Adios, Maybe, to El Ni

The freakish spate of global bad weather could be ending

The radio signals that arrived in Washington, D.C., last week from weather satellites drew a rapt audience of oceanographers and meteorologists. Reason: the transmissions showed that a villainous, once-in-a-century temperature rise in the waters of the eastern Pacific Ocean, which scientists blame for a costly year of cockeyed weather around the globe, has finally begun to disappear.

El Nino, a reference to the Christ Child, is a warm current of equatorial water that usually appears off the coast of South America around Christmas. Its impact on annual weather patterns is generally minor. But the present El Nino began late in the spring of 1982, when atmospheric pressure at the western edge of the Pacific inexplicably began to rise, while air pressure was dropping along coastlines in the Americas. The resulting pressure gap reduced the strength of the Pacific trade winds, which normally blow warm surface waters westward, away from the Americas. As air-pressure levels seesawed across the Pacific, the trade winds not only weakened but actually began to blow in reverse, and warm waters sloshed eastward toward the Americas. In some areas of the Pacific last December, the surface temperature rose by 7DEG, to 85DEGF. Last May the readings were more than 11DEGF above normal, the largest recorded increase in 100 years.

The wind and temperature shifts, transmitted through the atmosphere and interconnected oceans, disrupted global weather; some scientists believe that is contributing to the unseasonably hot summer east of the Rocky Mountains. Storm centers moved to new paths in mid-Pacific, causing unusual storms in Hawaii and the worst recorded hurricane in the history of Tahiti. Peruvian officials estimate that overheated ocean waters destroyed about one-half of that nation's normal commercial fishing catch. Winds, waves and storms smashed California beaches last winter, while Australia, Indonesia, the Philippines, Sri Lanka, southern Africa and southern India all suffered from drought. "A year of natural catastrophe," says M. Peter McPherson, director of the U.S. International Development Cooperation Agency, which has provided $60 million in emergency aid to flooded Andean nations.

But now, observes Mark Cane, associate professor of oceanography at the Massachusetts Institute of Technology, "there are a lot of signs that things are returning to normal." The atmospheric pressure gap between the eastern and western Pacific has eased, and trade winds are again blowing normally, from the east. Sensors in drifting buoys have recently recorded water temperatures in the mid-Pacific of 81DEGF, down by nearly 8DEGF from their May highs. Along the South American coast, waters remain unnaturally warm (as much as 6DEGF above their normal 78DEG), but the waters have slowly begun to cool since May, and scientists expect the trend to continue.

Meteorologists still do not understand why El Nino arrives in cycles, causing extreme heatings of ocean temperatures every four or five years. The El Nino of 1972, though less severe than the present one, nevertheless crippled the South American fishing industry. Although few of these episodes last longer than a year, two-year El Ninos were recorded in 1877-79 and in 1940-42. Meteorologist Oswaldo Garcia notes that there are some disturbing similarities between the present El Nino and the 1877 episode, which may have contributed to flooding in California and a warm winter in the U.S., followed by an unusually hot summer. Eugene M. Rasmusson, a climate analyst at the National Weather Service in Washington, D.C., says that he and his colleagues "will be watching very closely through the autumn" just in case the present El Nino should gain a second wind. But with fingers only slightly crossed, Rasmusson adds: "The odds are very strongly against that." This file is automatically generated by a robot program, so viewer discretion is required.