The year of 1934 was a dry one, as it boasted the worst drought in North America in the last 1,000 years, a NASA study has found.
During the Dust Bowl days - also known as the Dirty Thirties - the 1934 drought was 30 percent more severe than its runner-up in 1580, and covered 71.6 percent of western North America. The average extent of the 2012 drought, for comparison, was 59.7 percent.
"It was the worst by a large margin, falling pretty far outside the normal range of variability that we see in the record," climate scientist Ben Cook at NASA's Goddard Institute for Space Studies said in a news release.
Two factors in particular set up 1934 for the perfect storm of rainless weather. First, a high-pressure system in winter hovered over the US's West Coast and turned away wet weather. And second, the spring of 1934 saw dust storms, caused by poor land management practices, which also suppressed rainfall by blocking sunlight and prevent evaporation that would otherwise help form rain clouds.
"In combination then, these two different phenomena managed to bring almost the entire nation into a drought at that time," said co-author Richard Seager. "The fact that it was the worst of the millennium was probably in part because of the human role," he added.
Lead study author Cook and his colleagues pegged 1934 as the worst drought in 1,000 years after using a tree-ring-based drought record from the years 1000 to 2005, in combination with modern records.
And since the recent Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) predicted that climate change is likely to only makes droughts in North America worse, researchers believe looking back in time can give them clues as to what we can expect in the future.
"We want to understand droughts of the past to understand to what extent climate change might make it more or less likely that those events occur in the future," Cook said.
Not only are more severe droughts expected in the near future as humans continue to burn fossil fuels and exacerbate climate change, but the southwest United States in particular should brace themselves for megadroughts - droughts that last over 30 years.
The new findings were published in the journal Geophysical Research Letters.