Last year, the oceans absorbed a record-breaking amount of heat — equivalent to 12 Hiroshima bombs exploding every second
The ocean absorbed more heat last year than in any year since modern measurements began around 1960, according to a new analysis published in Advances in atmospheric science.
The planet’s oceans absorb more than 90% of the excess heat trapped in Earth’s atmosphere by greenhouse gas emissions. As heat in the atmosphere builds up, heat stored in the ocean also increases, making ocean heat a reliable indicator of long-term pollution. climate change.
Scientists measure ocean heat in different ways. A common measurement is the global average annual sea surface temperature, the average temperature in the uppermost meters of ocean waters. The global sea surface temperature in 2025 was the third warmest on record, about 0.5°C (0.9°F) above the 1981 to 2010 average.
Another metric is ocean heat content, which measures the total thermal energy stored in the world’s oceans. It is measured in zettajoules: one zettajoule is equivalent to 1,000,000,000,000,000,000,000 joules. To measure heat content in 2025, the study authors evaluated ocean observation data from the upper 2,000 meters of the ocean, where most heat is absorbed, from NOAA’s National Environmental Information Centers, the European Union’s Copernicus Climate Change Service and the Chinese Academy of Sciences.
They found that in total, the ocean absorbed an additional 23 zettajoules of thermal energy in 2025, breaking the ocean heat content record for the ninth consecutive year and marking the longest streak of consecutive ocean heat content records on record.
“Last year was a crazy year, with crazy warming,” John Abrahammechanical engineer at the University of St. Thomas and co-author of the new study, said Wired.
Twenty-three zettajoules in one year is equivalent to the energy of 12 Hiroshima bombs explode in the ocean every second. This is also a significant increase from the 16 zettajoules of heat absorbed by the ocean in 2024. The warmest ocean areas observed in 2025 were the tropics and the South Atlantic, the Mediterranean Sea, the northern Indian Ocean, and the Southern Ocean.
The results provide “direct evidence that the climate system is out of thermal equilibrium and accumulating heat,” the authors write.
A warmer ocean promotes increased global precipitation and fuels more extreme tropical storms. Over the past year, higher global temperatures have likely been partly responsible for the harmful effects of Hurricane Melissa in Jamaica and Cuba, heavy monsoon rains in Pakistan, severe flooding in the central Mississippi Valleyand more.
“Ocean warming continues to have profound impacts on the Earth system,” the authors write.
This article was originally published on Eos.org. Read the original article.
