California's drought looks like the worst in the state in more than 1,200 years, according to a new analysis of tree ring and soil moisture data. The study by Daniel Griffin of the University of Minnesota and Kevin Anchukaitis of Woods Hole Oceanographic Institution finds that three-year droughts like the current one aren't unusual in California. But the past three years have been the worst in 1,200 years, with accumulated moisture deficits the worst ever, they said.
How did they determine that? They collected tree-ring samples from blue oak trees, Woods Hole said in a blog post, then combined data from the Palmer Drought Severity Index and the North American Drought Atlas, which measures drought over the past 2,005 years using tree-ring chronologies. "The current California drought is exceptionally severe in the context of at least the last millennium," says the study, which has been accepted for publication in the journal Geophysical Research Letters.
Other researchers have suspected that the long drought in the U.S. Southwest was the worst in a very long time, possibly even surpassing the megadrought of the 16th century. Recent rain that has pummeled much of the Golden State might help alleviate the drought if it's followed by more such storms — on the order of one every three to five days for the next three months, a state climatologist told NBC News this week.
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