El Niño’s closer hit—then a more dangerous future

There is an 80% chance an El Niño will develop by September, with most forecasts pointing to a moderate event. But new research warns that even if future El Niños aren’t stronger, their impacts will still intensify in a warming world—and studies suggest ENSO s

Waves already look different when El Niño is in charge. In 2016, supercharged waves battered the California coast—an early reminder that when the Pacific’s balance tips, the fallout rarely stays in the ocean.

This year’s version is still taking shape, but the direction is clear enough to worry forecasters. There is an 80 per cent chance of an El Niño developing by September. Most models forecast a moderate event. Yet some forecasts go further. hinting it could be very strong—sometimes described in headlines as a “super El Niño.”.

Even that worst-case label doesn’t do the most unsettling part justice. The deeper concern is what comes after this episode: more damaging El Niños are expected in the coming decades. and the reasoning isn’t just about how strong each event becomes. However strong this El Niño turns out to be. the next wave of impacts is expected to ride on a warmer world where the same phenomenon hits harder.

“Even a standard El Niño event in future will cause larger regional and global impacts,” says Axel Timmermann at Pusan National University in South Korea.

What makes researchers push harder is not only the possibility of a strong El Niño. but evidence that the climate system itself may start to behave differently. Studies by Timmermann and others suggest El Niño and La Niña—collectively known as ENSO events—could grow stronger and begin driving weather in the Atlantic as well. amplifying their impacts.

“Our latest computer model simulations predict a shift to more regular and much stronger El Niño-La Niña extremes, as well as an intensification of ENSO impacts on remote regions, in particular Europe,” Timmermann says.

The mechanics start in the Pacific. Under so-called neutral conditions, trade winds blow westwards along the equator. They shove surface water to the western Pacific, piling warm water there. Cold water wells up next to South America to replace what’s being pushed away. Warm, moist air rises above the warm water, producing heavy rainfall.

El Niño begins when the trade winds weaken and sometimes reverse. Warm water then spills eastwards, and the rainfall shifts east with it. That change can strengthen easterly winds, part of the feedback loops that help El Niños develop. The consequences spread outward from there: droughts can hit places such as Australia and Indonesia. while floods can strike South America.

The phenomenon also pushes heat into the atmosphere quickly. With a larger area of warm water, evaporation increases. Energy is released as latent heat when clouds form, transferring vast amounts of heat from the Pacific into the atmosphere.

How strong an El Niño is can be tracked through sea-surface temperature. Definitions vary, but an El Niño is said to be happening when the sea-surface temperature anomaly exceeds 0.5°C. A super El Niño isn’t a scientific term. but some scientists suggest it could be used for events above 2°C. Adam Scaife at the Met Office Hadley Centre in the UK suggests “Godzilla El Niño” could refer to events above 3°C.

But El Niño doesn’t simply accelerate without limits. As events develop, negative feedback loops start to work. More clouds over the central Pacific have a cooling effect. That can pull the system back toward neutral conditions or shift it into La Niña. when westerly trade winds strengthen and push cooler upwelling water further west than usual.

The scale of disruption in the past is part of why current forecasts feel so heavy. The three strongest El Niños since records began were in 1982-83, 1997-98 and 2015-16. All three caused immense damage to people and wildlife, including mass die-offs of corals and other marine life.

The financial toll has been just as stark. Each super El Niño caused trillions of dollars in damages. according to a 2023 study by Christopher Callahan at Indiana University. “Our results show that the magnitude of the economic loss is directly related to the strength of the temperature of the ocean in the Pacific. ” Callahan says. “If there is a significant El Niño this year. we should expect trillions in economic losses similar to previous events.”.

Callahan’s warning lands in a wider context that many researchers say is unavoidable: as the planet warms, future El Niños—and super El Niños—are expected to do even more damage.

“The science is very clear,” says Richard Allan at the University of Reading, UK.

Allan points to two kinds of consequences that show up again and again in a warmer atmosphere. ENSO-related floods will become more intense because there will be more moisture in the atmosphere. meaning more rain falls when it rains. Droughts will last longer and become more intense too, because soils dry out faster when it is hotter.

Some climate models also suggest warming could amplify the feedback loops that drive ENSO events. That could mean stronger El Niños and La Niñas, along with faster transitions between them—greater “climate whiplash”—making it harder for societies to prepare.

“It would mean much larger swings between years with larger-than-normal rainfall and years with drought in many regions of the world,” says Malte Stuecker at the University of Hawaiʻi, a member of Timmermann’s team.

Then comes the most uncomfortable twist: a team’s study suggests these stronger swings could lead ENSO events to start driving and synchronising with the North Atlantic oscillation. If that happens, Europe could be caught in the middle of bigger swings between floods and droughts.

“This would be a big regime shift for Europe, as in the current climate, we do not see a large impact of El Niño on weather patterns in Europe,” Stuecker says.

There is agreement on at least one point: higher certainty that El Niños of the same magnitude will be more damaging. Beyond that, the future is messier. Scaife says there is “quite a bit of disagreement about the future behaviour of El Niño and La Niña.” Some climate models do not project an intensification of El Niño. while many still agree on closer links with regions such as the Atlantic—suggesting ENSO impacts beyond the Pacific are likely to get even stronger.

Even if ENSO events become more intense, they won’t keep intensifying forever, Timmermann warns. The intensification is driven in part by the rapid warming of the top 100 metres of water in much of the Pacific. Once deeper waters begin to catch up and the temperature difference falls, ENSO events are likely to weaken.

The catch is timing. Timmermann says this weakening might not start to happen until after 2150.

So the calendar question—what kind of El Niño arrives by September—sits inside a much larger one. The next event may be ominous, but the real fear is how the system that produces it could change, year after year, as heat keeps building in the ocean and the sky responds.

El Niño ENSO La Niña climate change extreme weather Atlantic oscillation Europe drought floods sea surface temperature anomaly Godzilla El Niño super El Niño