Can Someone Point to the Science?

Energy Secretary Steven Chu, about whom I’ve heard nothing but good things, was quoted as follows in the L.A. Times:

Reporting from Washington — California’s farms and vineyards could vanish by the end of the century, and its major cities could be in jeopardy, if Americans do not act to slow the advance of global warming, Secretary of Energy Steven Chu said Tuesday. . .

In a worst case, Chu said, up to 90% of the Sierra snowpack could disappear, all but eliminating a natural storage system for water vital to agriculture.

“I don’t think the American public has gripped in its gut what could happen,” he said. “We’re looking at a scenario where there’s no more agriculture in California.” And, he added, “I don’t actually see how they can keep their cities going” either.

Can someone point me to a study suggesting that there will be no more agriculture or cities in California by 2100? What does the IPCC say? What is the consensus view?

After 8 years of the Bush Administration’s cherry picking and selective reading of climate science it would be a shame to see the Obama Administration do exactly the same thing.