Downside of Cleaner Air: More Warming ; Fewer Pollutants Means Average Temperatures May Rise 8 Degrees F. by 2100, New Research Suggests

Article excerpt

New measurements of tiny particles in Earth's atmosphere contain a sobering message: All those hard-won efforts to cut air pollution may unwittingly accelerate global warming.

The result: The planet is likely to warm more and faster than current projections suggest, according to a team of British and American scientists.

The group has produced the most precise estimates yet of how tiny particles, known as aerosols, could affect the world's climate. Aerosols, which include pollutants, have a cooling effect on the atmosphere, and the team's work suggests that the cooling effect is strong - nearly as strong as the top estimates of the United Nation's Intergovernmental Panel on Climate Change (IPCC).

Thus, the dwindling presence of aerosols means that global average temperatures could rise faster than previously estimated and reach toward the high end of projections for the end of the century.

Those estimates currently range from 2.7 to 7.9 degrees F., depending on how emissions of greenhouse gases and other factors play out in coming years.

The results, published in the current edition of Nature, imply "future atmospheric warming greater than is presently predicted, as aerosol emissions continue to decline," suggests the team, led by Nicolas Bellouin at Britain's Meteorological Office in Exeter.

Aerosols occur naturally as dust blown from deserts, wind- whipped sea salt, and emission from volcanoes. They also come from burning fossil fuels. But scientists have had a tough time discerning aerosols' precise role in affecting climate.

The IPCC has been trying to get a clear picture of aerosols' impact for at least 10 years, "but the results always come up very uncertain," says James Coakley, an atmospheric scientist at Oregon State University in Corvallis. …


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