Brown Clouds Across Asia
A noxious cocktail of soot, smog and toxic chemicals is blotting out the sun, fouling the lungs of millions of people, and altering weather patterns in large parts of Asia.
The byproduct of automobiles, slash-and-burn agriculture, coal-fired power plants, and cooking on dung or wood fires, these plumes rise over southern Africa, the Amazon basin and North America. But they are most pronounced in Asia, where so-called atmospheric brown clouds are dramatically reducing sunlight in many Chinese cities, says Maximilian Auffhammer, assistant professor of agricultural and resource economics and a co-author of a recent UN report on the problem.
In previous studies, Auffhammer and his colleagues found that brown clouds have significantly reduced crop yields in swaths of rural India.
The brownish haze, sometimes in a layer more than a mile thick and clearly visible from airplanes, stretches from the Arabian Peninsula to the Yellow Sea. In the spring, it sweeps past North and South Korea and Japan. Sometimes the cloud drifts as far east as California.
The report identified 13 cities as brown-cloud hot spots, among them Bangkok, Cairo, New Delhi, Tehran and Seoul, South Korea, where the smog blocks from 10 to 25 percent of the sunlight that should be reaching city streets.
For those who breathe the toxic mix, the impact can be deadly. Henning Rodhe, a professor of chemical meteorology at Stockholm University, estimates that 340,000 people in China and India die each year from cardiovascular and respiratory diseases that can be traced to the emissions from coal-burning factories, diesel trucks and wood-burning stoves. “The impacts on health alone is a reason to reduce these brown clouds,” he says.