Ocean temperatures on Earth hit record highs in 2025, and there is no stop in sight.

The majority of the planet's excess heat ends up in the ocean, but air temperatures make headlines. There, it can persist for decades, subtly influencing marine ecosystems, weather extremes, and sea levels. The amount of energy absorbed by the ocean is revealed by a recent worldwide investigation.

The world's seas stored more heat in 2025 than in any other year since the start of current observations, continuing a long-term increase that shows how much the Earth system is still warming.

The assessment calculates that the ocean accumulated over 23 petajoules of heat in 2025 using several independent datasets and contributions from over 50 scientists. This quantity of energy is equivalent to decades of worldwide human energy use.

Seas continue to rise, storms intensify, and the effects of climate change are becoming more difficult to deny, all of which can be attributed to this hidden heat.

A more distinct indication of warming

More than 90% of the extra heat that greenhouse gases trap is absorbed by the ocean. Ocean heat content is therefore one of the most accurate indicators of long-term warming. In essence, it is the planet's

The temperature of the air can fluctuate annually. El Niño may cause it to rise. It can be pulled down by La Niña. However, the heat content of the ocean is less erratic. It indicates that the Earth system is still gaining heat overall when it rises.

This conclusion was not predicated on data from a single group. To cross-check the findings, the researchers integrated an ocean reanalysis from CIGAR-RT with three observational products from the Chinese Academy of Sciences, the Copernicus Marine Service, and NOAA/NCEI.

All of the observations indicated that the ocean's heat content reached its greatest level ever in 2025. The ocean has hit a new record high in each of the previous nine years, so it's part of a pattern.

Hot locations across the world

Weather patterns and maritime consequences are shaped by the uneven warming of different sections of the ocean. Approximately 16% of the world's ocean area experienced record-high temperatures in 2025. among their local records, about 33 percent were among the top three warmest figures.

The North Pacific, the Southern Ocean, and the tropical and South Atlantic were the hottest regions. According to the study, trends in ocean warming have been more pronounced since the 1990s than in previous decades. The heat increase in the higher 6,560 feet (2,000 meters) has been consistent for some time, while there are indications that the rate has somewhat increased.

Heat travels beneath the surface.

The sea-surface temperature in 2025 was around 0.9 °F (0.5 °C) higher than the average from 1981 to 2010, making it the third warmest year in the instrumental record. Because of the tropical Pacific's shift from El Niño to La Niña, it was somewhat lower than in 2023 and 2024.

The ocean heat record is not contradicted by that. While the total amount of heat stored in the ocean continues to rise, surface temperatures may somewhat decrease as heat shifts both vertically and regionally.

Because it promotes evaporation, surface temperature is still important. Increased evaporation increases atmospheric moisture, which can result in higher rainfall and more powerful tropical cyclones during storm formation.

According to the analysis, significant disruptions in 2025, such as extensive flooding throughout much of Southeast Asia, are linked to hotter waters. flooding in Mexico and the Pacific Northwest, and drought in the Middle East.

The effects of ocean heat on humans

There are several significant downstream implications of increased ocean warming. First, thermal expansion causes the water level to rise. Seas rise even in the absence of glacier meltwater because warmer water occupies more area.

Secondly, it can exacerbate extremes. Heat and moisture from a warmer ocean can enter the atmosphere, intensifying periods of heavy rain and giving some storms extra power. By maintaining a warmer background environment, it can potentially prolong heatwaves.

The unsettling conclusion is simple: ocean heat content will continue to rise as long as the globe continues to accumulate heat. This implies that records will continue to decline.

Ocean warming's effects

The journal is putting together a special collection on changes in ocean heat content, which includes research on regional trends and causes in areas such as the Indian Ocean, the South Pacific, and the seas surrounding China.

Lijing Cheng, the corresponding author of the paper, proposed cartoon figures for the cover, including a crab and a dejected prawn. "The concept originates from the 'shrimp soldiers and crab generals' defending the underwater palace in Journey to the West," Cheng explained.

"We reimagined them as vulnerable creatures whose armor—their shells and scales—is under attack by ocean warming, acidification, and other ocean environmental changes, rather than as powerful guardians."

It's a minor detail, but it makes the point. There is more to the ocean heat record than just a graph. It puts strain on coasts, ecosystems, and the weather that affects people where they reside.