Yale Study Challenges the Idea of 'Permanent El Niño', Says Tropics will Get Warmer in Future

A new study by Yale University researchers challenges the idea that the Pacific Ocean experienced "permanent" El Niño-like conditions in the past. The research suggests that rise of greenhouse gases will lead to higher temperatures in the tropics.

El Nino is characterized by warm temperatures in the equatorial Pacific and low overall temperature gradient in the Pacific. During extreme El Nino events, such as the ones that occurred in 1982-83 and 1997-98, weather patterns across the world go haywire, leading to sparse rains in some regions to extreme flooding in others.

"There's good news and bad news about future global warming," said Mark Pagani, professor of geology and geophysics at Yale.

"The good news is that global warming does not drive the Pacific Ocean into a permanent El Niño-like condition with all the other regional climate impacts that come with that. The bad news is that the tropics will warm as we continue to add greenhouse gases to the atmosphere - and the recent past was probably much warmer than generally assumed," Pagani added, according to a news release.

Currently, other researchers believe that sea surface temperatures in the western Pacific remained constant for millions of years. This western "warm pool" is one of the hottest regions of the Pacific. This warm pool of water, according to current theory on El nino, acted as temperature control, stabilizing heat transfer in the Pacific.

Pagani and team have now constructed a model that accounts for conditions in the Pacific for some 12 million years. Researchers found that Pacific warm pool temperatures were about 4°C warmer millions of years back than they are now. The study shows that in the distant past, the entire Pacific ocean warmed up, rather than just pockets of water, as was thought earlier. In other words, the study shows that there was no tropical temperature control mechanism or "permanent El Niño-like" conditions 12 million years ago.

"El Niño conditions today are characterized by very low equatorial Pacific temperature gradients," Pagani said. "It seemed from previous data that the equatorial Pacific maintained similarly low temperature gradients in the past and thus reflected a 'permanent' state characteristic of the modern El Niño."

Understanding ancient weather systems could help us better understand and prepare for the temperature fluctuation of the future, researchers said.

The study is published in the journal Science and was supported by The Schlanger Fellowship (U.S. Science Support Program for IODP) and the National Science Foundation.