Global Warming Makes It Rain More, Except Where It Makes it Drier

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The news from a new study on the earth's rainfall isn't the fact that global warming is making it rain more in wet areas and less in dry ones, it's how much scientists had previously underestimated that trend: By half.

The finding, published in the latest issue of Science but available without a subscription in Scientific American, means global warming's impact on the earth's water cycle is a lot more pronounced than we'd thought. In short, as research leader Paul Durack, of Lawrence Livermore National Laboratory, told Science, "wet regions will get wetter and dry regions drier."

The new study used a system of 3,500 buoys, called Argo, that sit under the ocean's surface instead of on top, and measure salinity. In regions where more evaporation takes place, the sea becomes saltier. In regions where more rain falls, it's less so. This kind of thing has been hard to measure in the past because weather made it impossible for sensor buoys to take good readings, but the underwater buoys solved that problem, Scientific American reported. And the result was a new understanding of how excess carbon speeds up the earth's water cycle:

Though various computer models match the actual distribution of saltier and fresher regions quite well, the computer models underestimated the actual rate of water cycle intensification by half. That suggests that impacts on the water cycle of future warming of several degrees Celsius will be substantial, strengthening rainfall and evaporation by as much as 24 percent.

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