extreme-weather/attribution" target="_blank">attribution</a>" studies.</p><p>The new study is the first to assess how climate change could be influencing seasonal temperature changes in the troposphere—a layer that covers roughly the first 17 kilometers (approximately 10.6 miles) of the atmosphere above the earth.</p><p>Writing in their research paper, the team, led by <a href="https://pcmdi.llnl.gov/staff/santer/index.html" target="_blank">Dr. Ben Santer</a>, a scientist at the <a href="https://www.llnl.gov/" target="_blank">Lawrence Livermore National Laboratory</a>, said:</p><p>"Our results suggest that attribution studies with the changing seasonal cycle provide powerful evidence for a significant human effect on Earth's climate."</p><p><strong>Satellite Sentinels</strong></p><p>For the study, the researchers analyzed atmospheric temperature data recorded by <a href="https://www.carbonbrief.org/interactive-satellites-used-monitor-climate-change" target="_blank">satellites</a> throughout the summer and winter months from 1979-2016. (<a href="https://www.carbonbrief.org/explainer-how-surface-and-satellite-temperature-records-compare" target="_blank">Carbon Brief</a> has published an explainer on how satellite temperature records compare with measurements at the earth's surface.)</p><p>The map below shows how the difference between summer and winter temperatures, expressed as an average per decade, has changed across the world.</p><p>On the map, dark red indicates where the difference between summer and winter temperatures have grown larger, while dark blue shows where the difference has grown smaller.</p><p class="shortcode-media shortcode-media-rebelmouse-image">
<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xODIwNzAyNi9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTYxMDYyMTE5N30.gTx6strVJRiKo3O-NW94xwG3s54sEYHS-3byX6Etncs/img.png?width=980" id="7033f" class="rm-shortcode" data-rm-shortcode-id="f44090ec7ac75834201c3205ae08e3c2" data-rm-shortcode-name="rebelmouse-image">
<small class="image-media media-caption" placeholder="add caption...">Temperature difference between summer and winter months (per decade) from 1979-2016. Red shows a large temperature difference between the seasons, while blue shows a small temperature difference. </small><small class="image-media media-photo-credit" placeholder="add photo credit...">Source: Randel (2018) Data source: Santer et al. (2018)</small></p><p>The map shows that the difference between summer and winter temperatures has increased the most in mid-latitude regions, particularly in the northern hemisphere.<br></p><p>This is because, in these regions, atmospheric summer temperatures are increasing at a faster rate than winter temperatures—causing the disparity between the two seasons to grow larger and larger, the researchers say.</p><p>The northern hemisphere has experienced more summertime warming than the southern hemisphere because it contains more land, the researchers say. The presence of land means that less heat can be absorbed by the ocean—leading to amplified atmospheric warming.</p><p>The map also indicates that the eastern edges of both North America and Eurasia have experienced the greatest amounts of warming. This could be because, during the winter in these regions, warm air masses are carried from east to west—leading to milder winters along western continental margins, the researchers say.</p><p>Changes in temperatures are not as pronounced around the tropics because this region is not highly seasonal, the researchers say. Instead, the seasons in tropical regions are typically defined by rainfall ("wet" and "dry," for example), rather than by temperature.</p><p>In contrast, the difference between summer and winter temperatures around the poles has shrunk over the past four decades, the map shows. In these regions, winter temperatures are rising faster than summer temperatures, the research finds.</p><p>In the <a href="http://www.ecowatch.com/tag/arctic">Arctic</a>, this winter warming is partly influenced by the <a href="https://www.carbonbrief.org/arctic-sea-ice-summer-minimum-2017-eighth-lowest-record" target="_blank">diminishing presence</a> of <a href="http://www.ecowatch.com/tag/sea-ice">sea ice</a> during summer months, the researchers say. With less sea ice present, the <a href="https://www.ecowatch.com/tag/oceans">ocean</a> absorbs more heat—which is later released during the winter, the researchers say.</p><p>The reason that winter atmospheric warming may have accelerated above <a href="http://www.ecowatch.com/tag/antarctica">Antarctica</a> is less clear. However, <a href="https://rmets.onlinelibrary.wiley.com/doi/full/10.1002/asl.237" target="_blank">previous research</a> suggests that the presence of polar clouds in the stratosphere (which sits above the troposphere) could be playing a role.</p><p><strong>'Substantial Human Influence'</strong></p><p>To understand to what extent the observed seasonal changes were influenced by human-caused climate change, the researchers compared the satellite results to <a href="https://www.carbonbrief.org/qa-how-do-climate-models-work" target="_blank">climate models</a>.</p><p>The model simulations, which ran from 1979-2016, included a range of natural factors that can influence tropospheric temperature, including the cooling effect of <a href="https://www.carbonbrief.org/analysis-how-could-agung-volcano-bali-affect-global-temperature" target="_blank">volcanic eruptions</a> and <a href="https://www.carbonbrief.org/aerosols-dampen-pace-of-arctic-warming-for-now-say-scientists" target="_blank">aerosols</a>. To include the impact of human-caused climate change, the researchers used a "business-as-usual" emissions scenario known as <a href="https://link.springer.com/article/10.1007/s10584-011-0149-y" target="_blank">RCP8.5</a>.<br></p><p>The results show that only simulations that include the impact of human-caused climate change could correctly predict the patterns of seasonal temperature change recorded by the satellites.</p><p>This indicates that humans are having a "substantial influence" on the temperatures in the troposphere, said <a href="https://staff.ucar.edu/users/randel" target="_blank">Dr. William Randel</a>, a senior scientist at the <a href="https://ncar.ucar.edu/" target="_blank">National Center for Atmospheric Research</a>, who was not involved in the research. In an accompanying perspectives article, he writes:</p><p>"[The] findings provide further markers of a substantial human influence on Earth's climate, affecting not only global averages, but also local and seasonal changes."</p><p><strong>Weather Worries</strong></p><p>However, it is not clear how temperature changes in the troposphere could affect conditions at the land surface, he adds:</p><p>"The connection between changes at the surface and the free troposphere awaits explanation."</p><p>One possible effect could be changes to the timing and likelihood of extreme weather events, said <a href="https://www.cranfield.ac.uk/people/professor-neil-harris-758415" target="_blank">professor Neil Harris</a>, head of the Centre for Environment and Agricultural Informatics at <a href="https://www.cranfield.ac.uk/" target="_blank">Cranfield University</a>, who was not involved in the research. He told Carbon Brief:</p><p>"The paper significantly increases confidence that the observed changes in the troposphere—where all our weather is—are consistent with models and that they are of human origin. This gives more confidence in the existing findings of an increase frequency of extreme weather, such as more intense rainfall and more extreme summer hot spells."</p><p class="shortcode-media shortcode-media-twitter_embed">
</p><div id="cdbaf" class="rm-shortcode" data-rm-shortcode-id="LU01Y21576662373"><blockquote class="twitter-tweet twitter-custom-tweet" data-twitter-tweet-id="899621857464389633" data-partner="rebelmouse"><div style="margin:1em 0">Solar Eclipse: Why the Sun Is Not Responsible for Recent Climate Change https://t.co/LukE7BHXKE #SolarEclipse2017 #Eclipse2017 @NASA @SpaceX</div> — EcoWatch (@EcoWatch)<a href="https://twitter.com/EcoWatch/statuses/899621857464389633">1503321539.0</a></blockquote></div>
<p></p><p><em>Reposted with permission from our media associate <a href="https://www.carbonbrief.org/powerful-evidence-global-warmings-effect-seasons-found-troposphere" target="_blank">Carbon Brief</a>.</em><br></p>
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Martin Pickard / Getty Images
By Simon Evans
There could be as many as 36m electric vehicles (EVs) on UK roads by 2040, double the number expected just a year ago.
<p>That's according to the latest National Grid <a href="http://fes.nationalgrid.com/" target="_blank">Future Energy Scenarios</a>, published today. Yet despite raising electricity demand, National Grid now said the rapid rise of EVs will help the UK shift towards more renewable and low-carbon electricity generation.</p><p>Smart charging and vehicle-to-grid technology means EVs will be able to help smooth electricity usage through the hours of the day, National Grid said. They will be able to charge mainly when demand is low and even feed back into the grid when demand is high.</p><p>"Growth in EVs supports the continued trend towards more low-carbon generation," said National Grid. "[They] will be able to support the continued growth in renewables by storing excess generation and releasing it back onto the network when it is needed."</p><h4>Future Energy Scenarios</h4><p>Each year, National Grid publishes a set of four scenarios for the UK's future energy supply and demand built around the company's own modelng and consultation with the energy community. The scenarios help the company plan for an uncertain—but rapidly changing—energy system.</p><p>Fintan Slye, director, UK system operator at National Grid wrote in a foreword:</p><blockquote>"It's impossible to accurately forecast a single energy future over the long term. However, creating a range of credible futures allows us to continue supporting the development of an energy system that's robust against different outcomes."<br></blockquote><p>This year's scenarios include a stronger focus on the UK's transition to low-carbon. "We've refreshed our scenario framework to reflect the increasing importance of decentralization and decarbonization in our industry," Slye wrote.</p><p>Nevertheless, only two of the four scenarios meet the UK's legally binding greenhouse gas emissions target for 2050—an 80 percent cut on 1990 levels. This target is <a href="https://www.carbonbrief.org/analysis-uk-to-seek-advice-on-strengthening-long-term-climate-goal" target="_blank">likely to be raised</a> in response to the 2015 <a href="https://www.carbonbrief.org/interactive-the-paris-agreement-on-climate-change" target="_blank">Paris agreement</a>. These points form important context for National Grid's conclusions.</p><p>In previous years, only one of the four scenarios met the UK's 2050 target.</p><h4>Twice as Many EVs</h4><p>One of the most striking changes in this year's scenarios is the much more rapid adoption of EVs. This can be seen in the chart, below, which compares scenarios that meet the 2050 target and were published in each year between 2013 and 2018.</p>
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<a href="https://www.carbonbrief.org/rise-uk-electric-vehicles-national-grid-doubles-2040-forecast" target="_blank"><img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xODE4MDc1MS9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTY0ODE1MDIxOX0.mjVdIwJ2N-jJWVHDJq8za_Bdz-AJD6MOsrPH7InG2OY/img.png?width=980" id="ffeb3" class="rm-shortcode" data-rm-shortcode-id="c742ab8ccb4f627ed7d40f8b1739be95" data-rm-shortcode-name="rebelmouse-image"></a>
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<p><em>Above: Number of EVs on UK roads in National Grid scenarios published between 2013 and 2018. Source: "Gone Green" or "Two Degrees" Future Energy Scenarios 2013-2018. Chart by Carbon Brief using <a href="https://www.highcharts.com/" target="_blank">Highcharts</a><span></span></em></p><p>Between 2013 and 2015, National Grid consistently said there would be around 5m EVs on UK roads by 2035. It raised that 2035 outlook to 8m in its 2016 work, rising to 10m in 2040, as <a href="https://www.carbonbrief.org/national-grid-sees-major-boost-for-solar-electric-vehicles-and-batteries" target="_blank">Carbon Brief</a> reported at the time. The outlook grew again last year to 13m in 2035 and 17m in 2040.<br></p><p>This year, National Grid said there could be up to 25m EVs by 2035 and 36m by 2040, effectively doubling its outlook from last year. The figures represent a tripling compared to 2016's figures and a five-fold increase from the 2015 numbers. By 2040, National Grid now said EVs will reach saturation point, with all possible vehicles electrified and new EVs replacing old ones as they retire.</p><p>A June 2018 <a href="https://gallery.mailchimp.com/d919930dfbffc8e4d3684958d/files/3b213b3e-618c-4f94-b5b0-ba350782067c/Transport_model.pdf?mc_cid=ef83cb1e08&mc_eid=12a11134c0" target="_blank">brief on transport modeling</a> said:</p><blockquote>"We have been working hard to develop a much more holistic road transport model that takes into account the whole cost of ownership of vehicles. Our new model is much more granular in its detail and consequently it is more robust than previous ones."<br></blockquote><p>The increase in outlook also reflects the government's <a href="https://twitter.com/DrSimEvans/status/1016273277122117632" target="_blank">somewhat weakened</a> pledge to <a href="https://www.carbonbrief.org/analysis-switch-to-electric-vehicles-would-add-just-10-per-cent-to-uk-power-demand" target="_blank">ban conventional</a> petrol and diesel cars by 2040.</p><h4>Charging Habits</h4><p>The same June brief explains how National Grid has been working to understand the way that people will use and charge EVs. The electrification of transport—and, potentially, also heat—is set to raise UK demand for electricity, meaning more generating capacity will need to be built.</p><p>Last year, National Grid's earlier work on the impact of this new electricity demand was <a href="https://www.carbonbrief.org/factcheck-how-much-power-will-uk-electric-vehicles-need" target="_blank">widely misreported</a> as showing that the transition to EVs would be unmanageable. Since then, it has been working to expand its evidence base and to more realistically explore the impact of EVs.</p><p>The brief explained:</p><blockquote>"We have been gathering large amounts of evidence to help us formulate views on some of the more uncertain variables associated with vehicle use and charging preferences. The 'how and what' type of chargers that people use is all being considered.<br></blockquote><p>"We anticipate that most consumers will avoid peak time charging although some may still choose to do so. Vehicle to Grid technology is also a new input into our model … In our scenarios, we show that this is going to have significant impacts on the energy landscape of the future."</p><p>Combining these new insights on deeper EV penetration, smarter charging and vehicle-to-grid, National Grid now says peak electricity demand could be increased by between 3-8 gigawatts (GW in 2030 (4-14 percent) and by 3-13GW in 2050 (6-22 percent). This is shown in the chart, below.</p>
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<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xODE4MDc0My9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTYxMDc5NTcyOX0.EKbZVuK9-bXtf9qPkzBLM-Bdge1HzlE7Mbim7eKvDtM/img.png?width=980" id="02235" class="rm-shortcode" data-rm-shortcode-id="1da92b2f2aed39633be81e38c57bbc71" data-rm-shortcode-name="rebelmouse-image">
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<p><em>Above: Net increase in peak UK electricity demand due to electric vehicles, in four different scenarios. Note that only "Community Renewables" and "Two Degrees" meet the UK's current climate goal for 2050. V2G is vehicle-to-grid. Source: </em><a href="https://www.nationalgrid.com/uk/publications/future-energy-scenarios-fes" target="_blank"><em>National Grid Future Energy Scenarios 2018</em></a><span></span></p><p>These ranges can be compared to last year's future energy scenarios, which saw 2050 peak demand increasing by at least 6GW and as much as 30GW as a result of EVs. The top end of this range assumed that all charging was "dumb," taking place during peaks. National Grid now thinks the majority of chargers will be "smart," enabling most consumers to shift demand off-peak.<br></p><p>Note that the largest increases in 2050 peak demand are in scenarios that do not meet the 2050 carbon target ("Steady Progression" and "Consumer Evolution"). The target-compliant scenarios ("Community Renewables" and "Two Degrees") see earlier increases in peak demand, due to more rapid uptake of EVs, but also faster adoption of vehicle-to-grid technology.</p><p>The main difference between the two target-compliant scenarios is what National Grid calls "engagement." This reflects whether consumers choose to charge their EVs during peak demand or whether lower tariff prices encourage them to charge during periods of low demand.</p><p>(More broadly, the shift to EVs will reduce energy demand, as they are more efficient than combustion-engine vehicles. An <a href="https://www.carbontracker.org/ev-oil-demand-displacement-tool/" target="_blank">interactive tool</a> developed by the Carbon Tracker Initiative shows how much EV adoption will cut into global oil demand.)</p><h4>Balancing the Grid</h4><p>This year's report says the use of smart chargers and vehicle-to-grid technology means EVs can "supports the continued trend towards more low-carbon generation" by smoothing supply and demand.</p><p>Smart charging shifts "engaged" consumers to use off-peak electricity for their EVs (shown in the orange areas of the chart, below). Vehicle-to-grid technology charges EVs using off-peak electricity then feeds it back into the grid at times of peak demand (red areas).</p>
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<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xODE4MDczOS9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTYzODAyMjg4OH0.kxaD47cb2jRT_vXmCIdkkc_czo-R4CB2fPoiqRUYWus/img.png?width=980" id="dde6c" class="rm-shortcode" data-rm-shortcode-id="84dd32121901dc53dad84a8944639005" data-rm-shortcode-name="rebelmouse-image">
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<p><em>Above: EV charging impact on UK electricity demand through the hours of each day. Blue: Non-transport demand. Purple: EV charging by "unengaged" consumers, adding to peak demand. Orange: Off-peak EV charging by "engaged" consumers. Red: Vehicle-to-grid technology that shifts demand from peak to off-peak periods. Source: <a href="https://www.nationalgrid.com/uk/publications/future-energy-scenarios-fes" target="_blank">National Grid Future Energy Scenarios 2018</a><span></span></em></p><p><span></span>National Grid said a range of commercial developments support its updated views on EV charging behavior: "A number of energy suppliers have launched EV specific tariffs that have a time of use element [pricing to encourage off-peak charging]."<br></p><p>There have also been innovations and trials in vehicle-to-grid technology, it added.</p><p> <em>Reposted with permission from our media associate <a href="https://www.carbonbrief.org/rise-uk-electric-vehicles-national-grid-doubles-2040-forecast" target="_blank">Carbon Brief</a>.</em><em></em></p>
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