Scientists at Columbia University’s Lamont-Doherty Earth Observatory, Cornell University and NASA provide new insights into the role temperature plays in megadrought risk and how our choices today can affect water resources in the future. “By the end of the century, the real controlling influence on megadrought risk will be temperature. That stands out very starkly against precipitation projections that can vary quite a bit,” said study co-author Jason Smerdon, a climate scientist at Columbia University’s Lamont-Doherty Earth Observatory. “What really seems to drive the drying in terms of future projections is the magnitude of the mean temperature increases.” In an earlier paper, the scientists analyzed several climate models and 2,000 years of climate data from tree ring reconstructions and found a high chance that an extended drought lasting 35 years or longer, a megadrought, would hit the Western or Central United States during the second half of this century if global temperatures continue to rise. For the new study, published this week in the journal Science Advances, they explored the forces driving that risk, focusing on soil moisture and the relative roles of temperature and precipitation. The scientists found that even if the Southwest receives more precipitation than it does today, rising temperatures will still push the region’s megadrought risk above 70 percent by the end of the century if the world continues on a high-emissions growth path. That rises to 90 percent if precipitation levels are unchanged. If the Southwest gets less precipitation, a more likely outcome according to most climate models, the megadrought risk rises to 99 percent across most of the region.
From Columbia University Photo Credit John Vlahakis