Energy Secretary Steven Chu warned that, if climate change continues unabated, California's agriculture could vanish by the end of the century.

Speaking with the Los Angeles Times, Mr. Chu, a Nobel Prize-winning physicist who ran the Lawrence Berkeley National Laboratory before joining the Obama administration, said that warming temperatures could eliminate up to 90 percent of the Sierra snowpack, which provides water to many of the state's 76,000 farms.

"I don't think the American public has gripped in its gut what could happen," he told the newspaper. "We're looking at a scenario where there's no more agriculture in California."

"I don't actually see how they can keep their cities going," he added.

According to statistics from the US Department of Agriculture [PDF], California is responsible for about half of US fruit, nut, and fresh vegetable production.

As the LA Times notes, Chu is not a climate scientist. His Nobel Prize, which he shared with French physicist Claude Cohen-Tannoudji and American physicist William Daniel Phillips, was awarded in 1997 for his contributions to “laser cooling,” a method of trapping gaseous atoms with laser light.

Chu's warning – that Sierra snowpack could dip by 90 percent by century's end – is far more dire than others have predicted. A report last year written by University of California, Berkeley, researchers Fredrich Kahrl and David Roland-Holst said that snowpack on the mountain range is "projected to shrink by 30 percent by 2070-2099." The report adds that "[d]rier higher warming scenarios" put that figure at 80 percent.

[Update: Commenter Daniel Zappala has pointed to a February 2006 report [PDF] from the California Climate Change Center that says that a 90 percent reduction in snowpack is plausible under a worst-case scenario. See Mr. Zappala's comment below.]

Still, as The Monitor's Pete Spotts pointed out in his Horizons blog, as California enters its third year of drought, the water content of snowpack on the Sierras and elsewhere in the state sits at 61 percent of normal (as Mr. Spotts explains, measurement of water content is different from measurement of the snowpack itself).

Mr. Spotts quotes Lester Snow, the Director of California’s Department of Water Resources, who warns, “We may be at the start of the worst California drought in modern history,”

(To the great disappointment of this blogger, Mr. Snow doesn't let people call him "Les.")

The decline in spring runoff from the mountains is often cited as contributing to the state's wildfires.

Chu told the LA Times that he hopes that, in addition to mandatory caps on greenhouse gas emissions and billions in funding for alternative energy, public education will play a role in helping to curb global warming.

"I'm hoping that the American people will wake up," he told the Times.