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Last Friday, Californians woke up to this cheery news on their climate front:

"State officials reported a Sierra Nevada snowpack smaller than normal on Thursday and said California may be at the beginning of its worst drought in modern history. Residents were immediately urged to conserve water."

Okay, I realize this sounds bad enough, but I always have a problem when state water officials in the West compare their droughts to previous ones in "modern history," which usually means the last hundred years or so. We really need to extend the timescale a bit--say by 1,000 years--if we want to grapple with drought as a cyclical weather phenomena. Advances in tree ring science have revealed that numerous mega-droughts (lasting decades) hammered the West and Midwest 750 years ago. Then factor in those pesky greenhouse gases, and the future of the American West looks like this, according to a 2007 Columbia ...