for National Geographic News
Pollution in Asia is altering global weather patterns by creating larger clouds and more intense storms, a new study says.
The findings are the first definitive link between human activities and significant shifts in storm patterns that influence weather worldwide, the researchers write.
The affected weather system, known as the Pacific storm track, spins off tropical cyclones and typhoons, the authors point out. (Related photo: 'Supertyphoon' Batters China Coast [August 11, 2006].)
Even more significantly, the storms affect global air and heat circulation and may be linked to warming in the polar regions. (Related: "Arctic Summers Ice Free by 2040, Study Predicts" [December 12, 2006].)
"The intensified Pacific storm track likely has profound implications on climate," said lead researcher Renyi Zhang, an atmospheric scientist at Texas A&M University.
The research is presented in this week's online edition of the journal Proceedings of the National Academy of Sciences.
Previous research has found that smoke from wildfires in the Amazon rain forest delays the onset of storms in the region. When the storms do arrive, they're fiercer.
And urban pollution has been blamed for intensified electricity and lightning in storms over cities.
So Zhang and his colleagues turned an eye to Asia, where rapid industrialization and population growth over the past two decades have spurred huge increases in pollution from the burning of fossil fuels.
The team studied the region's average cloudiness during the past 20 years, focusing on deep convective clouds, which start close to Earth and can tower about six miles (ten kilometers) or higher. Such clouds are associated with intense storm activity, such as the eye-walls of cyclones.
The researchers found that the clouds increased in frequency by 20 to 50 percent over that time frame, corresponding to an observed increase in soot, sulfur dioxide, and other aerosols from coal and oil burning.
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