El Niño is strengthening — coral records show 36% rise since pre‑industrial era

A new reconstruction of past Pacific conditions suggests El Niño events have become noticeably stronger since the start of the industrial era, and that the rate of increase has accelerated in recent decades.

Study finds long-term strengthening linked to human-driven warming

The analysis, published in Science, concludes that El Niño is now more than 36% stronger than it was before the industrial era in the mid-19th century, with a 16% increase occurring in the last 40 years alone. Researchers warn the change appears to be accelerating as the climate warms.

El Niño — the episodic warming of parts of the tropical Pacific that reshapes weather around the world — formed a few months ago and is already being described as a "super" event. Forecasts cited by the authors indicate it could become the largest El Niño on record in the coming months, with consequences ranging from heatwaves to floods and droughts that can cause trillions of dollars in damage.

Because direct instrumental records are short (roughly 75 years), the team turned to coral archives as a "time machine" to extend the record. Chemical measurements in coral skeletons — ratios of calcium to strontium and different oxygen isotopes — provide independent estimates of the seawater conditions in which the coral grew. Uranium–thorium dating was used to establish when those coral skeletons formed.

The dataset comprises 29 fossil corals from the Galápagos Islands: 14 specimens dated to before the industrial era and 14 from the industrial and post‑industrial interval, with the oldest sample going back to about 1100 CE. The reconstruction produces a roughly 900‑year temperature record that the authors say is patchy in places but still shows a clear long‑term increase in El Niño strength.

Not all researchers accept the interpretation. Some external scientists praised the work as important and robust, while others questioned it because the coral-based signal appears to conflict with recent sea‑surface temperature observations near the Galápagos. Michael Mann, a climate scientist at the University of Pennsylvania, said the data show "a substantial decline in recent decades" in El Niño‑related variability near the Galápagos at a time when greenhouse‑gas emissions rose most sharply. John Bruno, a marine scientist at the University of North Carolina, added: "What the coral reflects is not a change in El Niño, but warming from greenhouse gases." The study authors responded that a sequence of large El Niño events — notably the enormous 1997–1998 episode and the series through 2023–24 — complicates short instrumental trends and can mask a longer‑term strengthening when analyses focus on recent decades.

Photo: press material from the event