Overview
- An international analysis published 9 January in Advances in Atmospheric Sciences reports an additional 23 zettajoules of heat stored in the upper 2,000 meters in 2025, the highest since modern records began.
- The assessment synthesizes three observational products and one reanalysis from 31 institutions, confirming continued ocean heat gain.
- Ocean warming is uneven: about 16% of waters reached record-high heat content and roughly 33% ranked among their top three, with hotspots in the tropical and South Atlantic, the North Pacific, and the Southern Ocean.
- The upper-ocean heat content has set new highs for nine consecutive years, with overall trends strengthening since the 1990s.
- Elevated ocean heat is driving thermal expansion and more volatile weather, with 2025 impacts linked to flooding in Southeast Asia, Mexico and the Pacific Northwest, and drought in the Middle East.