Earth

Less of a drag for satellites

29 November 2006

Global warming may help satellites stay in low Earth orbit for longer, but at some cost to their solar panels.

Jan Lastovi

cka at the Institute of Atmospheric Physics in Prague, Czech Republic, and colleagues say evidence is mounting that the upper atmosphere is cooling and shrinking as greenhouse-gas levels rise (Science, vol 314, p 1253).

Heat from the Earth’s surface is absorbed by atmospheric carbon dioxide and emitted as infrared radiation. In the denser lower atmosphere the CO₂ absorbs it and radiates it back to Earth, but higher up it is lost into space.

Cooling shrinks the…