Tuesday, April 28, 2015

California Drought and Climate Change

As California settles into its fourth year of scant rainfall and record-breaking high temperatures, the state’s snowpack accumulation is record low at 5 percent of the historical average, according to the April 1 measurement when snowpack is normally at its peak, around 28 inches. Snowpack accumulations in 2014 — the state’s hottest and third driest year on record — also stood at, or near record lows, and by June 1, there was virtually no snowpack to replenish state reservoirs. Already in 2015, 93 percent of the state is experiencing drought conditions ranked “severe” or worse — conditions that 100 percent of the state experienced in 2014. The official water allocation dictated by the state’s water management authority for 2015-16 will only meet 20 percent of the water requests from cities and agriculture, and the big reservoirs that provide the bulk of the state’s water remain much lower than normal
Altogether, the drought stands as the worst to hit the state in 1,200 years.
Climate change is linked to California’s drought by two mechanisms: rising temperatures and changing atmospheric patterns conducive to diminishing rains.  The first link is firmly established, and there is a considerable and growing body of evidence supporting the second.
Climate change intensified the California drought by fueling record-breaking temperatures that evaporated critically important snowpack, converted snow to rain, and dried out soils. This past winter in California (December 2014 to February 2015) was officially the warmest on record by a wide margin. February 2015 was California’s singularly warmest February on record. All of this falls on the heels of the 2014 calendar year — which was the warmest in California in 119 years of record keeping, smashing the prior records by an unprecedented margin. 
Weather records tend to be broken when the trend driven by natural changes and the trend driven by climate change run in the same direction, in this case toward warmer temperatures. Drought in California has increased significantly during the past 100 years, driven by rising temperatures.
In addition to fueling hot extremes, there is now considerable evidence that climate change was at least partly responsible for the dramatic fall-off in precipitation during the drought. The unprecedented high-pressure weather pattern known as the “ridiculously resilient ridge” that blocked storms from the state has been linked to climate change by researchers at Stanford University, while other researchers have also identified the fingerprint of global warming in the emergent high-pressure pattern.
http://www.usnews.com/news/blogs/at-the-edge/2015/04/14/climate-change-and-the-california-drought

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