Analyzing aridity in the western U.S. over the past 1,200 years, the study team, which also included scientists from the University of Arizona, University of Arkansas, and NOAA, found evidence suggesting that elevated aridity in the U.S. West may be a natural response to climate warming. "The Western United States is so vulnerable to drought, we thought it was important to understand some of the long-term causes of drought in North America," said lead author Dr. Edward R. Cook of the Lamont Doherty Earth Observatory's tree ring laboratory.
The study revealed that a 400-year-long period of elevated aridity and epic drought occurred in what is now the western U.S. during the period A.D. 900-1300. This corresponds broadly to the so-called "Medieval Warm Period," a time in which a variety of paleoclimate records indicate unusual warmth over much of the Northern Hemisphere. The authors of the new study argue that there are climate mechanisms involved that make warming climate conditions likely to lead to increased prevalence of drought in the western, interior region of North America.
Looking at implications for the future, the authors express concern. "Any trend towards warmer temperatures in the future could lead to a serious long-term increase in aridity over Western North America," they write in the paper.
Co-author Dr. David Meko of the University of Arizona tree ring lab notes that the drought that has gripped the western United States for the past four years "pales in comparison with so
Contact: Mary Tobin
The Earth Institute at Columbia University