Oceans Took in the Equivalent of 37 Years of Worldwide Energy Use in Just One Year

Underneath waves that appeared ordinary, the oceans of our planet silently set a new heat record in 2025.

A global collaboration of over 50 researchers validated that the upper 2,000 meters of seawater captured an excess of 23 zetta joules compared to the year prior. This amount is approximately equal to 37 years’ worth of global energy use condensed into just one year. The results, released on January 9 in Advances in Atmospheric Sciences, signify the ninth consecutive year that ocean heat content has hit a peak.

The oceans serve as a colossal thermal reservoir for the climate system. Over 90 percent of the trapped heat from greenhouse gases is absorbed by seawater rather than being released into the atmosphere. Without this buffer, air temperatures would be rising at a much quicker pace. Ocean heat content reflects this buildup over time, mitigating short-term weather fluctuations and indicating the actual trajectory of the climate.

A Chilled Surface Concealed Underlying Changes

<pIn 2025, global sea surface temperatures ranked as the third hottest ever recorded, hovering approximately half a degree Celsius above the average from 1981 to 2010. The tropical Pacific exhibited a shift from El Niño to La Niña, a natural cooling occurrence that generally moderates global temperatures. At the surface level, conditions appeared somewhat tranquil compared to the record highs seen in 2023 and 2024.

However, deeper waters narrated a contrasting tale. Cooler conditions at the surface can enhance the ocean’s ability to absorb energy effectively, driving heat downward instead of releasing it into the atmosphere. Approximately 16 percent of the world’s oceans achieved their highest heat content ever recorded. About one third of these locations ranked among the three warmest readings in their local histories. The highest warming was detected in the tropical and South Atlantic, the North Pacific, and the Southern Ocean, with elevated temperatures reaching hundreds to thousands of meters below the surface.

This heat accumulation does more than raise water temperatures. Thermal expansion increases sea levels as heated water occupies more space. The stored energy contributes to prolonged marine heatwaves and adds moisture to the atmosphere. In 2025, higher ocean surface temperatures played a role in devastating floods in Southeast Asia and Mexico while simultaneously exacerbating drought conditions in the Middle East. The pace of ocean warming has markedly accelerated since the 1990s.

In Palawan, Philippines, scientists have recorded coral reefs that have bleached, resembling ghostly white calcium desolations.

The Beings Shedding Their Protection

The study’s cover art featured mythical shrimp warriors and crab leaders from Journey to the West, reimagined not as powerful protectors but as fragile beings under siege.

“We reimagined them not as powerful protectors, but as fragile beings whose armor, including their shells and scales, is threatened by ocean warming, acidification, and other environmental changes in the ocean,” explains Lijing Cheng.

Cheng, the lead author of the study from the Institute of Atmospheric Physics at the Chinese Academy of Sciences, emphasizes that while the metaphor is whimsical, the underlying issues are grave. The rising temperatures and increasing acidity are undermining the calcium carbonate frameworks essential for shellfish and corals. These ecosystems were already under stress, and the combined pressures complicate recovery each passing year.

The authors are candid about the implications of the data for the future. As long as the Earth retains more energy than it releases, ocean heat content will continue to rise, and records will keep breaking. The most crucial factor in climate forecasts is not the water itself but the choices made on land regarding emissions reductions. The oceans have borne these consequences for decades. This capacity is not limitless, and 2025 indicates that this buffer is being pushed closer to its boundaries than ever.

Advances in Atmospheric Sciences: 10.1007/s00376-026-5876-0