California is currently experiencing one of the most severe droughts on record, but it is nothing compared to North America's worst drought of the last 1,000 years.

That distinction belongs to the drought of 1934, which was the driest and most widespread of the millennium, a new NASA study found. During that year, the American plains were transformed into the Dust Bowl, whose barren crop fields devastated farmers throughout most of the 1930s.

Scientists from NASA and Lamont-Doherty Earth Observatory used a tree-ring-based drought record from the years 1000 to 2005 and modern records in their analysis published in the journal Geophysical Research Letters. They found that the drought in 1934 was 30 percent worse than the next severe drought in 1580. The 1934 drought covered 71.6 percent of western North America. The 2012 drought, which was the worst drought in more than half a century, had an average coverage of 59.7 percent.

The 1934 drought was caused by a high-pressure system in winter in the West Coast that did not allow wet weather and the dust storms in the spring of 1934 had stopped rain from falling. Poor land management on the part of humans were actually responsible for that latter cause.

"In combination then, these two different phenomena managed to bring almost the entire nation into a drought at that time," said the study's co-author Richard Seager in a statement. "The fact that it was the worst of the millennium was probably in part because of the human role."

The reason why dust clouds can be so problematic is because they reflect sunlight and block solar energy from reaching the earth. That means there's no evaporation, which helps form rain clouds.

However, the dust storms of the 1930s are a thing of the past. Today, the agricultural practices are different, and they minimize erosion. Scientists have linked the current drought in California to climate change. A study released in September found that high atmospheric pressure over the Pacific Ocean that kept storms away was much more likely to form when greenhouse gases were present.

Climate change can worsen droughts in North America, a recent Fifth Assessment Report of the Intergovernmental Panel on Climate Change found. Looking back at droughts that occurred 1,000 years ago may help scientists better understand how climate change will impact the droughts of the present and the future. At the rate climate change is impacting our planet, we better hope we can figure out ways to better deal with the effects of droughts — and fast.

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