Global ocean temperatures climbed to a record high in June, with average sea surface temperatures reaching 20.98°C.
As scientists warned that the combination of climate change and a developing El Niño could push the planet into another period of exceptional warmth. According to the European Union’s Copernicus Marine Service, June 2026 was the hottest June ever recorded for the world’s oceans, surpassing the previous highs set in 2023 and 2024.
The record capped an exceptionally warm first half of the year, during which the global average sea surface temperature stood at 20.04°C, just below the record set over the same period in 2024. Scientists said the sustained ocean warmth reflects the growing impact of human-induced climate change and could intensify further as El Niño strengthens.
Carlo Buontempo, Director of the Copernicus Climate Change Service, said current conditions may signal the beginning of another period of unprecedented ocean warming. With sea temperatures already at record levels and El Niño expected to develop further, scientists believe additional global temperature records could be broken in the coming months.
El Niño expected to amplify global heat
El Niño is a naturally occurring climate pattern characterised by unusually warm waters in parts of the Pacific Ocean. The phenomenon releases additional heat into the atmosphere and alters global weather patterns, increasing the likelihood of floods, droughts, heatwaves and wildfires in different parts of the world.
Scientists said the expected El Niño will add to the long-term warming caused by greenhouse gas emissions, making 2026 one of the warmest years on record.
Oceans face growing climate stress
The latest findings come shortly after a major UN scientific assessment warned that the world’s oceans are in a “deepening crisis”, with warming and sea-level rise accelerating.
The oceans absorb nearly 90% of the excess heat generated by greenhouse gas emissions, helping regulate Earth’s climate. However, rising sea temperatures also fuel stronger tropical cyclones, heavier rainfall, rising sea levels and widespread coral bleaching during prolonged marine heatwaves.
Marine heatwaves affect vast areas
Between January and June, marine heatwaves affected around 82% of the world’s oceans, marking the second-largest extent ever observed after 2024.
The Mediterranean Sea recorded its warmest June on record at 24.3°C, while marine heatwaves covered almost 98% of the basin during the first six months of the year. Separately, a marine heatwave in the northwestern Mediterranean reached record intensity after Europe experienced an intense spell of extreme heat.
The tropical Pacific Ocean also posted its hottest June on record, with an average sea surface temperature of 27.26°C. Scientists observed the strongest warming in the western equatorial Pacific and off the coasts of Peru and California, reinforcing expectations that El Niño will continue to strengthen in the months ahead.
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