From the Atlantic Monthly:
"A new study by Cornell University, the University of Arizona, and the U.S. Geological Survey researchers looked at the deep historical record (tree rings, etc.) and the latest climate change models to estimate the likelihood of major droughts in the Southwest over the next century. The results are as soothing as a thick wool sweater on a midsummer desert hike.
The researchers concluded that odds of a decade-long drought are "at least 80 percent." The chances of a "megadrought," one lasting 35 or more years, stands at somewhere between 20 percent and 50 percent, depending on how severe climate change turns out to be. And the prospects for an "unprecedented 50-year megadrought"—one "worse than anything seen during the last 2,000 years"—checks in at a nontrivial 5 to 10 percent."