Researchers have been able to construct a climate record in the tropical Pacific by studying coral growth rings. In the same way that tree rings reveal the age of centuries-old trees and the climatic influences of the past, coral growth rings in the Indian Ocean allow a long-term view of how El Niño, the warm-water phenomenon of the tropical Pacific Ocean, influences marine temperatures. Sea temperature records in the western Indian Ocean have been reliable only for a few decades, making it difficult for scientists to study long-term impact of El Niño on sea temperatures. Because coral can grow for centuries, studying the rings allows a more accurate idea of how El Niño acts as a long-term cycle. When the water is cold, the coral is saturated with oxygen. When the water is warm, the coral reveals less oxygen. Many corals die when sea temperature exceeds 94 degrees Fahrenheit. The study points to more warming and coral mortality in the future.

The study further provides forecasters with increasingly accurate models to predict the weather, as well as clues to the oceans role in the grand global climate scheme. "There are not many records of actual ocean temperatures, so adding ocean measurements to the pool, that?s one more piece of information that makes a strong case something unusual is going on," noted Julia Cole of the University of Arizona and co-author of the report on coral growth rings.