Strong El Niño events occurred more frequently over the past century than during the preceding 1,000 years, according to a reconstruction of eastern Pacific sea surface temperatures published in Science and reported by Nature.
Julia Cole, a palaeoclimatologist at the University of Michigan in Ann Arbor, led the analysis using coral skeletons collected from the Galápagos islands. The researchers reconstructed ocean conditions across the millennium before industrial greenhouse-gas emissions began warming the planet, finding that recent shifts depart from long-term natural patterns. Cole noted that the increase in strong events does not look like a fluke.
Pacific waters developed El Niño conditions this June, with forecasts projecting the cycle will become a record-breaking event by a wide margin. The current warming marks the third strong El Niño in 11 years, a frequency never recorded before. The warm phase of the natural El Niño–Southern Oscillation temporarily elevates global average temperatures, altering weather patterns with direct effects on ecosystems and economies.
Researchers previously faced hurdles evaluating historical trends because reliable temperature measurements across remote tropical Pacific waters were rare before the twentieth century. While corals from the central Pacific pointed to rising frequency in recent decades, they failed to capture the eastern Pacific where warming is strongest. Julien Emile-Geay, a palaeoclimatologist at the University of Southern California in Los Angeles, likened measuring the system only from the central Pacific to placing a stethoscope on an ankle to track a heartbeat.
The Galápagos islands sit directly in what Cole described as the heart of El Niño, though extreme conditions in that region limit where corals can grow. While climate models project that strong events will continue to become more frequent as global temperatures rise, Cole noted that corals provide a view into the past rather than a forecast tool for future ocean-atmosphere feedbacks.
