Tuesday, September 30, 2014

California drought and climate warming: Studies find no clear link

Global warming contributed to extreme heat waves in many parts of the world last year, but cannot be definitively linked to the California drought, according to a report released Monday. The third annual analysis of extreme weather events underscored the continuing difficulty of teasing out the influence of human-caused climate change on precipitation patterns. One of three studies examining the California drought in 2013 found that the kind of high-pressure systems that blocked winter storms last year have increased with global warming. But another study concluded that a long-term rise in sea surface temperatures in the western Pacific did not contribute substantially to the drought. And researchers noted that California precipitation since 1895 has "exhibited no appreciable downward trend." Overall, the report editors concluded that the papers didn't demonstrate that global warming clearly influenced the drought, which is one of the worst in the state record.  In the report, published in the Bulletin of the American Meteorological Society, 20 research teams explored the causes of 16 extreme weather events recorded in 2013, including torrential downpours in Colorado, heat waves in Korea and Australia and a blizzard in South Dakota. The studies overwhelmingly showed that human-caused climate change played a role in the heat waves, in some cases making them 10 times more likely. But the report editors wrote that "natural variability likely played a much larger role in the extreme precipitation events," whether it was flooding in India, deep snow in the Spanish Pyrenees Mountains or the California drought...more

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