The last three years of drought in California were the worst that the state has experienced in 1,200 years, a study published Thursday by Geophysical Research Letters has found.

also discovered that 2014 was drier than any other continuous span of moisture-deficit years.

What’s more, the report concluded that as human-made climate change continues to worsen, similar kinds of “hot” droughts are more likely to recur in the future. And because California is the world’s eighth-largest economy, significant shortages in its surface water supply have implications far beyond its borders, the report states.

Daniel Griffin, a co-author of the study and NOAA Climate & Global Change Fellow, told the San Jose Mercury News, “We were really surprised. We didn’t expect this.”

The study analyzed tree ring samples from blue oaks in the southern and central parts of the state, as those trees are particularly sensitive to moisture fluctuations and are able to “thrive in some of California’s driest environments,” Griffin said. In addition, the scientists reconstructed rainfall back to the 13th century.

According to the findings,there has never been a three-year period in California during which the temperatures have been as high—and rainfall as low—as they were between 2012 and 2014.