The agriculturally rich state of California is no stranger to droughts, but according to a new study reported by Science Daily, the current two-year drought is the state’s worst in 1,200 years.

“This is California–drought happens,” stated co-author Daniel Griffin, an assistant professor in the Department of Geography, Environment and Society at the University of Minnesota, who wanted to see just how bad the 2012-2014 drought has been in comparison to California’s long history of droughts. He and Kevin Anchukaitis, an assistant scientist at Woods Hole Oceanographic Institution, studied tree-ring samples from California’s blue oak trees, which are sensitive to changes in moisture. “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,” he said.

They attribute the extremity of the drought to high temperatures:

As soon as the National Oceanic and Atmospheric Administration (NOAA) released climate data for the summer of 2014, the two scientists sprang into action. Using their blue oak data, they reconstructed rainfall back to the 13th century. They also calculated the severity of the drought by combining NOAA’s estimates of the Palmer Drought Severity Index (PDSI), an index of soil moisture variability, with the existing North American Drought Atlas, a spatial tree-ring based reconstruction of drought developed by scientists at Columbia University’s Lamont-Doherty Earth Observatory. These resources together provided complementary data on rainfall and soil moisture over the past millennium. Griffin and Anchukaitis found that while the current period of low precipitation is not unusual in California’s history, these rainfall deficits combined with sustained record high temperatures created the current multiyear severe water shortages. “While it is precipitation that sets the rhythm of California drought, temperature weighs in on the pitch,” says Anchukaitis.

California has weathered long periods of scant precipitation — even 100-year megadroughts — but the extreme temperatures have increased the severity of the drought to an “unprecedented” level, concludes Live Science.

And what’s more concerning is that this may become more and more frequent. Anchukaitis attributes the problem to climate change, saying, “there is no doubt that we are entering a new era where human-wrought changes to the climate system will become important for determining the severity of droughts and their consequences for coupled human and natural systems.”

(Photo: John Weiss)