After several winters of little rainfall, California is close to being bone-dry. The third straight year of drought has some of the state's 12 major reservoirs dipping to less than 50 percent of their historic average water levels, and has even raised fears that the state could run out of water.
For Californians, there's been some comfort in the knowledge that the state has endured previous dry periods. But a new study by climate scientists published in Geophysical Research Letters shows that this particular drought's combination of low rainfall and heat is the worst in 1,200 years.
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Daniel Griffin, an assistant professor in the Department of Geography, Environment and Society at the University of Minnesota, and Kevin Anchukaitis, an assistant scientist at Woods Hole Oceanographic Institution, studied tree-ring samples from blue oak trees in the southern and central parts of the state, which allowed them to reconstruct rainfall patterns back to the 14th Century A.D., before Spanish explorers first reached California.
The scientists augmented that with other data gleaned from sources such as the North American Drought Atlas, a spatial tree-ring-based reconstruction of drought developed by scientists at Columbia University's Lamont-Doherty Earth Observatory.
Griffin and Anchukaitis found that while California has often suffered through periods of meager rainfall, record-high temperatures in California have magnified the effects of this one.
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This drought is much more severe than historical droughts that spanned decades, which the scientists believe were punctuated by wet years that partly mitigated their effects.
The study adds evidence to the argument that California's drought is linked to human-induced climate change. Though some scientists have disputed the connection, Stanford University researchers in September published a study showing that persistent high atmospheric pressure hovering over the Pacific - more likely to occur due to greenhouse gas concentrations from burning of fossil fuels - diverted storms away from the California coast at a greater rate, resulting in drought.