Study Says the Strongest El Niño in 150 Years Is Forming

Scientists say the intensifying El Niño climate phenomenon in the Pacific Ocean is on track to become the strongest in 150 years. If their alarming predictions come true, El Niño will release a massive amount of heat from the ocean, which, combined with the warming effects of human-caused climate change, could make 2027 the hottest year on record and trigger extreme weather across many parts of the globe.

California often suffers from storms and powerful waves during El Niño, leading to flooding. Image source: Mark Ralston

At a press conference held on July 23 by Berkeley Earth, a non-profit research institution based in California, climate scientist Zeke Hausfather presented a series of climate model predictions showing that the peak intensity of this El Niño could far exceed previous records, with the gap being "stunningly large."

Hausfather mentioned at the conference that the combination of this El Niño event and climate change makes it "not entirely impossible" for the global average temperature in 2027 to rise 1.7°C above pre-industrial levels. This would push global temperatures close to the 1.5°C warming threshold that countries pledged to avoid under the Paris Agreement.

The current El Niño is not surprising. The El Niño-Southern Oscillation (ENSO) is a natural fluctuation of sea surface temperatures and winds in the tropical Pacific Ocean. Historically, the phenomenon alternates between warm El Niño and cool La Niña every 2 to 7 years. The last El Niño occurred from 2023 to 2024. Earlier, meteorologists had already warned that a new strong El Niño was coming, and this year's El Niño emerged in June.

The latest predictions suggest that the intensity of this El Niño may exceed expectations. Justin Mankin from Dartmouth College in the United States said this looks very much like what scientists have predicted — that in the late 21st century, El Niño would be amplified by human-induced climate change.

Since June, the Pacific sea surface warming and strong wind patterns — hallmark features of El Niño — have been rapidly intensifying. According to the latest report from the U.S. National Oceanic and Atmospheric Administration (NOAA), there is an 80% chance that this will develop into a strong El Niño event by the end of the year, and the phenomenon is almost certain to last at least through April 2027.

"Currently, all signals indicate that the ocean-atmosphere coupling in the equatorial Pacific is very active. This gives us greater confidence that a strong El Niño will ultimately form and rank among the strongest in history," said Michelle L'Heureux, head of NOAA's ENSO prediction team.

However, NOAA's predictions may still be conservative. Hausfather compared data from 14 climate models forecasting this El Niño and found that the median prediction for peak Pacific sea surface temperature is about 0.8°C higher than the record set during the strongest El Niño on record in 2015–2016. He said, "While it's not a done deal, the likelihood of a strong El Niño is rising month by month."

Hausfather noted that in addition to El Niño potentially driving global temperatures to new highs in 2027, the warming over the next few months could also make 2026 the hottest year on record. The heatwaves, droughts, floods, and wildfires that accompany El Niño will also impact the global economy.

Mankin's team estimates that the climate anomalies caused by the strong El Niño of 1997–1998 reduced global economic growth by $5.7 trillion over the following years. If the current predictions are roughly correct, this El Niño could cause $10 trillion in economic losses by 2032.

Beyond impacting human society, El Niño will also put pressure on ecosystems and oceans, weakening their ability to absorb carbon from the atmosphere. Rising sea temperatures will also worsen the coral bleaching crisis.

Kaustubh Thirumalai from the University of Arizona said that if we look back at climate records, this El Niño may not be the strongest ever to occur on Earth. For example, coral evidence suggests there may have been an extremely strong El Niño in the 17th century. However, short-term climate events from the past are difficult to identify precisely, so conclusive evidence is lacking.

Thirumalai believes that the real significance of this El Niño occurring just two years after the last one is whether it means human-induced climate change is driving a systematic shift in the ENSO cycle. In other words, scientists already know that El Niño amplifies global warming, but is this relationship bidirectional? He said, "Frankly, we don't have a definitive answer yet."

Many climate models predict that human-caused global warming could reshape the average state of ENSO in the 21st century, making El Niño events stronger and more frequent. But researchers are still debating whether this trend is already visible in existing climate observations.

"We are in a transition period of the climate system." Thirumalai compared the ongoing climate change of this century to the Earth's massive shift from the Ice Age to a warmer world about 20,000 years ago. "The climate system has not yet reached equilibrium. It will only stabilize when humans stop emitting carbon dioxide."