The Oceans Just Keep Getting Hotter

A recent study published in Advances in Atmospheric Science reveals that the world’s oceans absorbed a record-breaking 23 zettajoules of heat in 2025, surpassing the previous year’s 16 zettajoules. This research, conducted by over 50 scientists from the U.S., Europe, and China, highlights the unprecedented rate at which ocean heat content is increasing. To contextualize the immense energy absorbed, coauthor John Abraham compares it to the explosive energy of 12 Hiroshima atomic bombs detonating in the ocean, or the energy required to boil 2 billion Olympic-sized swimming pools. The oceans act as the planet’s largest heat sink, absorbing more than 90% of excess atmospheric warming, with heat penetrating not just the surface but also deeper ocean layers through circulation. While sea surface temperatures in 2025 were slightly lower than in 2024—partly due to the transition from a strong El Niño to a weak La Niña event—these surface measurements do not