El Niño events are now more powerful than at any point in the past millennium, according to a study published in the journal Science. The research draws on a natural archive embedded in coral skeletons to show that human-caused climate change is intensifying one of the world's most consequential weather patterns.
The El Niño Southern Oscillation (ENSO) is a recurring shift in sea surface temperatures and winds across the tropical Pacific. It disrupts rainfall, drives droughts and floods, and affects weather far beyond the Pacific basin. Understanding how it is changing matters for billions of people.
The new study reconstructed sea surface temperatures over the past 1,000 years using high-resolution geochemical measurements taken from modern and fossilised corals in the Galápagos Islands. The Galápagos lie in the eastern tropical Pacific, where El Niño produces some of its strongest effects, making the islands an unusually well-placed natural recorder of ENSO history.
Coral skeletons preserve chemical signals as they grow, layer by layer, year by year. Those signals track the temperature of the surrounding water, giving scientists a detailed picture of ocean conditions stretching back centuries before instrumental records began.
The findings are striking. EurekAlert reports that modern ENSO variability in the eastern Pacific is 36.5% higher than during the preindustrial millennium, driven by more frequent and stronger El Niño events. The sharpest rise has come in the past 40 years.
To rule out natural causes, the research team compared their coral-derived record against preindustrial climate simulations from 12 climate models. The study found that the observed increase exceeded what natural variability alone could explain, pointing to human-caused warming as the driver.
Scientific American reports that Julia Cole of the University of Michigan was a co-author of the research. The paper was published with the digital object identifier 10.1126/science.ady2660.
Whether other ocean regions show comparable trends remains an open question. What the coral record does establish, the researchers say, is that the modern era has moved well outside the range of the past thousand years.
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