Researchers: La Nina may be part of bigger climate change

Wednesday, January 19th 2000, 12:00 am

By: News On 6

LOS ANGELES (AP) -- Unusual weather driven by La Nina cooling in the Pacific Ocean may be part of a larger, longer-lasting climate shift, researchers said Wednesday after analyzing new satellite data.

If the interpretation is correct, the Southern states, as well as the Southwest, could be in for 20 years or more of mild and relatively dry winters while the Pacific Northwest and the East could get socked by strong winter storms.

Measurements of sea surface temperature show warm water has been developing for the last 11/2 years in the North, West and South
Pacific. La Nina and El Nino, its warmer cousin, affect water only near the equator.

"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 NASA's Jet Propulsion Laboratory.

The Pacific Ocean's surface water temperature is a dominant force behind storm intensity as well as the path of the jet stream.

The new satellite data suggest a shift in the water temperatures. Every 20 years or so, dominant warm or cool water flip-flops for
reasons still unclear, changing weather, especially in North America.

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. El Ninos are 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.