The last major El Niño event saw a string of heat records, and scientists fear warming seas signal more extreme weather to come.
This April was one of the hottest on record for both the land and the seas. With the world’s oceans heating up again, scientists say a powerful El Niño could push global temperatures even higher in the months to come.
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April 2026 saw the second-highest sea surface temperatures ever recorded for the extra-polar oceans, according to the EU’s Copernicus Climate Change Service.
Globally, April was also the joint third-warmest April on record, with average temperatures 1.43°C above pre-industrial levels – perilously close to the 1.5°C threshold set in 2015 under the Paris Agreement.
The findings add to growing concern that another period of extreme global heat may be on the horizon, with unusually warm oceans continuing to fuel climate extremes.
Why are sea temperatures rising again?
Sea surface temperatures are one of the clearest indicators of how much excess heat the planet is absorbing.
Copernicus data shows average sea surface temperatures across much of the global ocean reached 21°C in April – the second-highest level ever recorded for the month. Only April 2024, during the last major El Niño event, was hotter.
Parts of the tropical Pacific were especially warm, with record temperatures stretching from the central Pacific to the western coasts of the US and Mexico. Scientists described conditions there as “strong” marine heatwaves, a warning sign of the growing amount of heat building up in the planet’s oceans, largely due to human-driven climate change.
The world’s oceans have taken up more than 90 per cent of the excess heat trapped by greenhouse gas emissions since 1970, according to the Intergovernmental Panel on Climate Change. Hotter oceans can intensify storms, damage marine ecosystems and disrupt weather patterns around the world.
Samantha Burgess, strategic lead for climate at the European Centre for Medium-Range Weather Forecasts (ECMWF), said April’s data showed “a clear signal of sustained global warmth”.
“Sea surface temperatures were near record levels with widespread marine heatwaves, Arctic sea ice remained well below average, and Europe saw sharp contrasts in temperature and rainfall,” she said in a statement.
“All hallmarks of a climate increasingly shaped by extremes.”
What is a ‘super El Niño’?
Scientists are now watching closely for the possible arrival of a potentially devastating “super El Niño” later this year.
El Niño (Spanish for ‘the boy’) is a natural climate pattern triggered by unusually warm sea surface temperatures in the Pacific Ocean. It typically pushes global temperatures higher and can influence weather patterns worldwide, bringing droughts to some regions and floods to others.
Forecasts from the ECMWF suggest that ocean temperatures in the central Pacific near the equator could rise to as much as 3°C above average by autumn. If that happens, it will rank among the strongest El Niño events ever recorded.
Researchers generally classify a “super El Niño” as one where Pacific Ocean temperatures rise at least 2°C above average. However, the term isn’t formally used by the US National Oceanic and Atmospheric Administration (NOAA).
The last major El Niño event in 2024 helped drive a series of global heat records. Scientists fear another one, on top of a warming climate, could bring even more extreme weather.
Already in April, severe floods hit parts of the Arabian Peninsula, Iran and Afghanistan, while drought conditions worsened in southern Africa. Tropical cyclones also developed across the Pacific.
Europe sees a split in its climate picture
Europe experienced two very different Aprils last month. While Southwestern Europe saw much warmer than average conditions, with Spain recording its hottest April ever, Eastern Europe was cooler than normal.
The continent as a whole ended the month as only the tenth warmest April on record, but that figure masks these strong regional contrasts and recent trends.
A recent Copernicus report found that at least 95 per cent of Europe experienced above-average temperatures in 2025. The latest findings add to mounting evidence suggesting an accelerating climate crisis across the continent.
