Corals Reveal El Niño Events Have Become Stronger in Recent Decades, Probably Because Humans Have Been Heating Up the Planet

Coral records from the Galápagos Islands indicate that El Niño’s natural climate fluctuations have become more intense in recent decades, adding new evidence to concerns about a warming planet’s influence on the Pacific phenomenon. The findings arrive as forecasters watch a developing 2026 El Niño that has been described as potentially “super,” with its eventual scale still uncertain. Scientists say the coral archive offers a much longer view than modern weather measurements alone can provide.

The research examines chemical signals locked into coral skeletons over centuries of growth. As corals build their hard structures, they incorporate trace elements from surrounding seawater. Those variations can preserve clues about changes in ocean conditions, allowing researchers to reconstruct shifts in tropical Pacific climate far beyond the era of satellites, instrument buoys and formal weather records.

Using that natural archive, the team traced climate variability across roughly the last 1,000 years. Their reconstruction suggests that El Niño-related swings during the past four decades have been larger than those seen in the preindustrial period. The comparison is important because it places the recent changes against a long baseline, rather than judging them only against the shorter period of modern observation.

The coral work draws on an extensive collection effort. Researchers associated with the project have gathered thousands of samples since 2006, including specimens used to build the Galápagos record. Julia Cole of the University of Michigan is among the scientists connected with that sampling effort. The resulting material gives investigators multiple coral histories to compare as they look for patterns that extend across the region and through time.

El Niño is part of a recurring Pacific climate cycle that can reshape weather well beyond the ocean itself. Changes in tropical Pacific waters and atmospheric circulation can influence rainfall, drought, heat, storms and marine ecosystems in many parts of the world. Because the event’s effects can reach food production, water supplies, public health planning and disaster preparation, scientists have long sought to understand whether global warming may alter its strength.

The new analysis points toward a notable change after the expansion of fossil-fuel use in the middle of the 19th century. Burning coal, oil and gas releases carbon dioxide, which retains heat in the atmosphere and drives long-term global warming. The study does not claim to prove that human-caused climate change is responsible for the apparent intensification of El Niño variability. Instead, it identifies human-driven warming as the most plausible explanation for the trend seen in the corals.

That distinction remains significant. El Niño has always varied naturally, and a single powerful event cannot by itself establish a permanent shift in the climate system. Coral evidence can show how recent behavior compares with earlier centuries, but researchers must still account for the complexity of ocean-atmosphere interactions and the limits of any reconstruction. Continued monitoring of the present event and future events will help test whether the stronger variability persists.

Independent climate scientist Kim Cobb of Brown University, who did not take part in the study, described the work as a timely contribution to the question of how climate change may affect El Niño intensity. Speaking to CNN, Cobb said the research provides additional support for the possibility that human warming contributes to the unusually large scale of recent events. Her assessment also underscored the immediate uncertainty: observers are still waiting to learn how powerful the 2026 El Niño ultimately becomes.

The study was published in Science on August 27. Its broader implication is not that every future El Niño will necessarily follow the same pattern, but that the background conditions in which these events occur may be changing. As communities prepare for the weather disruptions associated with the current Pacific shift, the ancient coral record offers a reminder that recent decades may not be fully explained by natural variability alone.

Source: Smithsonian Magazine