SHORT HISTORY OF STUDY LIMITS UNDERSTANDING OF PHENOMENON.

Byline: David R. Baker Daily News Staff Writer

For those who spent the first few months of winter wondering why climate experts disagree so often about El Nino, the answer is simple - they don't have much history to go on.

Although the phenomenon was first noticed by Peruvian fisherman well over a century ago, it wasn't until the mid-1960s that scientists first understood its potential to influence the weather worldwide. Even then, it would be years before the satellites and weather buoys that allowed forecasters to predict the current El Nino were in place.

In the 19th century, long before El Nino got its name, scientists of that day knew something interesting was going on in the atmosphere above the Pacific. They had noticed periodic changes in the region's trade winds and in monsoon cycles in Asia, but did not tie them into any larger phenomenon, said Bill Patzert at the National Aeronautics and Space Administration's Jet Propulsion Laboratory.

Similarly, the warming of ocean water that fuels El Nino was considered just a local phenomenon off the coast of Peru. Local fishermen named it after the Christ child, because its effects usually appeared around Christmas.

It wasn't until researchers compared notes following the El Nino winter of 1957-58 that they began to realize what they had on their hands.

During 1957 and 1958, unusual conditions popped up throughout the Pacific, said David Halpern, also at JPL. Some fish species disappeared from the California coast. Sea ice near Point Barrow in Alaska retreated early in the season. Hawaii weathered its first recorded typhoon.

A University of California, Los Angeles researcher named Jacob Bjerknes finally pieced it together. The warm ocean temperatures, lost fisheries and atmospheric changes were all tied together, he wrote in a 1966 paper.

``We saw that the warming off Peru sometimes wrapped its way halfway around the Atlantic,'' Patzert said.

Since then, scientific understanding of El Nino has increased dramatically. And that process should continue into coming years, as analysts pore over information from this year's event, the most thoroughly studied El Nino in history.