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Sunlight Sponge? Energy trackers gauge water vapor's wild dance

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12:21pm, August 7, 2002

Despite decades of study, climate-change researchers still can't tell what in Earth's atmosphere is responsible for up to 30 percent of the solar radiation soaked up there. Some scientists argue that water vapor–the atmosphere's major sunlight absorber–takes in much more solar radiation than has been indicated by measurements and models.

Vapor doesn't absorb enough radiation to explain the discrepancy fully, suggests a newly reported experiment from the École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland.

Andrea Callegari and his colleagues made unprecedented measurements of a property of vigorously vibrating water molecules. That property, the extent of the molecules' charge separation, is closely related to the amount of light energy those agitated molecules can absorb. Charge becomes separated in water molecules because oxygen and hydrogen atoms don't share electrons equally.

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