"Our results indicate that intact tropical forests are taking up a large amount of carbon," Stephens explains. "They are helping to offset industrial carbon emissions and the atmospheric impacts of clearing land more than we realized."

Most of the computers models produced incorrect estimates because, in relying on ground-level measurements, they had failed to accurately simulate the movement of carbon dioxide vertically in the atmosphere.

The computer models tended to move too much carbon dioxide down toward ground level in the summer, when growing trees and other plants take in the gas, and not enough carbon dioxide up from ground level in the winter.

As a result, scientists believed that there was less carbon in the air above mid-latitude and upper-latitude forests, presumably because trees and other plants were absorbing high amounts.

Conversely, scientists had assumed a large amount of carbon was coming out of the tropics and moving through the atmosphere to be taken up in other regions.

The new analysis of aircraft samples shows that this is not the case.

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Contact: Cheryl Dybas
cdybas@nsf.gov
703-292-7734
National Science Foundation
21-Jun-2007