Overview
- The upper 2,000 meters of the global ocean gained an estimated 23 zettajoules of heat in 2025 compared with 2024, roughly equal to 37 years of 2023 global primary energy use.
- More than 50 scientists from 31 institutions combined multiple datasets from the Institute of Atmospheric Physics, Copernicus Marine, NOAA/NCEI, and an ocean reanalysis, drawing heavily on the Argo float network.
- About 16% of ocean area reached record-high heat content in 2025 and roughly 33% ranked among their top three warmest values, with hotspots in the tropical and South Atlantic, the North Pacific, and the Southern Ocean.
- Despite the deep-ocean record, global average sea-surface temperature in 2025 ranked third warmest on record at about 0.5°C above the 1981–2010 baseline, slightly cooler than 2023–2024 due to a shift from El Niño to La Niña.
- Scientists warn that continued ocean heating drives sea-level rise through thermal expansion, intensifies extreme rainfall and storms, and heightens stress on marine ecosystems including widespread coral bleaching.