Oceans reached highest recorded heat levels in 2025, study finds

Time reported that a study published in the peer-reviewed journal Advances in Atmospheric Sciences found the Earth’s oceans were hotter in 2025 than in any year since modern measurements began.

The analysis found the upper 2,000 meters of the ocean absorbed a record-setting 23 zettajoules more energy than in 2024—equivalent to roughly 37 times the energy the world consumed in 2023. The study measured ocean heat content, which tracks excess heat stored in the oceans; oceans have absorbed about 90% of the excess heat from planetary warming over the past century. Global average sea-surface temperatures in 2025 were the third highest on record and about 0.5°C (1°F) above the 1981–2010 baseline, with the South Atlantic, North Pacific and the Southern Ocean among the warmest areas.

The report links warmer oceans to rising sea levels (partly from thermal expansion) and more extreme weather, noting increased hurricane intensity and slower storm speeds that can prolong damage; “last year was only the second year in recorded history in which at least three Category 5 hurricanes formed in the Atlantic basin,” the study said. A 2025 report cited in the coverage found 80% of warm-water coral reefs are experiencing unprecedented heat waves, bleaching and die back. The study’s authors note that, without global efforts to reduce emissions, temperatures will only continue to rise.

Key Topics

Science, Ocean Heat Content, Sea-surface Temperature, South Atlantic, North Pacific, Southern Ocean