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A study published in Science, as described in a University of Arizona report dated Aug. 28, 2026, found that El Niño events in the last 40 years were stronger than any in the 1,000 years before about 1850. The report puts the difference at nearly 40%, but does not specify the intensity metric. The finding is a comparison across the study’s reconstructed record—not, by itself, proof that human-caused warming explains the change.
What the study compared
The researchers compared recent El Niño activity with a reconstruction of the millennium before about 1850. The University of Arizona report says the study found no stronger events in that earlier interval than in the last four decades. Its nearly 40% figure describes the reported difference between the periods; because the report does not define how intensity was measured, it should not be read as a precise change in a particular temperature, wind, or rainfall measure.
The report identifies the paper as published in Science, but does not give its title or DOI. It also does not provide the underlying metric or uncertainty estimates, so those details cannot be assessed from the report alone.
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How coral records reveal past El Niño conditions
The study used cores from 13 living and ancient corals in the Galápagos Islands, where El Niño has a particularly strong influence. Coral skeletons form layers as the animals grow. The report says Galápagos corals grow about one to two centimeters per year and that researchers analyzed strontium-to-calcium ratios in the layers to infer past seawater temperatures.
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Those chemical records provide evidence about past ocean conditions. They are not direct measurements of every aspect of El Niño, such as rainfall or winds. The report does not describe the study’s full dating methods or the exact way the coral-derived temperatures were converted into its intensity comparison.
What the model analysis adds—and what it does not
Coral records show how conditions varied; they do not alone establish why. The researchers also used climate-model simulations to examine whether natural variability, volcanic activity, changes in Earth’s orbit, or atmospheric warming from fossil-fuel burning could produce similar intensification over the past millennium. The University of Arizona report attributes this modeling work to co-authors Diane Thompson and Marcus Lofverstrom.
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This analysis addresses the possibility that the recent interval reflects natural swings between more- and less-active decades. It should not be inflated into a claim that every possible natural explanation has been ruled out. The report does not provide enough model configuration or statistical detail to evaluate the attribution analysis independently.
Why the finding matters in a naturally variable climate
El Niño is a recurring natural pattern in which the tropical Pacific becomes warmer than usual. Normally, trade winds push warm water west from South America toward Australia. When those winds weaken, warm water spreads east, shifting rainfall and atmospheric circulation. The coupled ocean-and-atmosphere conditions can persist for one to two years.
El Niño also varies from decade to decade. Thompson, an associate professor of geosciences at the University of Arizona, cautioned in the report: “If you take hundreds of years, you’re going to get decades where it is more active, and you’re going to get decades where it’s less active. Sometimes it’s strong, sometimes it’s weak, all of that is normal.” The study’s central point is that the recent strong events stand out against the reconstructed millennium, not that El Niño has ceased to vary naturally.
Lead author Julia Cole, a professor and chair of the University of Michigan’s Department of Earth and Environmental Sciences, put the comparison this way: “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.” That conclusion concerns the historical comparison. The report’s summary alone does not establish a precise share of the recent intensification attributable to human influence.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What the study says about weather impacts
El Niño can shift weather far beyond the tropical Pacific. The University of Arizona report notes that it can alter U.S. storm tracks, bring wetter conditions to the desert Southwest and drier conditions to the Northwest, and raise drought or flooding risks in other regions. These are background examples of El Niño’s wider effects; the coral study did not newly quantify regional impacts or predict a specific event’s weather.
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