Researchers Say California Drought is Worst Drought in 1,200 Years

Posted on December 9, 2014

California US Drought Monitor Map for Dec 2 2014

Much of California is currently in a terrible drought. Over half the country is in what is categorized by the United States Drought Monitor has exceptional drought. Nearly 80% of California is in extreme drought.

The image above shows the U.S. Drought Monitor map for December 2, 2014 for the state of California. The map can be found here. Climate scientists from the University of Minnesota and Woods Hole Oceanographic Institution say the California drought from 2012 to 2014 is the worst drought in the region in 1,200 years.

The researchers collected new tree-ring samples from blue oak trees in southern and central California. Using their blue oak data, they reconstructed rainfall back to the 13th century. Other data sources used included the Palmer Drought Severity Index (PDSI), an index of soil moisture variability, and the North American Drought Atlas, a spatial tree-ring based reconstruction of drought developed by scientists at Columbia University's Lamont-Doherty Earth Observatory.

Daniel Griffin, an assistant professor in the Department of Geography, Environment and Society at the University of Minnesota and NOAA Climate & Global Change Fellow, explained in a statement about why blue oak were chosen. He says, "California's old blue oaks are as close to nature's rain gauges as we get. They thrive in some of California's driest environments."

Griffin and Anchukaitis, Kevin Anchukaitis, an assistant scientist at Woods Hole Oceanographic Institution, discovered that the current period of low precipitation is not unusual in California's history. However, the record heat combined with this low precipitation is unusual. The researchers found that the low rainfall deficits combined with sustained record high temperatures created the current multiyear severe water shortages that California is currently experiencing.

Griffin also says he and Anchukaitis were surprised at their findings. Griffin says, "We were genuinely surprised at the result. This is California--drought happens. Time and again, the most common result in tree-ring studies is that drought episodes in the past were more extreme than those of more recent eras. This time, however, the result was different."

The results of the study were published in Geophysical Research Letters in an article called, "How unusual is the 2012-2014 California Drought?"

Photo: United States Drought Monitor
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