Cousin of El Nino Haunts Indian Ocean

Article excerpt

For decades, climate researchers have regarded the Indian Ocean as a boring basin, lacking the commotion that El Nino and La Nina stir up in the Pacific. Now, two teams of scientists have independently identified the climatic kin of El Nino in the Indian Ocean, where it caused widespread weather problems in 1997.

The finding raises the hope that forecasters will soon learn to predict abnormal torrents and droughts in East Africa, India, and Indonesia.

"It's like we've found a raw gem. Now, we have to polish it and see how good it is," says Peter J. Webster of the University of Colorado at Boulder, the leader of one team. His group published its results in the Sept. 23 NATURE, as did a trio of Japanese and Indian researchers.

The two sets of scientists noticed that water temperatures along the equatorial Indian Ocean have a habit of flip-flopping. Usually, warm water accumulates in the eastern part of the ocean near Indonesia, while the western section near Africa remains relatively cool. This pattern can occasionally reverse, however, when winds and ocean currents conspire to chill the eastern Indian Ocean, contend the scientists.

Historical data show this kind of extreme turnabout has happened six times in the past 40 years, reports Toshio Yamagata at the University of Tokyo and his colleagues. When the western Indian Ocean warms dramatically, it can bring devastating rains to Kenya and neighboring countries, which in turn spawn epidemics there (SN: 7/17/99, p. 36).

Scientists had previously detected hints of this temperature reversal while studying the climate of 1961, a catastrophically wet year in East Africa. They had, however, thought that the 1961 episode was unique, says Webster. The pattern sprang to life again in 1997 but got overshadowed by the century's biggest El Nino.

"All of the commentaries in 1997 and 1998 were referring to the great El Nino, and here we had this enormous temperature variation in the Indian Ocean, and nobody had noticed it," says Webster. …