In 2025, Earth’s oceans absorbed more heat than in any year since modern measurements began—an estimated 23 zettajoules, equivalent to roughly 37 years of humanity’s current energy use, largely stored beneath the surface where most of us will never see it.

In 2025, Earth’s oceans absorbed more heat than in any year since modern measurements began—an estimated 23 zettajoules, equivalent to roughly 37 years of humanity’s current energy use, largely stored beneath the surface where most of us will never see it.

Earth’s oceans ended 2025 with more heat stored in their upper 2,000 meters than in any other year since modern measurements began, after an estimated increase of 23 zettajoules. The increase was recorded even though the average sea-surface temperature eased from the extraordinary high of 2024. The finding comes from an international annual synthesis led by Yuying Pan of the Chinese Academy of Sciences and published in Advances in Atmospheric Sc…