Average ocean temperatures hit a record 21.10 degrees Celsius (69.98 degrees Fahrenheit) on August 22, according to the European Union’s Copernicus Climate Change Service (C3S).
That’s not as hot as a warm bath, but it is the hottest the world’s oceans have been since C3S started keeping records in 1979.
“As a climate scientist, this is not surprising to me all,” says Zachary Labe, a climate scientist at Climate Central, a climate research nonprofit. “It’s consistent with decades of research showing how our climate is changing as the planet warms. And without reductions in the burning of fossil fuels, this warming will only continue.”
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The previous high, with a temperature of 21.09 degrees C (69.96 degrees F), occurred in March 2024, C3S said in a statement.
The daily average sea-surface temperature in 2024 (yellow), 2025 (orange) and 2026 (red). The 1991–2020 daily average appears as a dashed gray line.
ERA5/C3S/ECMWF
The new high also reflects the fact that we are heading into an exceptionally strong El Niño year. This cyclic climate pattern is marked by unusually hot Pacific Ocean temperatures, which can affect the entire planet’s weather.
“This record is another clear signal of an ocean under growing stress,” said Samantha Burgess, strategic lead for climate at the European Center for Medium-Range Weather Forecasts (ECMWF), in the same statement.
Hotter ocean temperatures can worsen sea-level rise, disrupt weather patterns and pose dangers to sea life such as coral reefs, Labe says. “These changes can affect nearly every part of society, including the economy, coastal infrastructure and global security.”
The new record is unlikely to last long, he adds. “This won’t be the last time we say this, and unfortunately, it’s very possible we could break this record again in the coming months,” Labe says.