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Water confirmed as major greenhouse gas

The distribution of atmospheric water vapour

Warm and wet: The distribution of atmospheric water vapour, a significant greenhouse gas, varies across the globe. During mid 2005, this image shows that most collected at tropical latitudes, particularly over south Asia, where monsoon thunderstorms swept it high above the land.

Credit: NASA

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"That number may not sound like much, but add up all of that energy over the entire Earth surface and you find that water vapour is trapping a lot of energy," Dessler said.

"We now think the water vapour feedback is extraordinarily strong, capable of doubling the warming due to carbon dioxide alone."

Because the new precise observations agree with existing models of the impact of water vapour, researchers are more confident than ever in their ability to accurately predict how the greenhouse gas will contribute to a temperature rise of a few degrees by the end of the century.

"This study confirms that what was predicted by the models is really happening in the atmosphere," said Eric Fetzer, an atmospheric scientist involved with the Aqua satellite at NASA's Jet Propulsion Laboratory in Pasadena, California.

"Water vapour is the big player in the atmosphere as far as climate is concerned," he said.

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