From the department of global warming

The Bay Area is taking a break from global warming:

California is bracing for a severe cold snap that could see snow at sea level and may threaten $840 million worth of the state’s citrus crops. Local government agencies are preparing for the unusually frigid spell by opening “warming centers” for those without heat and patrolling overnight for homeless people who are at risk of hypothermia.

“The temperatures they’re projecting are pretty unusual,” said Trent Rhorer, director of the San Francisco Department of Human Services. “Maybe three times a year we’ll activate a cold weather system for our homeless shelters, but this looks like it’s going to be extraordinarily cold. We’re stepping up more than we usually do.”

The Bay Area typically gets a few cold spells every winter, but it’s unusual for the temperature to drop below the 30s, and almost unheard of for it to stay in the 20s for more than a couple of hours.

After an unseasonable warm spell last week, temperatures have been slowly dropping as a cold-air mass swoops down from Canada, said Jan Null, an adjunct professor of meteorology at San Francisco State University and a retired lead forecaster with the National Weather Service. Typically, winter storms move west to east through California, bringing with them warm, wet air from the Pacific, Null said. It’s very unusual to get a cold front straight from the north.

The last time we had this kind of cold snap here was in February 1991.

Certainly the cold snap is not a refutation of global warming (although I continue to be averse to Al Gore’s hysterical scenario), but it is a reminder that weather is unreliable and cyclical.