World’s seas heated by a record 23 zettajoules last year
The injection of thermal energy, 40 times that used by humanity in total, comes amid an increasing rise in sea levels and continuing acidification
TL;DR
- A record 23 zettajoules of heat were absorbed by the world's oceans in the past year.
- Sea levels have risen by an average of 3.8mm per year since 1999, with an accelerated rate between 2012 and 2025.
- The global ocean has become 17% more acidic over the last 40 years.
- Oceans have absorbed about one-third of human-emitted CO2 and 90% of trapped heat from greenhouse gases.
- Europe's seas, particularly the Mediterranean and Black Seas, experienced record marine heatwaves.
- 84% of the world's coral reefs experienced bleaching-level heat stress between January 2023 and September 2025.
- Nearly 5% of the ocean has seen a persistent shift in phytoplankton growth patterns over the past 30 years.
- Four emperor penguin colonies in Antarctica experienced total breeding failures in 2022 due to record-low sea ice.
- More than one-third of humanity was subjected to dangerous levels of ground-level ozone pollution due to extreme heat and air pollution.
- Air pollution, including wildfire smoke and ozone, can travel thousands of kilometers, underscoring the need for coordinated global action on climate change and air quality.