California Drought Not Due to Human-Caused Climate Change, NOAA Report States

California Drought Not Due to Human-Caused Climate Change, NOAA Report States

The devastating 3-year drought, which began in 2011 and is ongoing despite recent rains, was caused by a high pressure system that was sitting over the West Coast and part of the North Pacific Ocean, driving moisture away from California, report co-author Richard Seager, a professor of oceanography at the Columbia University Lamont-Doherty Earth Observatory in Palisades, N.Y., said.
The persistence of the high pressure ridge was also present in previous long-term droughts in California, some of which were longer than the current drought. The ridge was initially caused by cool sea surface temperatures in the Pacific brought about by a La Niña in 2011, but it persisted even after cool ocean surface temperatures began to warm, the study says.
“Two-thirds of the precipitation deficit in California were due to factors we wouldn’t judge to have long predictability at all,” report co-author Martin Hoerling, a NOAA research meteorologist in Boulder, Colo., said. “They resulted from the randomness of the atmosphere.”
Despite the extreme drought, winter precipitation in California has followed no particular trend since 1895 and is expected to increase because a low pressure system is expected to park itself over the North Pacific each winter, driving moisture into the state, Hoerling said.
Even though the drought may not have been caused by climate change, the drought’s effects may be worse because of hotter temperatures on land that may be caused by global warming, the study says.

 http://www.weather.com/science/environment/news/california-drought-climate-change-noaa