brown cloud, air pollution

Asia’s Brown Cloud

A sunlight-choking chemical stew hangs over Asia and blocks the sun. Will the next brown cloud appear over your city?

By Leah Zerbe


Asia’s Brown Cloud

The future is murky, unless we act to clear the air.

RODALE NEWS, EMMAUS, PA—A nearly 2-mile-thick brown cloud filled with man-made particles and carcinogenic soot from coal-fired power plants and wood-burning stoves has been blocking Asian cities’ sunlight for years, according to a United Nations Environment Programme report released recently. The man-made brown cloud/greenhouse gas combo is melting Kindu Kush-Himalayan-Tibetan glaciers, shifting rain patterns, and stirring up more-intense storms that often lead to flooding, according to the report.

THE DETAILS: The report describes atmospheric brown clouds, or ABCs, over Asian megacities, such as Bangkok, Beijing, Cairo, Lagos, and New Delhi, among others. Some of those cities have experienced a 20% reduction in sunlight since the 1970s. Closer to home, the Amazon Basin in South America is also considered a brown-cloud hot spot. The clouds sometimes form over the eastern United States and Europe, though they’re not as soot-filled as the others, and don’t stick around all year (at least not yet).

ABCs spell trouble for glaciers and snowpacks that supply water to Asia’s major river systems: While they can cool areas on the surface, they amplify greenhouse warming at higher elevations, forcing faster melting. If the glaciers continue to retreat at the current pace, they will shrink by 75% by midcentury, creating a huge drop in the region’s water supply. The clouds could wreak havoc on farming, too: Because of all the pollution, ozone levels at ground level increase, damaging crops. The brown clouds cause dimmer skies and could stall photosynthesis, and their pollutant particles can cause harmful chemical deposits on plants. In addition, toxic concoctions inside these clouds have been linked to respiratory disease and cardiovascular problems. Researchers estimate that 337,000 deaths per year in India and China can be linked to these toxin-rich air-pollution plumes.

WHAT IT MEANS: Burning filthy rocks for energy is also polluting the air we breathe and warming the planet to dangerous levels. The brown clouds that result are threatening agricultural systems and making people sick.

Here are four ways you can make a difference:

Published on: December 17, 2008
Updated on: May 13, 2010


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