Scientists at the University of Arizona reviewed the region's past temperatures and droughts to find out when and for how long drought and warm temperatures coincided in the past, and said a 60-year drought like one in the 12th century is possible, ScienceDaily.com reported Monday.
During the medieval period, high temperatures coincided with lengthy and widespread droughts in the region, researches said.
The last 2,000 years have seen several periods of severe and sustained drought affecting much of western North America, the scientists said.
"Major 20th century droughts pale in comparison to droughts documented in paleoclimatic records over the past two millennia," the researchers wrote in the online edition of the Proceedings of the National Academy of Sciences.
"We're not saying future droughts will be worse than what we see in the paleo record, but we are saying they could be as bad," lead author Connie A. Woodhouse, a UA associate professor of geography and regional development, said. "However, the effects of such a worst-case drought, were it to recur in the future, would be greatly intensified by even warmer temperatures.
"Even without warming, if you had one of those medieval droughts now, the impact would be devastating," she said. "Our water systems are not built to sustain us through that length of drought."