Oceans recorded their highest annual heat gain in 2025.

A 2025 study published in Advances in Atmospheric Science found the world's oceans absorbed an additional 23 zettajoules of heat, the largest annual increase since modern measurements began, and the eighth consecutive year of rising ocean heat content.

The world's oceans absorbed a record amount of heat in 2025, according to a multi-author study published in Advances in Atmospheric Science. Researchers calculated an additional 23 zettajoules of ocean heat that year, the largest annual increase since modern measurements began in the 1960s. This result continues a run of yearly increases in ocean heat content observed over the past eight years. The study involved more than 50 scientists across the United States, Europe, and China. Key findings: - The study reports an added 23 zettajoules of heat absorbed by the oceans in 2025, compared with 16 zettajoules in 2024. - This is the eighth straight year of rising global ocean heat content in the researchers' record. - The oceans absorb more than 90 percent of excess warming trapped in the atmosphere, with much of that heat moving from the surface into deeper layers through circulation and currents. - Sea surface temperatures in 2025 were slightly lower than in 2024, a difference the study links in part to a weak La Niña developing at the end of 2025 versus a strong El Niño in 2024. Summary: The new measurements underscore that the oceans continue to store growing amounts of excess heat, which is distributed through both surface and deeper ocean layers. Undetermined at this time.