Haze clears on sooty climate conditions

The results of a new study by U.S. and Chinese scientists suggest that soot plays

CLEAR PROBLEM. Haze surrounds a small Chinese factory that belches soot. R. Greenwald and J. Xu

a bigger role in regional climate changes than scientists had previously realized. People in developing countries often produce the microscopic carbon particles by inefficiently burning diesel fuel, coal, and plant matter.

The study suggests that increases in atmospheric soot during the past few decades have contributed to severe rains in southern China and droughts and dust storms in the northern region (SN: 10/6/01, p. 218: Ill Winds).

Researchers from NASA’s Goddard Institute for Space Studies in New York, Columbia University, and the National Science Foundation of China in Beijing ran computerized climate models with and without soot. The model with soot reproduced actual precipitation changes in China and regional cooling in China and India. The scientists report their findings in the Sept. 27 Science.

Soot particles heat the atmosphere by absorbing sunlight but can cool locally by blocking sunlight from reaching the ground.

The results provide another reason, beyond health consequences, to curb soot emissions, says study coauthor James Hansen of NASA’s Goddard Institute for Space Studies in New York.


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