Climate change is making El Niño stronger and more dangerous than ever before, scientists warn.

In a new study, researchers have revealed that El Niño events have become nearly 40% stronger over the past four decades than they were in the preindustrial era.

The finding comes as the world is in the grips of a historic "super" El Niño. While daily average sea surface temperatures soar to unprecedented highs, forecasters have become almost certain that the 2026 to 2027 El Niño will be an all-time record event.

"We don't see a time in the past where El Niños have been as strong as today, and we show that the strength of El Niño changes in parallel with the warming of global temperature," study first author Julia Cole, a professor and chair of the Department of Earth and Environmental Sciences at the University of Michigan, said in a statement. "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."

El Niño events occur every two to seven years as part of the Pacific Ocean's El Niño-Southern Oscillation (ENSO) natural climate cycle. The ENSO cycle flips between the warmer El Niño phase and the cooler La Niña phase, with neutral periods in between.

El Niño periods bring elevated sea surface temperatures in the central and eastern Pacific, thereby weakening or reversing trade winds and strongly disrupting global temperatures and rainfall patterns. Earth's last El Niño ran from June 2023 to April 2024, delivering an injection of heat to our already warming world that made 2024 the hottest year on record.

The impacts of El Niño periods can be profound, with studies linking the events to famine in Europe, civil wars in tropical regions, and droughts, floods and forest fires around the world.

Climate scientists have long suspected a link between the growing intensity of recent El Niño events and global warming. But sparse instrumental records and significant variability in the natural climate pattern has made it difficult to say so for certain.

So in the new study published Aug. 27 in the journal Science, researchers investigated whether climate change has been boosting the severity of recent El Niño events. The team analyzed 13 ancient and modern corals taken from close to the events' epicenter — the Pacific Ocean's Galápagos Islands.

By analyzing the temperature-sensitive chemistry of the coral samples, the scientists discovered a millennium-spanning pattern of lower intensity El Niño events being gradually superseded by ones of increased strength after humanity's widespread adoption of fossil fuels in the 19th century. Using climate simulations, the researchers ruled out the possibility that natural causes, such as volcanic eruptions or solar variability, could have caused this shift.

"We kept adding records thinking well, this is going to get more complicated, but it really didn't," Cole said. "This is such a clear story."

The prospect of El Niño and climate change feeding back into each other is troubling, the researchers said, especially as the climate pattern has the potential to drive persistent shifts in major ecosystems such as the Amazon rainforest.

"El Niño is a really big source of climate extremes, and so if it's getting stronger, the impacts are getting stronger. Impacts like droughts, floods, wildfire and food insecurity," Cole said.

In the short term, the combination of climate change and El Niño could bring significant strain to our warming planet.

"The question is not whether the current El Niño is going to happen, but how bad is it going to be, and how bad will the impacts be?" Cole said. "This event is superimposed on global warming, and it's likely to supercharge the temperature increase that we would normally see from greenhouse gases."

The findings further underscore the urgent need to mitigate further global warming, Cole noted.

"No country has the resources to be fully protected from these impacts. This is one more reason we need to move away from fossil fuels, the root cause of the problem," Cole said.