The average global sea surface temperature has reached a record high, according to the European Union's climate agency, which warns that the rapidly strengthening El Nino phenomenon and human-induced climate change are putting the oceans under "unprecedented stress."
The EU's Copernicus Climate Change Service reported that sea surface temperatures hit 21.1 degrees Celsius on Friday and Saturday, surpassing the previous record of 21.09 degrees Celsius set in March 2024.
"This record is yet another clear sign of an ocean under increasing strain," said Samantha Burgess, climate strategy lead at the European Centre for Medium-Range Weather Forecasts. "El Nino is adding heat to the system, but that is happening against a backdrop of decades of human-caused warming."
Copernicus called the timing of the new record "remarkable," as global ocean temperatures typically peak in March and April—when summer in the Southern Hemisphere, which is mostly ocean, comes to an end. But this year, the record was set in August.
Burgess told The Associated Press that oceans will continue to warm until El Nino—a natural, temporary warming of parts of the Pacific Ocean that alters weather and pushes global temperatures up—peaks, expected sometime between November and January.
The World Meteorological Organization also forecasts that El Nino will strengthen in the coming months, while Copernicus's seasonal forecasting system suggests the phenomenon "could reach levels not seen in decades."
The excess heat from El Nino comes on top of long-term warming from fossil fuels, which has already raised ocean temperatures by 0.8 degrees Celsius above pre-industrial levels, according to Burgess.
Copernicus warned that rising ocean temperatures have "far-reaching consequences" for marine ecosystems and coastal communities. Warmer oceans contribute to sea-level rise through thermal expansion and increase the likelihood and intensity of marine heatwaves, which can destroy coral reefs and seagrass meadows. This can disrupt food chains and threaten industries such as fishing and aquaculture.
Additionally, warmer oceans are less able to absorb carbon dioxide, weakening one of the planet's key shields against climate change. Higher ocean temperatures also provide extra heat and moisture to the atmosphere, increasing the potential for extreme weather events.
Jane Lubchenco, an oceanographer and former head of the U.S. National Oceanic and Atmospheric Administration, called the results "deeply concerning." "An ocean this warm destabilizes weather patterns and threatens food security, economic prosperity, and marine life," she told the AP. "A warmer ocean is not our friend."
