In 2025, Earth’s oceans quietly broke another heat record—fueling a hotter, more extreme future.
A global team of scientists reports that Earth’s oceans absorbed more heat in 2025 than in any year since modern observations began. The findings, published today (January 9) in Advances in Atmospheric Sciences, show that ocean heat content reached an unprecedented level, continuing a long-term warming trend.
In total, the ocean gained 23 Zetta Joules (23,000,000,000,000,000,000,000 Joules of energy) of heat in 2025. That amount of energy is roughly equal to about 37 years of global primary energy use at 2023 consumption rates (~620 Exa Joules per year). The analysis reflects the work of more than 50 researchers from 31 institutions around the world, making it one of the most comprehensive assessments of ocean heat to date.
Why the Oceans Matter for Climate
The ocean plays a central role in regulating Earth’s climate. More than 90% of the extra heat trapped by greenhouse gases ends up in the ocean, making it the planet’s largest heat storage system. Because ocean heat content (OHC) measures how much heat the ocean has accumulated over time, scientists consider it one of the most reliable indicators of long-term climate change.
How Scientists Measured the Heat
To assess ocean warming, researchers combined multiple independent data sources from major international centers. These included three observational products from the Institute of Atmospheric Physics at the Chinese Academy of Sciences, Copernicus Marine, and NOAA/NCEI, along with an ocean reanalysis known as CIGAR-RT. Together, these datasets span Asia, Europe, and America and provide a consistent picture of rising ocean heat.
All of the datasets confirm that ocean heat content reached its highest level on record in 2025, reinforcing evidence that the oceans continue to absorb increasing amounts of energy year after year.
Uneven Warming Across the Global Ocean
Ocean warming is not occurring at the same pace everywhere. In 2025, roughly 16% of the global ocean surface reached its highest heat content on record, while about 33% ranked among the three warmest years ever observed in those regions. The most pronounced warming occurred in the tropical oceans, the South Atlantic, the North Pacific, and the Southern Ocean.
Overall trends show that ocean warming has accelerated since the 1990s. Heat accumulation in the upper 2000m of the ocean has remained fairly steady in recent decades, although scientists detect a slight increase in the rate of warming. Notably, ocean heat content reached a new record in 2025, marking the ninth consecutive year in which a record was set.
Ocean Surface Temperatures and Weather Impacts
In 2025, global average sea surface temperature ranked as the third warmest year in the instrumental record. Temperatures remained about 0.5 °C (approximately 1°F) above the 1981–2010 average. Sea surface temperatures were slightly lower than in 2023 and 2024, largely due to a shift from El Niño to La Niña conditions in the tropical Pacific.
Surface ocean temperatures are especially important because they strongly influence weather patterns around the world. Warmer waters increase evaporation and intensify rainfall, contributing to stronger tropical cyclones and more extreme weather. In 2025, these conditions played a major role in severe flooding across much of Southeast Asia, prolonged drought in the Middle East, and flooding in parts of Mexico and the Pacific Northwest.
Why Rising Ocean Heat Is a Global Concern
As the ocean continues to warm, the impacts extend far beyond the water itself. Higher ocean heat contributes to rising sea levels through thermal expansion, increases the intensity and duration of heatwaves, and fuels more powerful storms by adding heat and moisture to the atmosphere. As long as Earth continues to gain energy, ocean heat content will keep rising and new records will continue to be set.
A Growing Body of Climate Research
The results will appear in a special collection on Ocean Heat Content Changes published by Advances in Atmospheric Sciences. The collection’s cover features cartoon images of a sad shrimp and crab, an idea suggested by the study’s corresponding author, Lijing Cheng of the Institute of Atmospheric Physics at the Chinese Academy of Sciences.
“The idea comes from the ‘shrimp soldiers and crab generals’ guarding the underwater palace in Journey to the West,” Cheng said. “We reimagined them not as mighty guardians, but as vulnerable creatures whose armor—their shells and scales—is under attack by ocean warming, acidification and other ocean environmental changes.”
The collection will explore multiple dimensions of ocean heat change, including detailed regional studies focused on waters around China, the South Pacific, and the Indian Ocean. As climate scientist Kevin Trenberth noted in the preface, the collection is designed to grow over time, reflecting ongoing advances in climate science.
The Choices Ahead
Although scientific understanding continues to evolve, one message remains consistent. The greatest uncertainty facing the climate is how humanity responds. By cutting emissions, preparing for future impacts, and acting collectively, it is still possible to protect a climate in which people and ecosystems can continue to thrive.
Reference: “Ocean Heat Content Sets Another Record in 2025” by Yuying Pan, Lijing Cheng, John Abraham, Kevin E. Trenberth, James Reagan, Juan Du, Zhankun Wang, Andrea Storto, Karina Von Schuckmann, Yujing Zhu, Michael E. Mann, Jiang Zhu, Fan Wang, Fujiang Yu, Ricardo Locarnini, John Fasullo, Boyin Huang, Garrett Graham, Xungang Yin, Viktor Gouretski, Fei Zheng, Yuanlong Li, Bin Zhang, Liying Wan, Xingrong Chen, Dakui Wang, Licheng Feng, Xiangzhou Song, Yulong Liu, Franco Reseghetti, Simona Simoncelli, Gengxin Chen, Rongwang Zhang, Alexey Mishonov, Wangxu Wei, Zhetao Tan, Guancheng Li, Lijuan Cao, Lifan Chen, Huifeng Yuan, Kewei Lyu, Albertus Sulaiman, Michael Mayer, Huizan Wang, Zhanhong Ma, Senliang Bao, Hengqian Yan, Zenghong Liu, Chunxue Yang, Xu Liu, Zeke Hausfather, Flora Gues, Xinyi Song, Miao Zhang and Lin Chen, 9 January 2026, Advances in Atmospheric Sciences.
DOI: 10.1007/s00376-026-5876-0
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7 Comments
Hotter climate? Europe is going through one of the snowiest winters in years – as it SHOULD – and these bozos still keep yapping about global warming.
Truly, global warming is a cult that cannot go wrong, is it? If it’s getting hotter, it’s because of global warming. If it’s getting colder, global warming. If it’s anything in between – global warming again.
That’s a level of delusion one can see in Christians and Trumpists.
” Higher ocean heat contributes to rising sea levels through thermal expansion,”
Love the outright lies published in these articles.
They keep saying this without a single example of it actually happening.
In fact there are hundreds of examples showing quite the contrary, that the ocean sea levels have not risen measurably at all.
Keep pushing that propaganda!
Also a little hilarious that the article next to this one on the main page is titled “Oceans Are Struggling To Absorb Carbon As Microplastics Flood Their Waters”
Is not carbon the big “heat absorber” these propagandists keep screaming about?
If the ocean is struggling to absorb carbon how is it continuing to heat up so fast?
“By cutting emissions, preparing for future impacts, and acting collectively, it is still possible to protect a climate in which people and ecosystems can continue to thrive.”
That’s a nice thought. It won’t happen because we humans can’t face the truth that we are vicious, vindictive, greedy and like to hate each other.
“The oceans soaked up a record-breaking amount of heat in 2025, storing energy equal to decades of human power use.”
How did the oceans store decades of equivalent anthropogenic heat in one year? Is it that the human contribution is small?
“Because ocean heat content (OHC) measures how much heat the ocean has accumulated over time, scientists consider it one of the most reliable indicators of long-term climate change.”
Is there an unstated assumption that once the oceans acquire heat that it never leaves? If not, then shouldn’t they mention that what is critical is the difference between the rate at heat energy is lost and the rate at which it is gained?
Is all that heat located in the upper ‘mixed zone’ above the thermocline? Just how does that work since infra-red is strongly absorbed and facilitates warming of the water surface, which makes it easier to evaporate water molecules, which then cools the surface?
“Sea surface temperatures were slightly lower than in 2023 and 2024, largely due to a shift from El Niño to La Niña conditions in the tropical Pacific.”
So what does that mean? If anthropogenic CO2 is responsible for the warming, does that mean that anthro’ CO2 declined in 2025. What causes the oscillation between El Niño and La Niña conditions? Where does the heat energy to warm the El Niño water come from? After all, heat conducts FROM a warmer body TO a cooler body.
” Higher ocean heat …, increases the intensity and duration of heatwaves, …”
Just how does that work since heat can’t be transferred by conduction from a relatively cool ocean to a hot terrestrial interior?
I would appreciate these experts explaining just how the things that they are claiming to be happening to actually be happening. As it is, the way these press releases are written, we are expected to believe, without evidence, that they are happening the way claimed. There is an old saying that one doesn’t really understand something until they can explain in a way that everyone can understand. It is often a rude awakening for a new teacher to discover that they don’t understand something as well as they thought when they have to explain it for the first time. Personally, I’m uncomfortable accepting, at face value, claims made by someone without support or explanation. Without explanation, assertions are little better than propaganda. These experts are missing out on an opportunity to demonstrate just how well they understand climatology and the principles of physics. I would welcome the opportunity to be educated, rather than be lectured.
“…, vulnerable creatures whose armor—their shells and scales—is under attack by ocean warming, acidification and other ocean environmental changes.”
For the record, many calcifiers protect their shells with chitin and mucous to protect them from the Universal Solvent — water. Creatures like crabs have shells made entirely of chitin. It is a misnomer to speak of “acidification” because the ocean is not, and never will be acidic because of (bi)carbonate/buffering. Even over volcanic CO2 emissions such as are found in Indonesia, where the water is saturated with CO2, the water does not reach a pH of 7 — neutrality.
How far back do these records go? No mention of when they started.