The world must prepare for the imminent return of El Niño and the supercharged weather extremes it brings, the UN has warned.
The powerful natural weather pattern, which raises global temperatures and worsens some rainfall, has an 80% chance of forming before September and a 90% chance before November, the World Meteorological Organization (WMO) said on Tuesday.
It found most models projected the return of the cyclical phenomenon in the ocean and atmosphere to be “at least moderate” in strength, and possibly strong.
Scientists have previously warned that it could be the strongest this century. However, the WMO stopped short of backing such projections and said forecasters were still in a window of uncertainty.
“The spread is large,” said Celeste Saulo, the secretary general of the WMO. “There are models that are not providing any indication of a strong El Niño, while others are doing so.”
António Guterres, the UN secretary general, said the world “must treat it as the urgent climate warning it is”.
“El Niño conditions will pour fuel on the fire of a warming world,” he said. “Impacts will hit even harder, travel even farther, and cross borders with devastating speed.”
The most recent El Niño, which hit in 2023-24, was one of the five strongest on record and contributed to a scorchingly hot year in 2024 that broke global temperature records.
The WMO said unusually high temperatures were forecast in nearly all parts of the planet for the next three months, and warned of a greater probability of extreme rain and drought.
Although each El Niño event is unique, scientists usually associate them with heavier rain in parts of South America, the southern US, the Horn of Africa and central Asia. Drier conditions typically hit Central America, northern South America, the Caribbean, Australia, Indonesia and parts of south Asia.
The warm waters can fuel hurricanes in the central and eastern Pacific Ocean but hinder their formation in the Atlantic basin.
The finding comes as western Europe emerges from an unusually hot May in which temperature records for the month were broken in the UK and Ireland. Last week, the WMO and the UK Met Office warned that a record-breaking hot year for the globe was almost certain before the end of the decade, with the expected return of El Niño likely to make that come as soon as 2027.
Gareth Redmond-King, from the Energy & Climate Intelligence Unit, a British thinktank, said the findings were bad news for food supplies as they were already under strain from climate breakdown and the restriction of fertiliser flows from the Iran war.
“The havoc El Niño will wreak as it likely delivers another hottest year, in 2027, will be devastating for many farmers, and a question of life or death for far too many people,” he said.
El Niño conditions occur every few years and last around nine to 12 months. During such years, winds that push warm waters to the west soften or shift direction, enabling the surface waters in that part of the Pacific to warm.
The WMO said sea surface temperatures in parts of the Pacific that scientists use as a reference were approaching El Niño thresholds in late April to mid-May, fed by unusually warm subsurface conditions. It said the atmospheric component of El Niño was also consistent with its development.
It rejected the term “super El Niño”, which some scientists have used in recent months in anticipation of a particularly strong event, because it falls outside the official classification system.
Early-warning systems that alert people to danger and allow evacuations ahead of disasters have saved lives even as fossil fuel pollution has made extreme weather more violent. But in the last year, some major foreign donors that have helped pay for them, including the UK and US, have cut their aid budgets.
Saulo said: “Climate finance is not at its peak, I would say, but early-warning systems ha[ve] been and still [are] a priority. Of course, we still need more resource mobilisation, in terms of funding those countries that need the support. I would say we need to improve that, but that is not the only limit in this case. The implementation is also a challenge for the world.”
Guterres said: “The only effective response is climate action equal to the crisis – ending the addiction to fossil fuels, accelerating the shift to renewables, protecting the most vulnerable, and delivering early-warning systems for all.”