Oceans Absorbed 37 Years of Human Energy Use in a Single Year

Beneath waves that looked normal, the world’s oceans quietly broke their heat record again in 2025.

An international team of more than 50 scientists confirmed the upper 2,000 meters of seawater absorbed an additional 23 zetta joules compared with the previous year. That figure is roughly equivalent to 37 years of global energy consumption packed into twelve months. The findings, published January 9 in Advances in Atmospheric Sciences, mark the ninth consecutive year ocean heat content has reached a new high.

The oceans function as a massive thermal savings account for the climate system. More than 90 percent of the excess heat trapped by greenhouse gases ends up in seawater rather than the atmosphere. Without this buffer, air temperatures would be climbing far faster. Ocean heat content captures that accumulation over time, smoothing out short-term weather swings and revealing where the climate is actually headed.

A Cooling Surface Hid What Was Happening Below

Global sea surface temperatures in 2025 ranked third warmest on record, about half a degree Celsius above the 1981 to 2010 average. The tropical Pacific had shifted from El Niño toward La Niña, a natural cooling phase that typically tempers global temperatures. At the surface, things looked slightly calmer than the record peaks of 2023 and 2024.

The deeper waters told a different story. Cooler surface conditions can actually allow the ocean to absorb energy more efficiently, pushing heat downward rather than releasing it back into the air. About 16 percent of the global ocean reached its highest heat content ever measured. Roughly one third ranked among the three warmest values in local records. The strongest warming appeared in the tropical and South Atlantic, the North Pacific, and the Southern Ocean, with elevated temperatures extending hundreds to thousands of meters deep.

This accumulation is doing more than warming water. Thermal expansion drives sea levels higher as heated water physically takes up more space. The stored energy fuels longer marine heatwaves and loads the atmosphere with extra moisture. In 2025, warmer ocean surfaces contributed to catastrophic flooding in Southeast Asia and Mexico while simultaneously intensifying droughts in the Middle East. The rate of ocean warming has increased significantly since the 1990s.

In Palawan, Philippines, researchers have documented bleached coral reefs that now resemble ghost towns of white calcium.

The Creatures Losing Their Armor

The study’s cover image drew on mythical shrimp soldiers and crab generals from Journey to the West, reimagining them not as mighty guardians but as vulnerable creatures under siege.

“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,” Lijing Cheng explains.

Cheng, the study’s corresponding author at the Institute of Atmospheric Physics of the Chinese Academy of Sciences, notes the metaphor is playful but the implications are serious. Rising heat and increasing acidity are weakening the calcium carbonate structures that shellfish and corals depend on. These ecosystems were already stressed. The compounding pressures make recovery harder with each passing year.

The authors are direct about what the data means going forward. As long as Earth traps more energy than it releases, ocean heat content will keep climbing and records will keep falling. The most significant variable in climate projections is not the water itself but decisions made on land to curb emissions. The oceans have been absorbing consequences for decades now. That capacity is not infinite, and 2025 suggests the buffer is being tested closer to its limits than ever before.

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