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Friday, December 14, 2007

An Inconvenient Chill: NASA Says Saharan Dust Clouds Cooled The North Atlantic

CINCINNATI (TDB) -- While everyone seemed focused on global warming, two NASA researchers studying the amount of dust in the Earth's atmosphere have found that sea surface temperatures in the North Atlantic cooled. An unexpected big chill took place between between June 2005 and June 2006. NASA reports that satellite photos "provide evidence that the chilling effect of dust was responsible" for much of a temperature drop in the North Atlantic. The dust clouds were blown into the atmosphere from African deserts -- including the vast Sahara -- and reflected sunlight away from the Earth's surface.

The result: Fewer hurricanes than predicted.

Scientists William Lau and Kyu-Myong Kim at the Goddard Space Flight Center in Greenbelt, Md., are publishing data that suggests the dust acted like a sun shade, and the cooling led to fewer hurricanes in 2006, when only five occurred. In 2005, when Katrina struck, there were 15. Many researchers saw climate change as increasing the number of storms and making them more violent. Lau and Kim report that climate patterns are complex, and that heat in one spot can cause a chill in another. Lau said the 2007 hurricane season is another in which forecasts for an above normal number of storms have proven incorrect. The American Geophysical Union's Research Letters distributed some of the data this month. There is a $9 to purchase the entire article online.

While the NASA scientists don't refute global warming, they show there is a lot to learn about climate and atmospheric mechanisms. They calculated that dust caused a 30% to 40% drop in sea surface temperatures between 2005 and 2006 early in the hurricane season. They said dust could be a factor in temperature shifts like El Nino.

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