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THE link between greenhouse gases and global warming has been measured
directly for the first time. John Harries and his colleagues at Imperial
College, London, looked at satellite data showing the Earth’s infrared spectrum
in 1970 and in 1997 (Nature, vol 410, p 355). They say that differences
in the amount of heat reflected from the planet can only be explained by
greenhouse gases—specifically carbon dioxide, methane, ozone, and CFCs.
“Before, the only thing that showed the connection was models,” says Harries.
“This is a real observation.” Surprisingly, the change caused by methane was 30
per cent greater…