University of Rochester

Physicists Predict Super-Niņo: 15-Year El Niņo / La Niņa Cycle

April 3, 2002

El Niņo, the shift in ocean temperatures that was blamed for dozens of natural disasters in 1998, may be an oscillation in a much larger cycle of climate change that physicists at the University of Rochester have dubbed "Super-Niņo." David Douglass, professor of physics, believes that El Niņos and their counterparts, La Niņas, are governed by a complex 15-year cycle. He and his colleagues have mapped out the pattern of the temperature fluctuations and found that in the last 18 months since the pattern was determined, actual climate measurements are consistent with their Super-Niņo predictions.

The Super-Niņo is an alternating sequence of El Niņos and La Niņas with a duration of about 15 years, unless some other major climate change intervenes. Douglass' team has noted three sequences since 1968, with the latest one beginning in 1994. The sequence suggests that a major El Niņo event, though not as large as the 1998 event, is likely to occur this year.

"When we created this model back in July 2000, we estimated that we'd be off by as much as 50 percent," says Douglass. "But as we've been pulling the data together over the last several months, we've found that the actual ocean fluctuations were quite close to our predictions."

The Super-Niņo research came about as Douglass' team was investigating how the Earth's temperature changes in relation to the energy output of the Sun. In order to get a fix on which temperature changes were sun-related, Douglass had to weed out other sources of global climate change such as El Niņo. The team decided that what was understood about El Niņo was not accurate enough for its needs, so the members advanced the research themselves.

During El Niņo the major winds in the central and western Pacific ebb, and this causes a rise in the temperature of the ocean's surface. Rainfall follows the warm water eastward across the Pacific, bringing floods in Peru and droughts in Indonesia and Australia. The vast alteration of atmospheric heat results in large changes in the global atmospheric circulation, which in turn force changes in weather in regions far removed from the tropical Pacific. Douglass looked at oceanic data dating back to the late 1960s to determine if this change of ocean temperature happened in a manner he could predict and eliminate from his solar-heating model.

Douglass found that since 1968, three major El Niņo events happened roughly 15 years apart, followed by two lesser peaks interspersed with La Niņas. The next temperature peak, according to Douglass' data, is due this summer and will be roughly two thirds as warm as the 1998 El Niņo.

Douglass' model does have a limitation, however. Though the Super-Niņo cycle lasts about 15 years, there is no way to predict when that cycle will begin.

"We're about two thirds of the way through a cycle now, so we can predict only to the end of it-around five years," says Douglass. "The predictive power of this model only comes into play once the Super-Niņo has begun. Once that 15-year cycle has played out, we don't know if the next onewill start immediately, or years down the road."

Climatologists usually forecast 9 to12 months ahead, revising their predictions every month or so. Douglass acknowledges that his specialty is condensed matter physics and not climate forecasting. However, a year and a half ago his research predicted a new, medium-sized El Niņo occurring this summer, which many climatologists are now also predicting.




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