Ocean heat sets another record in 2025 as Earth sees third-hottest year
With 2025 deemed the third-warmest year on record for the planet, it comes as no surprise that ocean heat is also on the rise--setting a new record last year for the amount that was stored
With 2025 officially earmarked as third-warmest on record for global surface air temperatures, it's no surprise then that the sea surface temperature is following suit while also setting a record for heat storage.
A new study published in Advances in Atmospheric Sciences on Jan. 9 revealed that the ocean absorbed more heat in 2025 than in any year since modern measurements began.
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According to the examination, the upper 2,000 metres of ocean heat content increased by an estimated 23 zettajoules from 2024.
“The ocean is the hottest on record,” said Kevin Trenberth, an honorary academic at the University of Auckland and study co-author, in a news release. “We’re looking at creating a very different planet. Do we really want to do that?”
Leblon Beach in Rio de Janeiro, Brazil. (Getty Images/Brunomartinsimagens/2231648064-170667a)
Ocean warming not one-size fits all
While the ocean heat content has risen overall, the warming isn't the same across the board. Some oceans are warming up quicker than others.
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In 2025, about 16 per cent of the worldwide ocean area hit a record-high of ocean heat content (OHC), according to the study. It also revealed that approximately 33 per cent of the ocean area was ranked among the top three warmest values in its historical records (1958-2025). Around 57 per cent of it made the top five.
The warmest areas included the tropical, and South Atlantic and North Pacific oceans, and the North Indian and Southern oceans.
(Unsplash)
The oceans act like sponges when it comes to the heat confined by greenhouse gases, soaking up more than 90 per cent of the surplus amount--making it the primary pool of the climate system.
Because ocean heat content (OHC) reflects the accumulation of heat stored in the ocean, it provides one of the best indicators of long-term climate change.
Third-warmest sea surface temperature
The study also found the global annual mean sea surface temperature in 2025 ranked as the third hottest on record, reaching 0.49 C above the 1981–2010 baseline, slightly lower than in 2024 and 2023.
Despite the development of La Niña conditions, with the temperature reflecting them, 2025's value was still positioned in the third-highest spot.
“Sea surface temperatures were exceptionally high near and around New Zealand during December 2025 into January 2026 from La Niña and global warming,” said Trenberth. “There’s a link with our unstable, showery, recent weather.”
According to a Institute of Atmospheric Physics, Chinese Academy of Sciences news release, the high sea surface temperature in 2025 played a huge role in the widespread flooding and disruption across a large portion of southeastern Asia and drought in the Middle East, as well as flooding in Mexico and the Pacific Northwest.
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