Friday, June 08, 2007

Earth's Changing Climate

Speedier Satellites
A primary cause of a warmer planet--carbon dioxide emissions--is having effects that reach into space with a bizarre twist. Air in the atmosphere's outermost layer is very thin, but air molecules still create drag that slows down satellites, requiring engineers to periodically boost them back into their proper orbits. But the amount of carbon dioxide up there is increasing. And while carbon dioxide molecules in the lower atmosphere release energy as heat when they collide, thereby warming the air, the sparser molecules in the upper atmosphere collide less frequently and tend to radiate their energy away, cooling the air around them. With more carbon dioxide up there, more cooling occurs, causing the air to settle. So the atmosphere is less dense and creates less drag.