Send in the clouds.

Send in the clouds

Clouds are the main middlemen between the sun and earth; more than anything else, they determine how much solar energy reaches the planet and how much of it is reflected back into space. However, scientists have not been entirely clear on the quantitative role clouds play in this radiation budget, and this has been a major hitch in the development of climate models and predictions of the "greenhouse" warming brought on by increases in carbon dioxide and other gases. Some scientists have suggested that increases in cloud cover might cool the atmosphere, offsetting greenhouse warming. But without hard data on clouds' effects on the present-day climate, such suggestions regarding their future effects remain wispy.

For this reason, NASA began its Earth Radiation Budget Experiment (ERBE) in October 1984. According to Experiment Scientist Bruce Barkstrom at Langley Research Center in Hampton, Va., preliminary results, based on a few months' data, indicate that clouds reflect more solar energy than they retain, keeping the atmosphere from absorbing roughly 25 watts per square meter than if they weren't there. This suggests a net cooling effect on the atmosphere. With two satellites up and one to be launched at the end of this month, researchers expect ERBE to provide much more accurate and easily used data for directly assessing the role of clouds than what was available previously.