July 2, 2009

Equatorial rains are moving northward

A U.S. study indicates bands of heavy rainfall occurring near the equator have been moving northward for more than 300 years, probably due to a warmer world.

Researchers from the University of Washington base their findings on sediment cores taken from lakes and lagoons on Palau, Washington, Christmas and Galapagos islands.

The scientists say if the bands continue to migrate at slightly less than a mile a year, some Pacific islands near the equator might become drier within decades and starved of freshwater by mid-century. But the prospect of additional warming because of greenhouse gases means that situation could occur even sooner, the scientists said.

We're talking about the most prominent rainfall feature on the planet, one that many people depend on as the source of their freshwater because there is no groundwater to speak of where they live, said Associate Professor Julian Sachs, lead author of the study. "In addition many other people who live in the tropics, but farther afield from the Pacific, could be affected because this band of rain shapes atmospheric circulation patterns throughout the world.

The study that included Dirk Sachse, Rienk Smittenberg, Zhaohui Zhang, Stjepko Golubic and Professor David Battisti appears in the July issue of the journal Nature Geoscience.