California's drought in the big, big picture

  • March 13, 2014

By Allen Best

TAHOE BASIN, Calif. — California has had it rough. Last year less rain fell than in any year since it became a state in 1850. And while snowfall in the Sierra Nevada is usually measured by metres, not centimetres, winter this year got off to such a slow start that not all the ski trails in the Tahoe resorts were opened until last week. Yes, the first week of March.

Guess what? It could get worse. The San Jose Mercury News says researchers have used tree rings, sediment and other natural evidence to document multiple droughts during the last 1,000 years that have lasted 10 or 20 years in a row. That compares with just three years in the current drought.

Among the droughty periods was one that lasted 240 years, and another that lasted 40 years.

"We continue to run California as if the longest drought we are ever going to encounter is about seven years," said Scott Stine a professor of geography and environmental studies at Cal State East Bay. "We're living in a dream world."

A sharper definition to the story is presented by Martin Hoerling, a meteorologist specializing in climate science at the National Ocean and Atmospheric Administration in Boulder, Colo. In a piece published in the New York Times, Hoerling makes several points.

The current drought in California, he says, "resembles the droughts that afflicted the state in 1976 and 1977. Those years were at least as dry as the last two years have been for the state as a whole." And studying records to 1895, he says, no clear trend toward either wetter or drier conditions has been observed.

Hoerling also warns against blaming global warming for this drought. "At present, the scientific evidence does not support an argument that the drought here is appreciably linked to human-induced climate change."

He cites a 2013 report by the International Panel on Climate Change: "Recent long-term droughts in western North American cannot definitely be shown to lie outside the very large envelope of natural precipitation variability in this region, particularly given new evidence of the history of high-magnitude natural drought and pluvial episodes suggested by paleoclimatic reconstructions."

It's natural to wonder about current droughts given the planet's gradual warming due to the rampant burning of fossil fuels, says Hoerling. And it's also notable that demand for water in California has increased dramatically, calling into question the adequacy of the current system of reservoirs and other hydraulic infrastructure in the West in times of drought, whatever the cause.

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