Climate Change: Information on Three Air Pollutants' Climate Effects and Emissions Trends (excerpted)

released on May 28, 2003

This is a work of the U.S. government and is not subject to copyright protection in the United States. It may be reproduced and distributed in its entirety without further permission from GAO.

What GAO Found:

Scientists generally agree that sulfate aerosols have a cooling effect
on climate, while ozone in the lower atmosphere has a warming effect.
Black carbon tends to warm the atmosphere but cool the earth’s
surface. Sulfate aerosols also affect how much and where it rains.
Considerable uncertainty remains about the size of these effects.