Aerosols Create Cooling Effect

Scientists have long suspected that aerosols in the atmosphere interact with clouds to influence the climate, but they weren't sure why.

Now, scientists used NASA satellite data to observe the interaction of clouds and aerosols over the Atlantic Ocean between June and August 2004 and found that by increasing cloudiness and reflecting solar energy, aerosols provided a net cooling influence on the region during the three-month period.

This image shows the net effect of aerosols on the amount of energy that the Earth's atmosphere reflected back to space during the study. The brightest pink spots to the west of Africa's Sahara Desert and off the coast of Southern Africa represent the largest increases in reflection.

The types of aerosols the scientists encountered in shallow clouds at an average height of 1,200 meters varied widely with latitude. Between 30 and 60 degrees North they found urban pollution; dust from the Sahara between 5 and 25 degrees North; smoke from seasonal fires in Africa between 5 degrees North and 20 degrees South; and salts from wind-whipped sea spray between 20 and 30 degrees South. However, despite these differences, the effects were the same.

These findings were recently detailed in the journal Proceedings of the National Academy of Sciences.

--Bjorn Carey

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Credit: NASA Earth Observatory