With a potentially historic “Super” El Niño underway in the Pacific, estimated to peak during the Northern Hemisphere’s coming fall and winter, researchers are looking to environmental records to put the event into a broader perspective.
By studying corals in the Galápagos Islands and using climate models to reconstruct the past, researchers from the University of Michigan (UM) found that El Niño events over the past 40 years were stronger than any in the 1,000 years before the Industrial Revolution.
As described in their paper published in Science, the researchers found an almost 40 percent increase in El Niño intensity over the past four decades. The findings could help scientists understand how the phenomenon may change as global temperatures continue to rise and what that could mean for future climate extremes.
“We don't see a time in the past where El Niños have been as strong as today, and we show that the strength of El Niño changes in parallel with the warming of global temperature,” said lead study author Julia Cole, professor at UM’s Department of Earth and Environmental Sciences, in a news release. “Our findings tell us that the big El Niño events of the last 40 years are not normal in the context of the last thousand years.”
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What Causes An El Niño?
Ancient corals like these at Urvina Bay in the western Galápagos preserve a history of ocean temperature going back millennia.
(Image Credit: Julia Cole, University of Michigan)
El Niño is a natural climate phenomenon that occurs every few years, when the tropical Pacific becomes warmer than usual (the formal scientific name is ENSO: Pacific El Niño–Southern Oscillation). Usually, trade winds push warm surface water westward toward Australia and Indonesia. When those winds weaken, warm water spreads eastward toward South America, shifting rainfall patterns and reinforcing the weakened winds.
Although El Niño begins in the tropical Pacific, its effects can ripple around the world. In the U.S., storm tracks can shift southward, with a rainier Southwest and drier conditions in the Northwest. Overall, these changes can contribute to droughts and flooding, increasing the risks of crop failures, wildfires, and disease around the world.
“The question is not whether the current El Niño is going to happen, but how bad is it going to be, and how bad will the impacts be?” Cole said. “This event is superimposed on global warming, and it's likely to supercharge the temperature increase that we would normally see from greenhouse gases. There are forecasts that we might get as hot as 1.7 or 1.8 degrees Celsius above pre-industrial temperatures, which is quite a bit higher than the current record.”
Reading El Niño’s History in Corals of the Galápagos Islands
To see how unusual recent El Niños are, the team analyzed 13 coral samples from the Galápagos, including living colonies and ancient coral boulders. Corals build their skeletons layer by layer as they grow, preserving chemical clues about the seawater around them. By analyzing those layers, the researchers reconstructed temperature changes and El Niño activity over much of the last millennium.
The record showed a striking pattern: Strong El Niños occurred repeatedly during the past 40 to 50 years, while earlier events were generally less intense.
“We kept adding records thinking, well, this is going to get more complicated, but it really didn't,” said Cole. “This is such a clear story.”
The team then used climate models to test whether natural factors, including volcanic eruptions and changes in solar activity, could explain the recent shift. They found no evidence that natural processes alone could have produced such a large increase in El Niño intensity over the 1,000 years prior to 1850.
A Warmer World, Stronger Extremes?
The findings suggest that global warming may be amplifying El Niño, potentially making an already disruptive climate phenomenon even more powerful.
Stronger El Niños can mean more severe droughts, floods and wildfires, along with food insecurity, infrastructure damage and increased risks of diseases such as cholera, the authors explain in the statement.
“We believe global warming is supercharging El Niño, and if that's true, then we expect stronger climate extremes that will amplify ecological, infrastructural and human losses,” added Cole. “No country has the resources to be fully protected from these impacts. This is one more reason we need to move away from fossil fuels, the root cause of the problem.”
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Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
- This article references information from a study published in Science: Recent strengthening of eastern Pacific ENSO in the last millennium paleorecord
