Decades of drought in Africa caused by pollutants emitted by U.S. and Europe (Onearth)

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http://www.onearth.org/blog/how-the-us-clean-air-act-brought-the-rains-down-in-africa

How the U.S. Clean Air Act Brought the Rains Down in Africa

BY JASON BITTEL

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In a paper published Friday in the journal Geophysical Research Letters, a team of researchers from the University of Washington shows that decades of drought in Africa were caused, at least in part, by pollutants emitted by the United States and Europe. Throughout the 60s, 70s, and 80s, coal-burning factories spewed sulfate-laden aerosols into the atmosphere with reckless abandon. These tiny particles — which volcanoes can also emit naturally — reflect sunlight and produce more reflective, longer-lasting clouds. The increased cloud cover caused temperatures to drop across the Northern Hemisphere, which in turn, caused rain patterns to shift away from certain areas of Africa. These shifts, the researchers argue, contributed to droughts that choked central Africa and resulted in 100,000 deaths between the 60s and 80s.

Meanwhile, with the intention of improving air quality at home, the U.S. and Europe began to restrict coal pollution in 1970 with the Clean Air Act and other legislation. It’s only now, after decades worth of precipitation observations, that researchers have been able to tie the end of the African drought to western legislation. As our factories scaled back production of sulfate aerosols, the pollution’s cooling effect slowly reversed and rainfall in Africa returned to historic levels by the mid-1980s.

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