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News :: Environment |
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Soot Altering World Climate |
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by Tormy
(No verified email address) |
23 Dec 2003
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December 23, 2003
Washington - Soot mostly from diesel engines is impeding the ability of snow and ice to reflect sunlight, which is contributing to "near worldwide melting of ice" and as much as a quarter of all observed global warming, top NASA scientists say. |
The findings raise new questions about human-caused climate change.
"We suggest that soot is a more all-around 'bad actor' than has been appreciated," NASA scientists James Hansen and Larissa Nazarenko wrote in a paper published yesterday in the Proceedings of the National Academy of Sciences.
Soot comprises carbon particles that are, along with salts and dust, by-products of burning fossil fuels and vegetation. In developed countries, the biggest source is diesel fuel. Elsewhere, burning wood, animal dung, vegetable oil and other biofuels are a major source of soot.
Hansen, director of NASA's Goddard Institute for Space Studies at Columbia University, and Nazarenko, a staff associate there, found soot is twice as potent as carbon dioxide in changing global surface air temperatures in the Arctic and the Northern Hemisphere. Greenland may be an exception, they said, because it is downwind from Canadian forests and has little man-made pollution.
In response to questions from The Associated Press, Hansen said yesterday that the authors estimate the soot effect is equivalent to putting a 1-watt bulb, the size of a miniature Christmas tree bulb, over every two square yards in the Northern Hemisphere. The effect is greater in northernmost snow regions, and about zero in the tropics.
Levels of airborne soot as high as about 100 parts per billion were found in the Alps, enough to reduce the snow's ability to reflect light rather than absorb it from about 98 percent down to between 80 and 90 percent, Hansen said.
Scientists thought until recently that only carbon dioxide and other greenhouse gases have global reach and effect. They now are finding the same thing with these microscopic, suspended particles of pollutants that settle on the ground hours later.
Michael Oppenheimer, a Princeton professor and expert on climate policy, called the study "an interesting early calculation" that could prove to be important.
"It means that - if it's right - we need to keep an eye on it," he said. "When we think about all these greenhouse gases, we ought also to think about controlling these particles that are also changing the climate."
The Bush administration ordered in 2001 pollution cuts from heavy-duty diesel engines and diesel fuel used in highway trucks and buses. This year it proposed requiring a 90 percent reduction in pollution from diesel-powered construction and other off-road equipment starting with 2008 models.
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