The Guardian reports on the tenth Copernicus ocean state report, published by Mercator Ocean International, that the world’s oceans absorbed a record 23 zettajoules of heat in 2025 — almost forty times the total energy humanity used that year. The coverage notes that the oceans take in roughly 90 percent of the excess heat trapped by greenhouse gases.
The report also indicates mean sea-level rise averaged 4.2 millimetres per year over 2012–2025. It describes combined pressures from warming, rising seas and acidification on marine ecosystems.
Between January 2023 and September 2025, the Copernicus report found 84 percent of coral reefs experienced heat stress at levels associated with bleaching. That measure describes exposure to heat stress, not the proportion of reefs that died.
