Climate
Average sea surface temperature outside polar regions was 21.1C on Saturday, latest data finds
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Environment — Damian Carrington Environment editor
The world’s oceans were hotter than ever previously recorded on Saturday, according to the latest data.
The average surface temperature was 21.1C, with the rising marine heat a stark indicator of the climate crisis. More than 90% of the heat trapped by carbon dioxide from fossil fuel burning enters the oceans.
Hotter oceans exacerbate the sea level rise and extreme storms that threaten billions of people, as well as driving marine heatwaves that decimate sea life and undermine coastal livelihoods, scientists warned.
The northern hemisphere summer has already been hit by record-breaking heatwaves , drought and wildfires in Europe and North America , and intense rain and typhoons in Asia .
The ocean heat spike is being intensified by a fast developing El Niño event , which is set to be the hottest in at least a century. El Niño events are natural climate variations that raise global temperature and change weather patterns, with serious impacts around the world. The new El Niño has already delivered low monsoon rain in India , major wildfires in Indonesia and heightened fire concerns in Australia .
The new ocean heat record being set in August is especially remarkable as global sea temperatures are typically highest in March and April, after the austral summer. The southern hemisphere has significantly more ocean area than the northern.
“The record is another clear signal of an ocean under growing stress,” said Dr Samantha Burgess, at the European Union’s Copernicus Climate Change Service (C3S), which produced the new data. “El Niño is adding heat to the system, but it is doing so on top of decades of human-driven warming. The consequences are already visible: the number of marine heatwave days globally has more than tripled since the early 1990s.”
Warmer oceans contribute to sea level rise because of thermal expansion of the water, increasing flooding risks for coastal communities and low-lying island nations. Higher ocean temperatures also supercharge extreme weather events, because warmer seas transfer more energy and water vapour to the atmosphere, intensifying rainfall and storms.
Most of the planet-heating CO 2 from fossil fuel burning and forest destruction is absorbed by the oceans. However, a hotter ocean is less efficient at absorbing CO 2 . This is potentially weakening one of the planet’s most important natural buffers against global heating, the scientists said.
“Two key actions are needed to address this record ocean warming,” said Brian O’Donnell, director of Campaign for Nature. “Fossil fuel emissions need to be rapidly reduced. Meanwhile, it is essential that countries protect marine and coastal ecosystems. Kelp beds, mangroves and marshes absorb carbon and coral reefs protect against storms and provide habitat. More than 190 governments have committed to protect and conserve at least 30% of the planet by 2030, and now is the time to turn that commitment into effective, durable conservation on the ground.”
The data , from the C3S, covers the oceans outside the polar regions. The Arctic is the fastest-heating region on the planet. The records stretch back to 1979, when satellites began delivering the highest quality date.
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The average surface temperature was 21.1C, with the rising marine heat a stark indicator of the climate crisis. More than 90% of the heat trapped by carbon dioxide from fossil fuel burning enters the oceans.
This report is published with credit to The Guardian. Full available text from the wire is above. Read on The Guardian →
Source: The Guardian · Damian Carrington Environment editor. Published 24 Aug 2026, 12:49 pm.
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