U.S. Southwest's Dry Spell May Intensify with Climate Change

From Scientific American :

By Mike Orcutt  October 29, 2010

A new analysis using a standard drought index augurs that by the end of the century devastating drought conditions will take hold over much of the populated areas of the world


Lake Mead, the massive reservoir created in the late 1930s by Hoover Dam on the Arizona–Nevada border, has dropped to its lowest level ever, it was reported earlier this month. The lake has been steadily growing shallower since drought began reducing the flow of its source, the Colorado River, starting in 2000 due to below-average snowfall in the Rockies.

It is still too early to know whether the situation at Lake Mead and recent droughts throughout the U.S. Southwest are due to anthropogenic global warming, says Aiguo Dai, an atmospheric scientist in the Climate and Global Dynamics Division of the National Center for Atmospheric Research in Boulder, Colo. There is not enough data to rule out natural variability as the fundamental cause. But the decade long dry spell is consistent with the predictions of models used in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) in 2007, which projected that warming of the planet would lead to long-term drying over the subtropics—the climatic regions adjacent to the tropics, ranging between about 20 and 40 degrees north and south latitude, which includes the Southwest.

It's also consistent with a new analysis, authored by Dai, which forecasts that increasing dryness over the next several decades will eventually become devastatingly severe, with long-lasting drought predicted for most of Africa, southern Europe, the Middle East, most of the Americas, Australia, and Southeast Asia.

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And so it goes - one more disaster after another...