The 2002-03 El Niño has resisted stereotypes with its unpredictable behavior.

Sometimes Earth scientist Bill Patzert wishes he had a degree in psychology. It might help him understand El Niño.

"Every El Niño has a personality all its own, and the latest one has been very quirky," says Patzert, who works at NASA's Jet Propulsion Laboratory. "Here in southern California we expect El Niño to bring heavy rains. But the weather this winter has had a split-personality, alternating between warm and dry months to very cold and wet months."

Strange. But it's not just southern California. Other parts of the world have had quirky El Niño weather, too.

El Niño is a global weather disturbance that comes along every 4 to 7 years when trade winds blowing across the Pacific Ocean weaken or even reverse. (Why they do this, no one knows.) Normally these winds blow from the Americas toward Australia, pushing sun-warmed surface waters from east to west. "Warm water accumulates near Australia in a region we call 'the warm pool,'" says Patzert.

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