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
"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
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. …