Global warming felt by space junk, satellites

Manmade increases in carbon dioxide might be having effects that are larger than expected

An artist's illustration of the Canadian Space Agency's SCISAT-1 satellite in orbit, which is carrying the Atmospheric Chemistry Experiment to track carbon dioxide levels in Earth's atmosphere.

By Charles Q. Choi

Rising carbon dioxide levels at the edge of space are apparently reducing the pull that Earth's atmosphere has on satellites and space junk, researchers say.

The findings suggest that manmade increases in carbon dioxide might be having effects on the Earth that are larger than expected, scientists added.

In the layers of atmosphere closest to Earth, carbon dioxide is a greenhouse gas, trapping heat from the sun. Rising levels of carbon dioxide due to human activity are leading to global warming of Earth's surface.

However, in the highest reaches of the atmosphere, carbon dioxide can actually have a cooling effect. The main effects of carbon dioxide up there come from its collisions with oxygen atoms. These impacts excite carbon dioxide molecules, making them radiate heat. The density of carbon dioxide is too thin above altitudes of about 30 miles (50 kilometers) for the molecules to recapture this heat, which means it mostly escapes to space, chilling the outermost atmosphere. [ Earth's Atmosphere from Top to Bottom (Infographic) ]

Cooling the upper atmosphere causes it to contract, exerting less drag on satellites. Atmospheric drag can have catastrophic effects on items in space — for instance, greater-than-expected solar activity heated the outer atmosphere, increasing drag on Skylab, the first U.S. space station, causing it to crash back to Earth.

Read the rest here.