Between June 2 and September 10, the global ocean outside the polar regions experienced an unprecedented stretch of record-breaking warmth. Data shows sea surface temperatures remained higher than any previous year on record for 100 consecutive days, driven by ongoing climate change and the current El Niño event.
- 100 days of record ocean heat recorded since June
- Ocean absorbed 43% more heat in 2025 than 2024
- Rising sea temperatures worsen heatwaves and affect marine life
What happened
Scientists tracked sea surface temperatures from June 2 through September 10, revealing a historic stretch of 100 days during which global ocean temperatures outside polar areas set new records every day. Some of the highest readings were observed in late August, with temperatures exceeding 21 degrees Celsius (around 70 degrees Fahrenheit). This persistent heat surge is unusual in scale and duration, marking a new chapter in ocean warming.
This trend coincides with an intensifying El Niño event, which normally raises ocean temperatures, but climate experts emphasize that the underlying driver is human-induced climate change. The oceans have absorbed over 23 zettajoules of heat in 2025 alone — an energy amount equivalent to the continuous detonation of multiple atomic bombs each second throughout the year — causing warming not just at the surface but also in deeper ocean layers.
Why it feels good to know
Understanding these temperature records brings clarity to the scale of climate change’s impact on our planet, showing how much heat the oceans are accumulating due to greenhouse gas emissions. This knowledge encourages stronger global commitment to reducing fossil fuel emissions and protecting ocean health.
Additionally, tracking the interaction between El Niño and ongoing climate warming helps scientists anticipate and prepare for related weather impacts, such as heatwaves and changes in marine biodiversity. This proactive insight can guide policies and community actions to mitigate harm and sustain livelihoods dependent on the ocean.
What to enjoy or watch next
Keep an eye on ongoing developments related to the El Niño phenomenon and ocean temperature trends as the year progresses. These will influence weather extremes, including storms and heatwaves, especially in coastal regions where people and ecosystems are more vulnerable.
Meanwhile, the focus on sustaining marine ecosystems remains crucial. Initiatives to protect coral reefs, fisheries, and coastal habitats that are threatened by warming waters are essential to maintaining food security and biodiversity. Watching advancements in climate science and policy responses will be key to spotting hopeful solutions.