Oceans hit highest temperature on record

New data indicates that the world's oceans have reached their highest temperature ever recorded. The average surface temperature of the planet's seas, outside the polar regions, reached 21.1C (70F), surpassing the previous record of 21.09C set in March 2024. This alarming spike in ocean temperatures, attributed to human-caused climate change and the growing El Niño weather phenomenon, has significant implications for extreme weather, sea levels, and marine life.

Dr Samantha Burgess, deputy director of the Copernicus climate change service, emphasized that this record underscores the growing stress on our oceans. While El Niño is adding heat to the system, it is exacerbating the effects of decades of human-driven warming. Notably, average worldwide sea temperatures typically peak in March or April, yet this year's record-breaking temperatures have already been observed in August.

The southern hemisphere's larger share of the ocean surface influences these global averages, making the timing of this record particularly concerning. Dr Jeremy Grist, a senior research fellow at the National Oceanography Centre in Southampton, warned that the current El Niño could become the strongest in centuries, potentially pushing ocean temperatures even higher.

The record-breaking heat is evident not only in regions influenced by El Niño but also in areas far from its Pacific impact, such as the UK and Europe, where prolonged marine heatwave conditions have persisted for over three years. Warmer seas, a direct consequence of human-induced climate change, exacerbate extreme weather, intensify heatwaves on land, and raise sea levels, threatening coastal communities.

The warming oceans also pose a severe threat to marine ecosystems, including coral reefs, which are already under increasing pressure from marine heatwaves.