WASHINGTON, DC, United States (AFP) — This year’s El Niño is on track to be the strongest on record, threatening to unleash extreme weather across the globe and make 2027 the hottest recorded year by far.

It is expected to be the most “intense” El Niño in more than a century, the United Kingdom’s Met Office warned last Friday.

Stacked on top of long-term, human-caused climate change, the temporary jolt will offer a glimpse of the heat the world can expect by the late 2030s, experts say.

Here’s what to know:

What is El Niño?

El Niño is the warming phase of a natural cycle in the tropical Pacific known as the El Niño-Southern Oscillation (ENSO).

It sets in when trade winds that blow from east to west temporarily ease up, allowing warm water which normally piles up in the western Pacific Ocean to slide back east and rise to the surface.

When those warmer-than-average surface temperatures last for a few months they cause more storms and clouds over the region “which cause ripple effects through the entire global atmosphere”, explained Emily Becker, a University of Miami climate scientist.

The upshot is hotter and drier conditions in some places, cooler and wetter in others.

Some effects are already being felt. For example, Indonesia’s long, intense dry season has fed wildfires that have burned hundreds of thousands of hectares.

“Stronger events mean that we can expect to see more of these expected El Niño impacts,” Michelle L’Heureux, ENSO team lead at the National Oceanic and Atmospheric Administration (NOAA)’s Climate Prediction Center, told AFP, though she cautioned none are guaranteed.

What’s going on this year?

Daily sea surface temperatures in the Nino 3.4 region — an imaginary box in the Pacific — are currently running about 2.6C above a rolling 30-year-average, according to the highly cited Climate Brink dashboard, which draws on NOAA’s satellite-and-buoy sea surface record.

The dashboard also aggregates forecasts that put El Niño on course to peak at a 3.9°C anomaly this November — well above the 3°C anomaly detected in the 2015 El Niño.

It stands to make this year a contender for the hottest year on record, currently held by 2024, and make 2027 a near certainty for top spot since most of the heat impact will be felt the following year.

According to calculations by climate scientists Zeke Hausfather and Andrew Dessler, El Niño will add a temporary 0.3°C on top of the long-term global warming trend, resulting in a 2027 temperature of 1.76°C above pre-industrial levels — compressing into a single year as much warming as would otherwise be expected by 2037.

“It’s kind of a preview of the future,” Dessler, a professor at Texas A&M told
AFP, though much of that heat will be focused in the equatorial Pacific.

Mike McPhaden, a senior scientist at NOAA’s Pacific Marine Environmental Laboratory, had a similar estimate, telling
AFP: “It’s not inconceivable that 2027 may top out at 1.7°C above pre-industrial levels” if model forecasts bear out.

There is not one single accepted way to measure El Niños.

NOAA in February adopted the Relative Oceanic Nino Index (RONI), which gauges warming in the Nino 3.4 region against warming across the whole tropical belt to try to better represent the ocean-atmosphere system driving ENSO impacts.

On that scale, the numbers run lower but the predicted ranking remains the same: NOAA puts the odds at 69 per cent that this El Niño will be the strongest in its data set going back to 1950.

How climate change fits in

Scientists agree climate change increases El Niño’s impacts.

Our greenhouse gas-warmed atmosphere holds more moisture so El Niño-linked rains can turn more extreme. It also dries out soils, deepening drought where El Niño brings drought.

There is less consensus on whether climate change itself triggers stronger El Niños, though evidence for this is emerging.

“Climate change may be amplifying the El Niño cycle itself,” said NOAA’s McPhaden.

Warmer tropical seas make the winds that drive El Niño more responsive to the ocean, tightening the feedback between the two and letting events build faster, he explained.

McPhaden cited evidence from the paleo-record — for example coral skeletons — instrument readings that stretch back to the 19th century, and climate modelling which suggest El Niños may have increased in amplitude by about 10 per cent over the past century.

Infographic with a globe centred on the Pacific Ccean, showing surface temperature anomalies in July 2026 compared with the reference period 1991-2020, according to ERA5 data published by Copernicus (Graphic: AFP)