Overview
- More than 50 scientists from 31 institutions synthesized multiple datasets, including products from IAP/CAS, Copernicus Marine, NOAA/NCEI, and the CIGAR-RT ocean reanalysis.
- About 16% of the global ocean reached record-high heat content in 2025 and roughly 33% ranked among their top three warmest, with notable hotspots in the tropical and South Atlantic, the North Pacific, and the Southern Ocean.
- Global average sea-surface temperature in 2025 ranked third warmest on record at about 0.5°C above the 1981–2010 baseline, dipping slightly from 2023–2024 with the shift from El Niño to La Niña.
- Rising ocean heat is driving sea-level rise through thermal expansion, fueling heavier rainfall and stronger tropical cyclones, and intensifying marine heatwaves that damage coral reefs and disrupt ecosystems.
- The upper 2,000 meters set a new high for the ninth consecutive year, reflecting a persistent planetary energy imbalance that scientists say will continue without sharp cuts in greenhouse-gas emissions.