Researchers Warn of Climate Change...01/20/00
By Matthew Fordahl  The Associated Press

LOS ANGELES - The Pacific Ocean may be undergoing a dramatic temperature change that could make the unusual weather patterns of the last 18 months the norm for the next 30 years, researchers say.

Winters that are dry and warm in the Southwest, unusually frigid in the East and rainy in the Northwest are often associated with La Nina, a cooling in the Pacific near the equator. It is the opposite of El Nino, best known for bringing rain to California.

Satellite data released Wednesday suggest that something bigger and longer-lasting is happening in the ocean that covers one-third of the Earth. For the past 1 1/2 years, an area of warming is developing in the North, West and South Pacific. Wedged in between is the cooler water known as La Nina.

''The persistence of ... warmer and colder than average ocean temperatures, tells us there is much more than an isolated La Nina occurring in the Pacific Ocean,'' said William Patzert, an oceanographer at the NASA's Jet Propulsion Laboratory.

Patzert believes the ocean-wide temperature changes indicate a natural shift that occurs every 20 to 30 years called the Pacific Decadal Oscillation. Dominant warm or cool water flip-flops for reasons still unclear, changing weather worldwide.

One result of the shifts is that conditions favor either El Nino or La Nina. Since the 1970s, the ocean has been in what is called a positive phase, marked by warm surface water in the tropics and cooler water in the North Pacific, making El Ninos more common.

But many experts argue it's too early to make any conclusions. The unusual ocean temperatures may be from a lingering La Nina and not necessarily a sign the Pacific is entering a negative phase of cool tropical water and warm North Pacific temperatures.

''The point is it won't be for another 10 years before we can say with confidence that we've undergone a regime shift,'' said Wayne Higgins, senior meteorologist at the U.S. Climate Prediction Center in Camp Springs, Md.

David Battisti, atmospheric sciences professor at the University of Washington, agreed.

''It is not at all clear that the pattern that is seen this particular winter is part of a decadal change, he said.

The latest ocean surface temperature readings were taken from the French-U.S. satellite Topex-Poseidon, which measures sea-surface height used to calculate the temperature at the surface.

Unlike daily weather reports in newspapers and television, climate prediction is about long-range trends and probabilities. During a La Nina winter, for instance, it is more likely the Pacific Northwest will be soaked while the Southwest is dry.

Though far from precise, climate predictions can provide warning for farmers, water managers and emergency planners.

''For the last 20 years, California has had above-normal rainfall and Seattle has had milder weather and less rainfall,'' Patzert said. ''Now we're going back to the good old days when it was really dry in California and really stormy in Seattle.''

Patzert concedes that it is an early prediction, but one that benefits the public by starting the debate early. Sooner or later, the ocean is going to change.

''I think it's an interesting thing to put out for the American people to think about,'' he said. ''It's educational and everybody will definitely hear about it in the next year or two.''