Oceans absorbed record heat equal to 40 times annual global energy use

A global ocean analysis reports that 23 zettajoules of heat were absorbed by the seas in a single year - almost 40 times the total energy humanity used that year - driving measurable warming, rising seas and increased acidification. Sea levels have climbed about 3.8 mm per year since 1999 and 4.2 mm per year between 2012 and 2025, while average ocean acidity has increased by roughly 17% over the past 40 years. Oceans continue to take up about one-third of emitted CO2 and roughly 90% of excess heat trapped by greenhouse gases. Regional details highlight Europe warming twice as fast as the global average: the Mediterranean has warmed by about 0.32°C per decade, experienced record deep and prolonged marine heatwaves, and shows accelerating western sea-level rise.

The heating is already reshaping ecosystems and human health: between January 2023 and September 2025, 84% of coral reefs experienced bleaching-level heat stress; nearly 5% of the ocean has undergone persistent shifts in phytoplankton growth patterns over 30 years; and four Antarctic emperor penguin colonies failed to breed in 2022 amid record low sea ice. Concurrent analysis shows an “ozone‑climate penalty,” with dangerous ground-level ozone during 2026 exposing more than one-third of people and only 5% of the global population experiencing WHO‑recommended ozone levels in the first eight months of the year.