The planet’s oceans have just logged their hottest June ever measured, and scientists say even more records could topple in the months ahead as El Niño builds on top of human-caused climate change.
In June, global average sea surface temperatures reached 20.98C, edging past the previous records set in 2023 and 2024, according to the European Union’s Copernicus Marine Service.
That milestone came at the end of six months of exceptional ocean heat in 2026, a stretch marked by stubborn marine heatwaves, the service said. Average sea temperatures over the first half of the year stood at 20.04C, just under the record posted during the same period in 2024.
Researchers also warned that the emergence of what could become a strong El Niño weather pattern may push heat levels in both the oceans and the atmosphere higher still through the rest of 2026 and into next year.
“With ocean temperatures at these levels and El Niño on the horizon, we are likely to see more temperature records fall in the coming months,” Dr Buontempo said in a statement.
Global average sea surface temperatures in June beat previous records
El Niño is defined by unusually warm waters across parts of the Pacific Ocean, which release added heat into the atmosphere and reshape wind, cloud and weather patterns worldwide.
Those shifts can heighten the chances of extreme weather, from flooding in Peru to drought in parts of Africa and wildfires in Australia.
It can also temporarily lift global temperatures, adding to the long-term warming driven by humanity’s continued use of fossil fuels.
Combined land and sea temperatures hit a record high in 2024 as the previous El Niño was fading.
“With the arrival and the onset of an El Niño year … we can expect that 2026 will be amongst the warmest (ever) recorded,” Simon Van Gennip, lead Oceanographer for the Copernicus Marine Service, said in a news briefing.
“This is due to El Niño … but also from the warming due to the greenhouse gas emissions we continue to provide for the atmosphere,” Dr Van Gennip said.
‘Deepening crisis’
The findings come after a major UN scientific assessment last month warned that the world’s oceans were in a “deepening crisis” as warming seas and rising water levels accelerated.
The oceans play a central role in regulating Earth’s climate, absorbing about 90% of the excess heat generated by human-produced greenhouse gases such as carbon dioxide.
As seas warm, they load more moisture into the atmosphere, creating conditions that can intensify tropical cyclones and unleash heavier, more destructive rainfall.
Hotter oceans also push sea levels higher because warming water expands, while prolonged marine heatwaves can create intolerable conditions for tropical reefs, leaving corals bleached and dead.
According to Copernicus Marine Service, the first six months of the year were dominated by widespread marine heatwaves affecting roughly 82% of the global ocean — the second-largest extent on record after 2024.
Marine heatwaves — extended periods of unusually high sea temperatures — can disrupt weather systems, trigger coral bleaching and kill marine wildlife.
Global heat
Sea surface temperatures did not rise evenly across the globe in the first half of the year, according to the service, which is operated by Mercator Ocean International, an EU-backed non-profit organisation.
The Mediterranean posted its hottest June on record at 24.3C, beating earlier highs reached in 2023 and 2025. During the first half of the year, marine heatwaves affected 98% of the basin.
A marine heatwave in the northwestern Mediterranean set a new record for intensity on Monday, according to a Spanish climate institute, after a week in which temperature records fell across Europe.
The tropical Pacific likewise recorded its warmest June ever at 27.26C.
Across the January-to-June period, the region matched its 2016 record, with the strongest and most sustained warming concentrated in the western equatorial Pacific and off the coasts of Peru and California.
