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July 26, 2011

Fixing Black Carbon / Soot pollution will save lives and reduce global warming

The Center for Biological Diversity today notified the Environmental Protection Agency of its intent to file a lawsuit against the agency for its failure to take action to reduce black carbon, a potent global warming pollutant. Last year, the Center filed a formal petition asking the EPA to set water-quality criteria for black carbon, or soot, to help protect sea ice and glaciers under the Clean Water Act. Today’s notice of intent to sue urges the agency to respond promptly to the Center’s petition.

NBF - Supports effort to control, reduce and eliminate black carbon (soot). Some of the most effective interventions are cheap soot free cookers for India that would avoid the equivalent of one ton of CO2 for $6. It could also avoid a loss of a disability-adjusted life year (DALY) for $600 by preventing disease from indoor air pollution.

Black carbon (soot) is not a gas but a particulate — a component of soot emitted by the incomplete combustion of fossil fuels and biomass. By some estimates, emissions from black carbon vie with methane as the second largest contributor to global warming after CO2 emissions. The largest source of black carbon in developed countries such as the United States is diesel fuel.

Black carbon is generally thought to have both a direct warming effect (by absorbing incoming solar radiation in the atmosphere and converting it to heat radiation) and an indirect warming effect (by reducing the reflectivity of snow and ice). Yet it has not been addressed by international or national global warming regulations. Depending on the region, the atmospheric residence time for black carbon emissions from different regions varies between 4.6 to 7.3 days — in other words, it stays in the air for a period of days to weeks instead of more than a hundred years, as is the case with CO2.


In the Arctic, the most crucial climate-change battleground in the short term, black carbon appears to cause more warming than any other agent except CO2 because of its combined heating of the Arctic atmosphere and the surface. Recent studies suggest black carbon is one of the important contributors to the retreat of Arctic sea ice. On timescales of days to weeks, northern Eurasia is the strongest source of Arctic air pollution, especially in the lower troposphere; b lack carbon emissions from northern Eurasia, North America, and Asia have the greatest absolute impact on Arctic warming.

Globally, the United States is responsible for about 6.1 percent of total fossil fuel and biofuel soot emissions. The warming due to U.S. soot exceeds the warming due to either methane or nitrous oxide, making biofuel soot potentially the second leading source of U.S. global warming emissions overall. As snow and ice surfaces continue to warm, melt, darken, and lose contrast with black carbon, the net warming effect of black carbon on the Arctic will decrease. That means that reducing black carbon now will have more of an impact than delaying reductions.

Black carbon emissions come mainly from four sources: 1) diesel engines for transportation and industrial use; (2) residential solid fuels such as wood and coal; (3) open forest and savanna burning, both natural and initiated by people for land clearing; and (4) industrial processes, usually from small boilers.

Globally, reducing black carbon will mean reducing prescribed burns in eastern Europe so that black carbon emission and depositing does not occur in spring as radiation is increasing and the area of snow/ice pack is large. In South Asia, the majority of soot emissions come from biofuel cooking, whereas in East Asia, coal combustion for residential and industrial uses plays a larger role. Providing alternative energy-efficient and smoke-free cookers and introducing transferring technology for reducing soot emissions from coal emissions in small industries could have major impacts on the contributions made to global warming by soot. Improved cookstove programs in China have been successful, and both pilot and full-scale projects have been conducted by the Partnership for Clean Indoor Air and the Shell Foundation. These programs can also be linked to substantial health benefits.

The use of certain cleaner fuels must also be promoted, especially in developing countries: Distillate fuels, such as kerosene and LPG, burn cleaner than solid fuels like charcoal.

A Perspective Paper on Black Carbon Mitigation as a Response to Climate Change (22 pages)

Black Carbon (BC) aerosols have recently been identified as important contributors to
radiative forcing on the global climate. BC reductions – especially those related to contained combustion – provide a win-win opportunity with both health and climate benefits. Emissions from contained combustion are responsible for a total of about 2 million deaths annually in the developing world. There is also a compelling case for their inclusion in a climate emission reductions regime because of their large abatement potential (~15% of current excess radiative forcing), as well as short-term timing considerations (“buying” a delay of ~10 years as part of a climate mitigation strategy). It is important, however, to recognize that BC reductions are not a substitute for reductions in emissions of CO2. The two approaches must be applied together to stabilize atmospheric concentrations of CO2 to acceptable levels of risk. We assess benefit-cost ratios for five different options to reduce BC emissions. Indoor combustion sources of BC such as clean burning household stoves using biomass or gaseous fossil fuels provide the greatest benefit per unit cost. Repair of super-emitting diesel vehicles may also have a benefit-cost ratio greater than one.

BMT note that “40% of current net warming (10-20% of gross warming)” is related to BC. Since use of net warming is scientifically inaccurate and inflates the role that BC plays 1, the attribution of between 10 and 20% of excess warming is more appropriate and consistent with other studies. Specifically, of the 2 ˚C rise in global mean temperature since pre-industrial times (from circa 1760), BC’s contribution is approximately 0.3 ˚C (Jacobson, 2004; Bice et al., 2009). To the first order, eliminating current BC sources should reduce excess temperature forcing by about 15%.

28 pages on the petition to the EPA to regulate black carbon

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