Study warns of mega drought to come

The longest drought in any living Texan's memory lasted seven years in the 1950s. Without rain, the state lost 100,000 farms and ranches as the rural population moved into cities, unable to make a living off the dry land. But there could be worse to come. A recent study led by a NASA scientist found a substantial likelihood for a decades-long drought later in the 21st Century. "We found that global warming is very likely to lead to long-term drying in Western North America," said Benjamin Cook, a researcher with NASA Goddard Institute for Space Studies. "Not only drier than the 20th Century--it might be drier in the future than really extreme periods in the 12th and 13th centuries."...Tree rings tells scientists about the past, and ancient trees and tree stumps in the American West clued researchers into Medieval mega droughts that are thought to have turned much of the region's grassland to the desert it is today. Seager said thousand-year-old trees are easy to find in the American West, but three or four thousand-year-old ones are exceptionally rare, providing little insight into whether disastrous droughts happened deeper in the past. However, he said fossilized dunes give evidence of a giant dusty desert between Texas and Canada four to six thousand years ago. Those dryspells trump Texas' recent damaging droughts, and Cook said human activities have made them more likely to strike again. "We analyzed a situation for the future that assumes greenhouse gasses continue along their current trajectory," Cook said. "The models for the Southwest pretty much uniformly show this strong drying trend in the late half of the 21st Century."...more