Droughts to Become More Severe, Frequent Over Nearly a Third of Earth: Study

The Statue of Liberty, if sea level were to rise 35 meters.

As much as a third of the planet will likely experience more intense and more frequent droughts by the end of the century if global warming proceeds unchecked, according to a study released last month.

That's because warming temperatures will mean both less rainfall and less soil moisture for many of the affected areas mentioned in the study, titled "Global Warming and 21st Century Drying" and published in the March issue of the scientific journal Climate Dynamics.

Even though climate change is forecast to bring more rainfall to certain parts of the world – a phenomenon usually explained as the dry regions of the world will get drier, while the wet will get wetter – the study used the latest climate model simulations to show how higher evaporation rates can lead to droughts even in areas that see an uptick in rainfall.

The study looked at a pair of drought indices – the Palmer Drought Severity Index, commonly used to measure U.S. droughts, and the Standardized Precipitation Evapotranspiration Index – to estimate warming's impact on both changing rainfall and drying patterns worldwide.

About 12 percent of the planet will be susceptible to drought by 2100 through changes in precipitation patterns alone, the study found. That number rises to about 30 percent – an area that spans large parts of the western U.S., Europe and China – when evaporation rates are factored in.

"We know from basic physics that warmer temperatures will help to dry things out," said Benjamin Cook, the study's lead author and a climate scientist at Columbia University and NASA's Goddard Institute for Space Studies, in an interview with The Hindu.

This not only will mean worse drought for areas already subject to it, the study's authors add, but also in areas that are forecast to become wetter.

"For agriculture, the moisture balance in the soil is what really matters," said study co-author Jason Smerdon, a climate scientist with Columbia University's Lamont-Doherty Earth Observatory. "If rain increases slightly but temperatures also increase, drought is a potential consequence," he told The Hindu.

See the entire article here: http://www.weather.com/news/science/environment/global-warming-may-spread-drought-third-earth-20140401