Record ocean warming in 2025

In 2025, global ocean warming continued unabated, surpassing every previous record since records began. According to a recent study, 33% of the ocean recorded temperatures that ranked among the three highest in history (1958-2025), while 57% recorded the five highest values. These areas include the South Atlantic Ocean, the Mediterranean Sea, the North Indian Ocean, and the Southern Ocean. In fact, although the average global sea surface temperature in 2025 decreased by 0.12 ± 0.03°C (due to La Nina conditions) compared to 2024, it was 0.49 °C higher than the 1981-2010 period.

As 2025 ranks as the second warmest year on record, it reflects the long-term accumulation of heat in the climate system, which is due to the increase in greenhouse gas concentrations, which also reached a historic high in 2025.

With the Earth now trapping much more energy than it can release into space, ocean warming is the strongest evidence that the planet’s energy balance has been disrupted. By absorbing 90% of the extra heat, the ocean affects the frequency and intensity of heat waves, alters atmospheric circulation, and accelerates sea level rise, evaporation, and atmospheric humidity, leading to more intense rainfall and stronger storms. sea level, evaporation, and atmospheric humidity, which leads to more intense rainfall and stronger tropical cyclones. At the same time, the warming of the climate system is leading to a reduction in ice cover in the Arctic and Antarctic, which reached historic lows in 2025, as well as to the occurrence of extreme weather events. These phenomena result from a combination of long-term warming and natural climate variability, which is amplified by a warmer atmosphere that holds more water vapor.