The world's oceans absorbed a record 23 zettajoules of additional heat in 2025, almost 40 times the energy humanity used that year, according to the 10th Copernicus Ocean State Report. Produced by Mercator Ocean International with contributions from more than 100 scientists, the report was published on 30 September.
It was the ninth consecutive year of record ocean heat accumulation, and the overall rate of ocean warming has doubled over the past 20 years. Global sea levels rose by 3.8mm a year between 1999 and 2025, accelerating to 4.2mm a year between 2012 and 2025, while the ocean became roughly 17% more acidic between 1985 and 2025 as it absorbed carbon dioxide.
