Climate Experts Have Found El Nino's Sister - la Nina

Article excerpt

BY USING awesome computing power, worldwide measurements and powerful new theories, climate specialists have found that the tropical atmosphere has a yin-yang nature: The infamous El Nino event, involving periodic warming of sea surface water in the Pacific, has a sister, La Nina.

And La Nina, it turns out, does pretty much the opposite of El Nino, being born as sea surface waters begin cooling and westerly wind speeds slow.

Although many details are still unclear, and more work must yet be done, scientists say such knowledge, plus other research data built up in the past decade, is giving several research groups the ability to predict a year in advance, with some accuracy, when the next El Nino climate event will begin in the tropical Pacific Ocean, and how long it may last.

The benefit, said Stephen Zebiak, at Columbia University's Lamont-Doherty Earth Observatory, is in the warning. El Nino can severely disturb half the globe's climate, altering rainfall and temperature patterns over South America, North America and parts of Africa and Asia.

For example, Zebiak said, after they alerted Peruvian officials that a recent El Nino was coming, officials there "made changes in the crops that would be better for wet conditions," reducing losses "very dramatically" during the event.

"We've come very far very fast," said oceanographer Mark Cane, Zebiak's colleague at Columbia. But, Cane cautioned, "the science is still very young."

The two Columbia researchers made their first successful prediction of an El Nino event that began in late 1985. They were also correct in saying El Nino would not begin in 1990, but rather in 1991-92.

"Our model has mostly worked in predicting major El Nino events; it's better than we had a right to expect, given its simplicity and how poor the data coverage is," Cane added. "We have missed some shorter-lived changes, and we don't get much detail. We're still learning."

Another team, based at the Scripps Institution of Oceanography, in the coastal San Diego community of La Jolla, reports similar success with El Nino predictions based on a more complicated computer model.

El Nino events occur roughly every four years, and have long been viewed as disruptions of "normal" climate in the tropical Pacific Ocean. In the past decade, however, scientists have come to realize that climate in the tropical Pacific changes constantly, swinging between two opposites, El Nino and La Nina.

Each El Nino event begins with rapid warming of seawater and air in a long, relatively narrow equatorial zone between Indonesia and South America. The warming usually lasts a year. But under extreme circumstances it continues for several years.

Such climate events are termed El Nino - Spanish for "The Child" - because they were first noticed as a recurring phenomenon that usually begins in South America around Christmastime. …