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| Eliminating soot could slow global warming By Reuters Wednesday, December 12, 2001 SAN FRANCISCO � Greenhouse gases are blamed by many scientists for contributing to global warming, but at least one researcher says the real key to modifying world temperatures is diesel soot. "If you want to control global warming, the first thing to go after is soot,'' Mark Jacobson, an associate professor of civil and environmental engineering at Stanford University, said Tuesday. Jacobson, in a presentation to the American Geophysical Union, said soot produced by burning diesel fuels, coal, and wood has a much more severe impact on the environment relative to its mass than do greenhouse gases such as carbon dioxide and methane. Eliminating all fossil-fuel soot � estimated at about 5 million tons per year worldwide � could cut net global warming by 40 percent in three to five years, Jacobson said. "Controlling fossil-fuel soot will not only slow global warming but also will improve human health,'' he said. A soot particle, made up primarily of black carbon, warms the air by absorbing sunlight and radiating the heat into the air. Greenhouse gases, by contrast, do not absorb sunlight but create warming by absorbing Earth's heat and then radiating it back into the environment. Jacobson said that while soot was widely believed to be the biggest cause of global warming after carbon dioxide, controlling soot emissions could have a more immediate effect on temperatures because soot does its damage to the environment during the relatively brief time it remains in the air. But he said that most current climate change models do not take soot into account. The 1997 Kyoto Protocol, aimed at reducing global warming, also failed to deal with soot emissions, he noted. Jacobson, who reached his conclusions after developing a computer model to include the climactic impact of soot, said controls could be improved by tightening standards on particulate emissions, requiring industry to devise better particle traps, and switching from diesel fuel to gasoline or hydrogen fuel cells. Diesel fuel powers almost all commercial trucks, buses, and tractors worldwide and 33 percent of the passenger vehicles sold in Europe last year, according to Jacobson. Diesel-powered passenger vehicles are much rarer in the United States � only about one in a thousand cars � but overall diesel emissions from all vehicles in the United States are still about 75 percent to 80 percent of those of Europe. Copyright 2001 � Reuters Any reprinting, rebroadcast or digital transmission of this work without written permission from Environmental News Network, Inc. is strictly prohibited. |
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