EU climate monitor warns oceans near record highs as El Niño takes shape

The European Union's climate monitor said that ocean temperatures are edging toward record highs as conditions shift toward a potentially powerful El Niño weather pattern.

Samantha Burgess from the European Centre for Medium-Range Weather Forecasts (ECMWF) said sea surface temperatures in recent days were just shy of the all-time highs of 2024 – and May looked set to break its own record.

"It's a matter of days before we are back to record-breaking ocean SSTs (sea surface temperatures) again," Burgess, strategic lead for climate at ECMWF, said.

The Copernicus Climate Change Service said daily sea surface temperatures in April "gradually inched" toward near-record highs, reflecting the transition to El Niño expected in coming months.

Record-breaking marine heatwaves

Copernicus, which is overseen by the ECMWF, said sea surface temperatures in April were the second-highest measured, with marine heatwaves breaking records in the ocean between the tropical Pacific and the United States.

Last month, the World Meteorological Organization said El Niño conditions could develop as soon as May to July.

One phase of a natural climate cycle in Pacific Ocean temperatures and trade winds, El Niño influences global weather and increases the likelihood of drought, heavy rainfall and other climate extremes.

It also adds heat to a planet already warmed from burning fossil fuels. The last El Niño helped make 2023 and 2024 the second- and first-hottest years on record, respectively.

Some weather agencies forecast the coming event will be even stronger – possibly rivaling a "super" El Niño three decades ago.

Zeke Hausfather, a scientist at Berkeley Earth, an independent climate research organization, wrote last week that a strong El Niño could significantly raise the chances of 2027 becoming the hottest year ever recorded.

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Burgess said it was still too early to predict the event's intensity with confidence as forecasts made during the Northern Hemisphere spring could be unreliable.

But she said regardless of its strength, this El Niño would not go unnoticed.

"We're likely to see 2027 exceed 2024 for the warmest year on record," she said. El Niño's impact on global temperatures typically comes the year after its peak, she added.

Copernicus said the upturn in ocean temperatures over March and April indicated the transition from neutral conditions to El Niño was underway.

Scientists stress that El Niño alone is not driving the extraordinary ocean warmth or its knock-on effects, such as coral bleaching and marine heatwaves.

The phenomenon is unfolding against a backdrop of long-term global warming caused primarily by greenhouse gas emissions, with oceans absorbing around 90% of the excess heat generated by human activity.

In its monthly bulletin, Copernicus said April was the third-hottest globally and 1.43C above the 1850-1900 pre-industrial benchmark.

Arctic sea ice remained near record lows in April while Europe endured varied conditions that set the stage for a hotter and drier summer at risk of drought or wildfires, it said.

"We just keep seeing extremes. Every month we have more data that the climate change impact is creating these extreme events," said Burgess.