WASHINGTON, Dec. 15 — MSNBC/AP -- As devastating as the 1930s Dust Bowl was, the Great Plains could see even worse droughts over the next century, according to a government study released Tuesday. Mother Nature might do it on her own, they noted, but land-use patterns and global warming might also contribute.
Using historical documents, tree rings, archaeological remains and plain-old sediments, two National Oceanic and Atmospheric Administration researchers concluded that 20th century droughts -- including the eight-year Dust Bowl -- have been only moderately severe and relatively short compared with "megadroughts" in the 13th and 16th centuries.
"'Two human factors could make the Great Plains even more susceptible to a severe drought in the future. These are land-use practices and global warming," said NOAA scientist Jonathan Overpeck.
Their study, published in December's Bulletin of the American Meteorological Society, also found that a drought like the Dust Bowl can be expected to occur once or twice a century.
Co-author Connie Woodhouse, a scientist at NOAA’s National Geophysical Data Center, warned that "future droughts may be much more severe and last much longer than what we have experienced this century."
Precipitation estimates gleaned from studies of tree rings in Iowa, eastern Montana, Oklahoma and eastern Wyoming indicated there were droughts as severe as the Dust Bowl in the 1750s and three times during the 19th century, from the early 1820s to the 1890s.
Those dry spells were nothing like the drought of the 16th century, however. Evidence suggests a drought started in what's now the Southwest United States around 1565 and spread to the entire western region by 1585. The scientists say they don’t know what led to the megadroughts and also don’t know enough about what causes the shorter dry spells to predict when they will occur. In fact, they acknowledged, this year’s drought in the South and Southwest caught forecasters by surprise.
Overpeck, head of NOAA's Paleoclimatology Program and the study's other author, warned that Mother Nature could get some help in creating future dust bowls.
"Besides the fact that natural variability could have more severe droughts in store for us in the future," he noted, "two human factors could make the Great Plains even more susceptible to a severe drought in the future. These are land-use practices and global warming."
Research shows that replacing natural habitat with farming or other human uses can reduce precipitation in that region. And many scientists believe that man-made emissions of "greenhouse" gases like carbon dioxide are warming the Earth.
A recent study suggests that land use is as significant a source of warming as human emissions of greenhouse gases.
Additional information on the drought study is available on NOAA's Web site.
MSNBC's Miguel Llanos and The Associated Press contributed to this report.