Thursday, November 13, 2008

Giant Asian smog cloud masks warming impact: U.N.

Reuters: A three-kilometer thick cloud of brown soot and other pollutants hanging over Asia is darkening cities, killing thousands and damaging crops but may be holding off the worst effects of global warming, the U.N. said on Thursday. The vast plume of contamination from factories, fires, cars and deforestation contains some particles that reflect sunlight away from the earth, cutting its ability to heat the earth.

"One of the impacts of this atmospheric brown cloud has been to mask the true nature of global warming on our planet," United Nations Environment Program head Achim Steiner said at the launch in Beijing of a new report on the phenomenon.

The amount of sunlight reaching earth through the murk has fallen by up to a quarter in the worst-affected areas and if the brown cloud disperses, global temperatures could rise by up to 2 degrees Celsius.

But the overall effect of slowing climate change is not the silver lining to a dark cloud that it appears to be. The choking soup of pollutants may hold temperatures down overall, but the mix of particles means it is also speeding up warming in some of the most vulnerable areas and exacerbating the most devastating impacts of higher temperatures.

The complex impact of the cloud, which tends to cool areas near the surface of the earth and warm the air higher up, is believed to be causing a shortening of the monsoon season in India while increasing flooding there and in southern China.

…."We used to think of the brown cloud as a regional-scale urban problem, now we know because of fast transport it travels vertically for three to four kilometers and spreads," said Professor Veerabhadran Ramanathan, head of the U.N. scientific panel which is carrying out the research.

Smog in Shanghai, shot by DL5MDA, Wikimedia Commons, under the terms of the GNU Free Documentation License, Version 1.2

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