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Report links California drought, climate change

"This isn't a projection of 100 years in the future," Noah Diffenaugh said. "This is an event that is more extreme than any in the observed record."

By Brooks Hays
People look over remains of the old Gold Rush settlement of Mormon Island which has resurfaced due to the historic low water levels of Folsom Lake, in Folsom, California, on January 19, 2014. California Governor Jerry Brown declared a state wide drought last Friday. UPI/Ken James
People look over remains of the old Gold Rush settlement of Mormon Island which has resurfaced due to the historic low water levels of Folsom Lake, in Folsom, California, on January 19, 2014. California Governor Jerry Brown declared a state wide drought last Friday. UPI/Ken James | License Photo

STANFORD, Calif., Sept. 29 (UPI) -- The unprecedented and ongoing drought that has stifled California's shrinking reservoirs and parched farmlands for almost two years now is likely influenced by manmade climate change.

At least that's the conclusion of climate scientists at Stanford University who published a study in the journal Bulletin of the American Meteorological Society, this week, suggesting prolonged drought conditions are more likely when the atmosphere is polluted with an excess of greenhouse gases.

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The researcher, led by Stanford climate scientist Noah Diffenbaugh, used a series of computer models to show that drought conditions were more likely to occur when the atmosphere hosts even a moderate amount of greenhouse gases -- as opposed to none at all.

"Our research finds that extreme atmospheric high pressure in this region -- which is strongly linked to unusually low precipitation in California -- is much more likely to occur today than prior to the human emission of greenhouse gases that began during the Industrial Revolution in the 1800s," Diffenbaugh said in a press release.

Diffenbaugh and his colleagues acknowledge that the direct cause of California's lengthy drough is the presence large region of high atmospheric pressure in the northeastern Pacific. This so-called "blocking ridge" -- in this instance, commonly referred to as the Ridiculously Resilient Ridge, or "Triple R" -- has prevented winter storms from reaching California and relieving drought symptoms.

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But as Diffenbaugh's new research shows, the Triple R phenomenon is more likely under conditions featuring moderate to high greenhouse gas concentrations.

"We've demonstrated with high statistical confidence that the large-scale atmospheric conditions, similar to those associated with the Triple R, are far more likely to occur now than in the climate before we emitted large amounts of greenhouse gases," said Bala Rajaratnam, a Stanford statistician.

"This isn't a projection of 100 years in the future," Diffenaugh added. "This is an event that is more extreme than any in the observed record, and our research suggests that global warming is playing a role right now."

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