Black Carbon Larger Cause of Climate Change Than Previously Assessed
By Ellen Baum
Thirteen years after Jim Hansen described the significant role of black carbon for climate stabilization,1 in a comprehensive assessment of black carbon and climate released on Jan. 15, a team of 31 worldwide experts have confirmed the importance to combating global warming by reducing black carbon from targeted pollution sources.
Schematic overview of the primary black carbon emission sources and the processes that control the distribution of black carbon in the atmosphere and determine its role in the climate system [Bond et al., 2013].
The authors of the study, Bounding the role of black carbon in the climate system: A scientific assessment, have developed a best estimate of black carbon’s direct influence on atmospheric warming that is almost two times higher than most previous work, including the estimates in the last Intergovernmental Panel on Climate Change (IPCC)—from 0.34 W/m2 (0.27°C) to +0.71 W/m2 (0.57 °C)2.
The Clean Air Task Force (CATF) welcomes this paper, which was four years in the making and adds more certainty to a number of questions about the effectiveness of controlling black carbon as a climate mitigation strategy. A particular thorny issue—the effects of black carbon on clouds—remains complicated, but the study concluded that black carbon is not having a strong cooling influence on clouds, which strengthens the case for mitigation efforts. When all effects of black carbon are included i.e., the effects on snow and clouds, the best estimate of the climate forcing impact of black carbon is stronger than previous estimates—at a total forcing: 1.1 W/m2 (0.88 °C) or two-thirds of the warming to date from CO2.
The assessment also confirms that black carbon causes significantly higher warming over the Arctic from a combination of the warming effect on the atmosphere and the additional effect of black carbon darkening snow and accelerating the melting of Arctic snow and ice.
Although the study bolsters the case that black carbon is a powerful global warming agent, it also corroborates previous analyses that mitigation actions must be carefully targeted to certain pollution sources for maximum effectiveness. Black carbon is emitted by the incomplete combustion of fuel and emitted with a mixture of gases and aerosols that both warm and cool over the short and long term.
Reductions will be most climate beneficial depending on that mix of emissions composition other aerosols such as organic carbon and gases, including sulfur dioxide, oxides of nitrogen and carbon dioxide as well as location of the source of pollution. The study looks closely at the best-known sources of black carbon and their total impacts to the climate and identifies diesel engines, brick kilns and residential cook stoves as the most promising sources for mitigation.
CATF has been working to navigate a defensible scientific and action roadmap to first understand and then win reductions from black carbon-rich sources. Guided by the previous work of the study’s authors, CATF has worked for nearly a decade to advocate for effective policies to reduce black carbon emissions including:
- Coordinating the U.S. diesel campaign to win retrofits of existing, dirty diesel engines with emissions controls that can reduce black carbon emissions by more than 90 percent, arguing for the climate benefits that could come with retrofitted engines.
- Working in the Arctic to reduce sources of black carbon from flaring from oil and gas operations and agricultural fires.
- Advocating for controls on ships traveling in and near Arctic waters through actions at the International Maritime Organization.
- Supporting research to measure black carbon in Arctic and seasonal snow packs
- Funding the only measurements of black carbon from traditional and modern brick kilns and collaborating on brick modernization activities in India and through the Climate and Clean Air Coalition in other regions and countries.
Based on the new evidence in today’s study, there are a number of actions to push for to quickly reduce black carbon. The U.S. should demonstrate leadership on black carbon by advancing policies that reduce emissions from the large fleet of older diesel vehicles in the U.S. and from natural gas systems. Measures include:
- Fully funding the Diesel Emission Reduction Act (DERA) to support diesel vehicle and equipment retrofits that achieve vital black carbon reductions.
- Reducing the excise tax on new diesel engines to accelerate fleet turnover.
- Regulations to reduce emissions from flaring associated with the oil and gas industry.
The U.S. should also call for:
- Faster adoption of tighter diesel vehicle emission standards internationally, which will promote the global deployment of advanced U.S. diesel engine technologies.
- Faster global deployment of flaring technologies for natural gas systems to achieve complete combustion of flared gas.
- Greater public-private partnerships and multinational collaboration (e.g. the State Department’s Climate and Clean Air Coalition or the Arctic Council).
- Adoption of controls for shipping in and near Arctic waters through the International Maritime Organization.
International opportunities include:
- In 2011 the Arctic Council called upon nations to reduce black carbon emissions from in and near Arctic sources3; now Arctic nations should take active steps to adopt those actions.
- There are transitional and transformative opportunities for brick modernization for the 1.5 trillion bricks produced worldwide each year, affording cost-effective opportunities for countries and industries to upgrade. More than 80 percent of brick operations are in Asia.
The best news is that all of these are targeted sources in the Bounding paper. Further, the paper gives us—and others—the confidence to keep our shoulder at the wheel, knowing that we are making even greater inroads with this work than we thought when we were inspired to get started.
Visit EcoWatch’s ENERGY page for more related news on this topic.
1 Hansen, J.E. et. al. Global warming in the twenty-first century: An alternative scenario, PNAS, August 29, 2000 97 (18) 9875–9880
2 The conversion of radiative forcing to temperature depends on climate sensitivity. Here we assume 1 W/m2=0.8°C
3 ,Technical report of the Arctic Council Task Force on Short-Lived Climate Forcers, May 11, 2011
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By D. André Green II
One of nature's epic events is underway: Monarch butterflies' fall migration. Departing from all across the United States and Canada, the butterflies travel up to 2,500 miles to cluster at the same locations in Mexico or along the Pacific Coast where their great-grandparents spent the previous winter.
Millions of People Care About Monarchs<p>I will never forget the sights and sounds the first time I visited monarchs' overwintering sites in Mexico. Our guide pointed in the distance to what looked like hanging branches covered with dead leaves. But then I saw the leaves flash orange every so often, revealing what were actually thousands of tightly packed butterflies. The monarchs made their most striking sounds in the Sun, when they burst from the trees in massive fluttering plumes or landed on the ground in the tussle of mating.</p><p>Decades of educational outreach by teachers, researchers and hobbyists has cultivated a generation of monarch admirers who want to help preserve this phenomenon. This global network has helped restore not only monarchs' summer breeding habitat by planting milkweed, but also general pollinator habitat by planting nectaring flowers across North America.</p><p>Scientists have calculated that restoring the monarch population to a stable level of about 120 million butterflies will require <a href="https://doi.org/10.1111/icad.12198" target="_blank">planting 1.6 billion new milkweed stems</a>. And they need them fast. This is too large a target to achieve through grassroots efforts alone. A <a href="https://www.fws.gov/savethemonarch/CCAA.html" target="_blank" rel="noopener noreferrer">new plan</a>, announced in the spring of 2020, is designed to help fill the gap.</p>
Pros and Cons of Regulation<p>The top-down strategy for saving monarchs gained energy in 2014, when the U.S. Fish and Wildlife Service <a href="https://www.fws.gov/southeast/pdf/petition/monarch.pdf" target="_blank">proposed</a> listing them as threatened under the Endangered Species Act. A decision is expected in December 2020.</p><p>Listing a species as endangered or threatened <a href="https://www.fws.gov/endangered/esa-library/pdf/listing.pdf" target="_blank">triggers restrictions</a> on "taking" (hunting, collecting or killing), transporting or selling it, and on activities that negatively affect its habitat. Listing monarchs would impose restrictions on landowners in areas where monarchs are found, over vast swaths of land in the U.S.</p><p>In my opinion, this is not a reason to avoid a listing. However, a "threatened" listing might inadvertently threaten one of the best conservation tools that we have: public education.</p><p>It would severely restrict common practices, such as rearing monarchs in classrooms and back yards, as well as scientific research. Anyone who wants to take monarchs and milkweed for these purposes would have to apply for special permits. But these efforts have had a multigenerational educational impact, and they should be protected. Few public campaigns have been more successful at raising awareness of conservation issues.</p>
<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="91165203d4ec0efc30e4632a00fdf57d"><iframe lazy-loadable="true" src="https://www.youtube.com/embed/KilPRvjbMrA?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span>
The Rescue Attempt<p>To preempt the need for this kind of regulation, the U.S. Fish and Wildlife Service approved a <a href="https://www.fws.gov/savethemonarch/pdfs/Monarch%20CCAA-CCA%20Public%20Comment%20Documents/Monarch-Nationwide_CCAA-CCA_Draft.pdf" target="_blank">Nationwide Candidate Conservation Agreement for Monarch Butterflies</a>. Under this plan, "rights-of-way" landowners – energy and transportation companies and private owners – commit to restoring and creating millions of acres of pollinator habitat that have been decimated by land development and herbicide use in the past half-century.</p><p>The agreement was spearheaded by the <a href="http://rightofway.erc.uic.edu/" target="_blank">Rights-of-Way Habitat Working Group</a>, a collaboration between the University of Illinois Chicago's <a href="https://erc.uic.edu/" target="_blank" rel="noopener noreferrer">Energy Resources Center</a>, the Fish and Wildlife Service and over 40 organizations from the energy and transportation sectors. These sectors control "rights-of-way" corridors such as lands near power lines, oil pipelines, railroad tracks and interstates, all valuable to monarch habitat restoration.</p><p>Under the plan, partners voluntarily agree to commit a percentage of their land to host protected monarch habitat. In exchange, general operations on their land that might directly harm monarchs or destroy milkweed will not be subject to the enhanced regulation of the Endangered Species Act – protection that would last for 25 years if monarchs are listed as threatened. The agreement is expected to create up to 2.3 million acres of new protected habitat, which ideally would avoid the need for a "threatened" listing.</p>
A Model for Collaboration<p>This agreement could be one of the few specific interventions that is big enough to allow researchers to quantify its impact on the size of the monarch population. Even if the agreement produces only 20% of its 2.3 million acre goal, this would still yield nearly half a million acres of new protected habitat. This would provide a powerful test of the role of declining breeding and nectaring habitat compared to other challenges to monarchs, such as climate change or pollution.</p><p>Scientists hope that data from this agreement will be made publicly available, like projects in the <a href="https://www.fws.gov/savethemonarch/MCD.html" target="_blank">Monarch Conservation Database</a>, which has tracked smaller on-the-ground conservation efforts since 2014. With this information we can continue to develop powerful new models with better accuracy for determining how different habitat factors, such as the number of milkweed stems or nectaring flowers on a landscape scale, affect the monarch population.</p><p>North America's monarch butterfly migration is one of the most awe-inspiring feats in the natural world. If this rescue plan succeeds, it could become a model for bridging different interests to achieve a common conservation goal.</p>
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