The Dust Bowl is not just the worst drought that occurred in North America over the past 100 years. Researchers have found evidence that it is also the worst of the past millennium.

The 1930s was marked by a series of drought that caused severe devastation with farms yielding damaged crops and livestock dying because of the hot temperature, deficient rainfall, dust storms and erosion.

Dust Bowl had such impact on agriculture it is believed to have played a role in exacerbating the Great Depression and a study published in the Geophysical Research Letters on Sept. 23 highlights just how dry and widespread this period of drought was.

For the study, researchers from the National Aeronautics and Space Administration (NASA) and Lamont-Doherty Earth Observatory looked at tree ring records between the years 1000 A.D and 2005 as well as contemporary weather records to examine some of the exceptional droughts that occurred in the history of North America.

They found that the 1934 wave is the worst drought that hit the continent during the period.

"During the summer of 1934, over 70% of Western North America experienced extreme drought, placing this summer far outside the normal range of drought variability and making 1934 the single worst drought year of the last millennium," the researchers wrote.

The 1934 drought is nearly 30 percent worse than the next most severe drought event that occurred in 1580 with the extremely dry conditions affecting more than 71.6 percent of North America. In comparison, the extent of the 2012 drought was only 59.7 percent.

A high-pressure weather system over the west coast of the U.S. in the winter is known to have contributed to the abnormal rainfall patterns that marked the severe drought but the researchers noted that human activities have exacerbated the condition with poor land management practices that caused the dust storms.

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

The researchers said that although dust storms are no longer a problem in North America, they still warned that agricultural producers should not to forget the lesson of the past, to pay attention to the changes in the climate and adapt accordingly.

"The risk of severe mid-continental droughts is expected to go up over time, not down," Seager said.

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