Copenhagan Close-Up: Black Carbon – small particle, big problem

Stephen Smith | December 18, 2009 | Clean Transportation, Climate Change, Energy Policy

This post was co-authored by John Wilson, Laura Wilson and Anne Blair

Being so close to the Arctic here in Copenhagen, I have been listening carefully to what people have to say about the melting of the polar ice cap. While scientists still agree that carbon dioxide is the major driver of global warming, nearly half of the warming that has affected the Arctic over the past three decades may be attributed to black carbon, or soot.

One striking finding is that most black carbon impacts in the Arctic come from North America, according to a draft white paper by an ad hoc working group led by many of the leading scientists in this field. Climate scientists study black carbon using studies of black carbon emissions around the world, models of their transport and impact on the atmosphere, and temperature trends in the Arctic.

The regions of Earth that showed the strongest responses to aerosols in the model are the same regions that have witnessed the greatest real-world temperature increases since 1976. The Arctic region has seen its surface air temperatures increase by 1.5°C (2.7°F) since the mid-1970s. In the Antarctic, where aerosols play less of a role, the surface air temperature has increased about 0.35°C (0.6°F).

From a global perspective, however, North America isn’t the dominant culprit, as black carbon sources and impacts are linked in unexpected ways. North America contributes 5-10% of global black carbon emissions, according to papers by Koch et al and Reddy et al. For example, black carbon found over the Atlantic Ocean has been mostly linked to Southeast Asia, demonstrating the regional patterns of emissions are quite complex.

On a pound-for-pound basis, as black carbon is 200 times more potent than CO2 and warms the climate by absorbing sunlight and heat, it is a powerful greenhouse actor. Because of its dark color, black carbon works double time, warming the atmosphere while suspended in the air, and accelerating snow and ice melt where it settles on snow and the ground.

Unlike other global warming pollutants, black carbon falls out of the atmosphere quite quickly. According to Bond, a leading researcher on the subject, “reducing all aerosols from major sources of black carbon will reduce direct climate warming with a very high probability,” and, I might add, more quickly than many other options.

Health effects of black carbon (soot)

Black carbon is a killer. “Combustion-related air pollution is estimated to be responsible for nearly 2.5 million premature deaths annually around the world,” according to Kirk Smith, a lead author in a recent Lancet series on Health and Climate Change.

The North American contribution to global black carbon emissions is not expected to grow over the next forty years. Similarly, global emissions of black carbon are likely to decline somewhat. But while today’s laws are expected to help us tomorrow, more can and should be done.

Opportunity for global leadership

One of the driving forces in the downward trend in global black carbon emissions is advanced pollution control technology. Yesterday, US Secretary of State Hillary Clinton made a welcome announcement that the United States “will pay its fair share of $100 billion annually by 2020 to assist poor countries in coping with climate change.”

Left unsaid was exactly what the funds would be directed towards (and how much of the $100 billion the US would contribute). One great target for the funds would be reductions in global emissions of black carbon. It may be hard to believe, but cookstoves in developing countries are among the significant sources of black carbon, and may be part of what is melting glaciers in the Himalayas.

Action at home in the Southeast


The connection between a cookstove in a mud hut in India and the diesel exhaust that choked you on the street this afternoon? Technology. We’ve been impressed with demonstrations of cleaner cookstoves and as you may know, Southern Alliance for Clean Energy has been working to reduce diesel exhaust using technologies that can reduce soot by up to 90%.

New school buses, construction equipment and other diesel engines are getting cleaner due to Clean Air Act regulations and the federal Diesel Emissions Reduction Act which passed in 2005 (and which we supported). SACE helped pass state funding legislation for diesel retrofits in both North Carolina and Georgia. We also have started Clean Energy Biofuels our company that makes sustainable biodiesel from waste vegetable oil.

Today, we are also motivated to accelerate the reduction of black carbon emissions as a vital step in slowing global warming as well as protecting human health. Since diesel engines last a long time, we have a lot of sooty engines to clean up.

So let’s act locally in encouraging leaders to support strong federal and state initiatives to curtail black carbon emissions along with CO2 because it has global implications. We are ready to lead the Southeast in pushing for federal and local policies to ensure immediate clean up of diesel emissions.

Please join the Georgia and North Carolina Clean Diesel Campaigns and email list by contacting Laura and continue to follow updates on this issue here as well.

Check out our video from the Atlanta School Bus Air Quality and Retrofit Demonstration.

Check out additional videos from the National Partnership to Reduce Diesel Pollution,

Stephen Smith
Dr. Stephen A. Smith has 30 years of experience effecting change for the environment. Since 1993, Dr. Smith has led the Southern Alliance for Clean Energy (SACE) as its executive…
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