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68WWW.CEN-ONLINE.ORG SEPTEMBER 22, 2008
GOVERNMENT & POLICY
A NEW FEDERAL REPORT is suggesting a novel policy to forestall climate change in the short run. Rather than making deep cuts in carbon dioxide emissions, it says policymakers should consider slashing certain types of air pollutants, such as black carbon and smog, in the next decade or so.
This strategy would buy time for development of new energy technologies that sharply curb or eliminate CO2 emis-sions, according to the report, “Climate Projections Based on Emissions Scenarios for Long-Lived and Short-Lived Radia-tively Active Gases and Aerosols.” Re-leased in early September by the U.S.
Climate Change Science Program, the report also points out that the cuts in pol-lution would provide health benefits to people.
The report shows that regional air pollution controls need to be integrated into global climate-change policy, says Drew T. Shindell, coauthor of the report and a climate scientist at the National Aeronautics & Space Administra-tion’s Goddard Institute for Space Studies. Changes in air pollution levels are projected to contribute 20% of human-caused global warming by 2050, according to report coauthor Hiram (Chip) Levy II, senior re-search scientist at the National Oceanic & Atmo-spheric Adminis-tration’s Geophysi-cal Fluid Dynamics Laboratory.
Reducing emissions from wood, dung, and other biomass burned for cooking and heating homes in Asia appears to offer the biggest bang for the buck as a short-term policy to offset global warming, the report says. Cuts in smog-forming pollution from cars and trucks in North America could have a similar impact, it adds.
THESE POLICIES would curb two types of widespread air pollutants that absorb Earth’s heat, contributing to global warm-ing. One is black carbon, a type of tiny soot particle released during combustion, especially the burning of biomass and die-sel. The other is ground-level ozone, com-monly called smog, which is formed from vehicle tailpipe emissions and releases of
volatile organic compounds. Both smog and fine particles cause health problems and are targets of current air pollution regulations.
In contrast to smog and black carbon, some air pollutants actually counteract global warming, the report points out. For instance, sulfate particles that are by-products of burning coal reflect the sun’s energy into space and thus help cool the planet. Sulfates also stimulate the for-mation of clouds, which reflect light and contribute to cooling. Therefore, regula-tions to control emissions from coal-fired power plants may contribute to global warming because they lower the level of sulfates in the atmosphere, the report says.
Anticipated increases in levels of black
carbon and smog and a decrease in sulfate emissions are projected to cause a temper-ature rise of 3 ºC in the middle of the U.S. and in the eastern Mediterranean by 2100, the report says.
Although the report recommends tar-geted air pollution controls in the short term, these controls are not a substitute for addressing CO2 emissions, Shindell says.
Allen Robinson, a professor of mechani-cal engineering at Carnegie Mellon Univer-sity, tells C&EN that curbing particulate matter emissions in Asia would amount to a “finger in the dike” in dealing with cli-mate change.
The report is available at climatescience . gov/Library/sap/sap3-2/final-report/ #finalreport.—CHERYL HOGUE
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THE HEAT IS ON Short-lived air pollutants could cause temperature rises of 3 ºC in the U.S. heartland and eastern Mediterranean region by 2100, according to a new federal report.
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