The world’s oceans absorbed a record 23 zettajoules of heat in 2025, according to a new Copernicus Ocean State Report released on September 30. It is the ninth record year in a row. The report says the rate of ocean warming has doubled in just 20 years, making the oceans a far more powerful engine of climate change.

The energy added in a single year equals about 12 atomic bombs’ worth of heat every second. Researchers say the warmer seas are already driving more severe storms, faster sea-level rise, and long marine heatwaves that damage coral reefs and fish stocks. Sea-surface temperatures set new records in 2023, 2024, and again in 2026.

The report links the surge partly to the strongest El Nino event ever recorded, which ended recently. Arctic sea ice also hit a record September low. “We are witnessing a record warm ocean,” said Copernicus scientist Karina von Schuckmann. Scientists warn that without deep cuts in greenhouse gas emissions, the trend will continue, raising risks for coastal cities and food systems worldwide.