The fires that began burning in Indonesia this summer might have been quenched by the annual monsoons, but in 1997 the rain was too little too late. A thick coat of smog blanketed the region from Malaysia to the Philippines, and hundreds of people reportedly died of starvation and disease. The rain fell instead in places where it wasn’t wanted, blasting the Pacific coast of Mexico with hurricane Pauline, which killed 400 people and injured thousands. Elsewhere there was strange weather that was more welcome: warm waters on the coast of California lured tropical fish, while calm seas in the Atlantic put a damper on hurricanes there. In every case the prime suspect was the same: El Niño.
El Niño forms every two to seven years when the westward-blowing trade winds slacken over the equatorial Pacific. Sun-warmed water that’s usually pushed up against Southeast Asia sloshes back toward the Americas. Above that warm pool, warm, moist air rises high into the sky and forms storm clouds. The change in the heating of the atmosphere by the storms helps shift the jet streams, thereby affecting weather around the world.
Until this past year the most powerful El Niño had been the one that started in 1982, which caused $2 billion in damage from storms and floods in the United States alone. El Niño returned mildly in 1986, 1991, 1992, and 1994, but it wasn’t until 1997 that it came back with a vengeance. By October it was as big as the El Niño of 1982 and still had many months to go. This time, however, there was a difference: earlier in the year researchers had predicted that El Niño was coming.
Using data from satellites, temperature-measuring buoys, and simulations of the ocean and atmosphere, two teams of meteorologists were able to forecast El Niño’s latest arrival. To Jagadish Shukla of George Mason University in Fairfax, Virginia, this success marked nothing less than a scientific revolution. For 40 years meteorologists have been able to predict weather with reasonable accuracy a few days in advance—not individual thunderstorms, as we all know, but the bigger movements of fronts and jet streams. Now, however, we can predict climate, at least for the next season, with a very high level of confidence if there is an El Niño, says Shukla.
The benefits of knowing that El Niño is on its way can be substantial. Farmers can plant crops that will be suited to coming wet and dry weather. In Ecuador this past year, a special vaccination program was set up to protect children against waterborne diseases such as typhus. And last summer, futures traders invested heavily in wheat, on the theory that a Niño-induced drought in Australia was going to cut world supplies and drive the price way up.
Those traders took a bit of a bath, however—above normal rainfall in September and October produced a healthy Australian crop. Developments like that help explain why not everyone shares Shukla’s bullishness on El Niño forecasting. Michael Glantz, a senior scientist at the National Center for Atmospheric Research in Boulder, Colorado, says researchers still don’t understand El Niño well enough for their models to reliably forecast its consequences. The pattern of flooding and drought that one El Niño can cause may differ radically from that of the previous one, he points out. We haven't really seen all the combinations of impacts, Glantz says. It’s too early to have the level of confidence we think we have in forecasting this.
The latest El Niño is far from over, and how it plays out during the beginning of 1998 will offer one test of how well current models are doing. According to a forecast from the National Weather Service in October, we can expect drier-than-usual weather in the months to come for Indonesia, eastern Australia, Central America, the Caribbean, northern South America, and southern Africa. Meanwhile, more rain than usual will hit northeastern Argentina, Uruguay, southern Brazil, and the central and eastern equatorial Pacific. In the United States this winter, the far south should get more rain, and northern states from the Rockies to the Great Lakes can expect a warm winter. But Mother Nature can always fool you, warns oceanographer Bill Patzert at NASA's Jet Propulsion Laboratory. It’s only a probability.