Environment

Courtesy of Space Imaging Near Manaus, Brazil (top), the Rio Negro (black) meets the Amazon River (brown). Scientists used satellite data and river flow measurements to determine rainfall in the Amazon River basin.

Can two of the world’s mightiest rivers, 2,600 miles apart, share rainfall? MIT civil and environmental engineer Elfatih Eltahir studied readings from NASA’s Tropical Rainfall Measuring Mission and found that—statistically at least—there is a seesaw effect in rainfall between the Amazon and the Congo river basins. When there is a drought along the Congo, there are floods in the Amazon, and vice versa. “It looks somewhat obvious after you discover it,” Eltahir says, “but nobody looked at the [satellite] data before.”

The question now is, what does it mean? “At the moment it’s an interesting statistical relationship, but there’s still no predictability,” says Anne Waple, a research climatologist at the National Oceanographic and Atmospheric Administration’s Climate Monitoring Branch. “It could even be that this is symptomatic of a larger process. It could be the effects of, rather than causes of, an oscillation.” Nonetheless, if scientists can figure out what causes the pattern, they may be able to warn of devastating floods or droughts. “We need to understand the mechanism,” Eltahir says. “How does this happen? What’s the global reach? What’s its global impact?”