The tropical rain band that encircles Earth just north of the equator affects rainfall patterns worldwide. By taking sediment cores from pond and lake beds on tropical islands, scientists can determine where the band has been since A.D. 800 and where it may move in the future. At current global warming rates, the band could shift north 5 degrees by 2100, drying out Ecuador, Columbia and the U.S. Southwest.

Obtaining the data from such remote locations often requires on-the-spot ingenuity. Julian P. Sachs, an associate professor of oceanography at the University of Washington in Seattle School of Oceanography, and Conor L. Myhrvold, a geoscience major at Princeton University, share photos from recent expeditions.

View a slide show of photos of the data gathering.