MEGA DISASTERS

Large parts of the U.S. are in for a drought of epic proportions in the second half of this century, scientists warn in a new study that provides the highest degree of certainty yet on the impact of global warming on water supplies in the region.

The chances of a 35-year or longer “megadrought” striking the Southwest and central Great Plains by 2100 are above 80 percent if the world stays on its current trajectory of greenhouse gas emissions, scientists from NASA, Columbia University, and Cornell University report in a study published Thursday in the new open-access journal Science Advances.

If countries reduce their emissions to current “middle of the road” targets, the chances of a megadrought hitting the Great Plains drop to between 60 and 70 percent. But they remain nearly 80 percent for the Southwest.

That’s because rising temperatures spurred by the greenhouse effect result in more evaporation and less precipitation for the region, which is already relatively dry. (Read “Drying of the West” in National Geographic magazine.)

“Even at the middle-of-the-road scenario, we see enough warming and drying to push us past the worst droughts experienced in the region since the medieval era,” said Benjamin Cook, the study’s lead author and a scientist at NASA’s Goddard Institute for Space Studies in New York. read more