EARTH: Widely used index may have overestimated drought

(Press-News.org) Alexandria, VA – For decades, scientists have used sophisticated instruments and computer models to predict the nature of droughts. With the threat of climate change looming large, the majority of these models have steadily predicted an increasingly frequent and severe global drought cycle. But a recent study from a team of researchers at Princeton University and the Australian National University suggests that one of these widely used tools — the Palmer Drought Severity Index (PDSI) — may be incorrect.

The PDSI was developed in the 1960s as a way to convert multiyear temperature and precipitation data into a single number representing relative wetness for each region of the United States. The PDSI, however, does not originally account for potential evaporation, which depends on solar radiation, wind speed and humidity. The new model developed by Justin Sheffield, a hydrologist at Princeton and the lead author of the study, and his team accounts for this deficiency, and is subsequently producing different numbers. Has the reported increase in drought over the last 60 years been overestimated? And what might that mean for the future?

### Read the full article online at http://bit.ly/ZiHCWi.

Check out other great articles in the April issue of EARTH Magazine. Rethink continental collisions, reveal eye and hair color with ancient DNA, and discover a new link between fire and ice all in this month's issue of EARTH.

Keep up to date with the latest happenings in Earth, energy and environment news with EARTH magazine online at http://www.earthmagazine.org/. Published by the American Geosciences Institute, EARTH is your source for the science behind the headlines.

The American Geosciences Institute is a nonprofit federation of geoscientific and professional associations that represents more than 250,000 geologists, geophysicists and other earth scientists. Founded in 1948, AGI provides information services to geoscientists, serves as a voice of shared interests in the profession, plays a major role in strengthening geoscience education, and strives to increase public awareness of the vital role the geosciences play in society's use of resources, resiliency to natural hazards, and interaction with the environment. END