Another surprising drought

Drought in the Southeastern United States is a story that goes back at least 400 years to the earliest days of European settlement of the continent.  Expecting a benign New World of peace and plenty, colonists found themselves betrayed by rapidly shifting climate.

According to tree-ring analyses by climatologist David Stahle at the University of Arkansas, severe drought plagued the "Lost Colony of Roanoke" in the 1580s and the unlucky Jamestown colonists in 1607.

This history inspires comparisons with the extreme water shortages that struck the Southeast between 2005 and the winter of 2007-'08 that caused billions of dollars in agricultural losses, drained reservoirs supplying major cities and provoked legal battles among several states.  But a study in the current issue of the Journal of Climate points out that the episodes had little in common from a meteorological point of view.

To climate modeler Richard Seager at Columbia University's Lamont-Doherty Earth Observatory, lead author of the study, the troublesome recent drought was  “pathetically normal and short, far less than what the climate system is capable of generating." This rainfall reconstruction, from Lamont-Doherty, which shows the recent episode as the last brown blip, gives you an idea what the system can dish out.

"People were saying that this was a 100-year drought, but it was pretty run-of-the-mill," said Seager. "The problem is, in the last 10 years population has grown phenomenally, and hardly anyone, including the politicians, has been paying any attention.”  The population of Georgia, which uses 25 percent of the region's water, has jumped 50 percent since 1990.

While the US Southwest appears to have entered a new arid state as a result of global warming, researchers say, the Southeast droughts appear to be subject more to random changes in regional atmospheric circulation, a circumstance that makes them inherently unpredictable.

Rather than the meteorology, it was the human predicament 400 years ago that rang a bell with Stahle, who called Seager's study "a bedtime story with a moral for modern times."  The early settlers were especially vulnerable because they had just arrived and lacked sufficient backup supplies.  "Are we returning to a period of sensitivity and danger like the colonists experienced?" he asked. "In a way, yes, it looks like we are."