The Dust Bowl drought of the 1930s caused catastrophic farm and livestock failure throughout the central United States. New research reveals that it was not just the worst dry spell in memory — it was the worst in North America in the past millennium.

The drought of 1934 was so-named for the dust from the Midwest that was blown by winds to as far east as North Carolina and Florida.

“Not only did 1934 [the first year of the Dust Bowl] stand out in terms of extent and intensity, but it was the worst by a fair margin,” says Benjamin Cook, a climate scientist at the NASA Goddard Institute for Space Studies in New York and a co-author of the study.

Cook and his coworkers referenced the North American Drought Atlas, a record derived from tree-ring chronologies that reconstructs precipitation and drought patterns for the past 2,005 years. They discovered that the 1934 drought affected over 70 percent of western North America and was 30 percent worse than the number two drought in the region over the study period, which occurred in 1580.

Earlier work by NASA Goddard Space Flight Center scientists linked the Dust Bowl’s cause to sea-surface temperatures that were a bit cooler in the Pacific compared to the surface temperatures in the Atlantic. Cook and colleagues conclude that these temperatures likely played only a minor role. They say that a high-pressure ridge centered over the North American west coast blocked wet weather from moving eastward during the autumn and winter of 1933–1934.

The report and proposed cause is apropos to the current draught in California, where a similar atmospheric pattern was observed last winter. Cook and his team found that similar high-pressure ridges preceded some of the worst dry spells on the west coast, including the worst California drought in history, the two-year 1976 drought.

The manuscript was published in the most recent issue of the journal Geophysical Research Letters.