Overview
- Copernicus confirmed the global daily average sea-surface temperature reached 21.1 °C on 22 August 2026, beating the previous daily record from March 2024.
- Scientists say the spike is driven by a strong El Niño that is adding to a long-term, human-driven rise in ocean temperatures rather than replacing that trend.
- Copernicus had already recorded the highest monthly global SST in July 2026 at 20.96 °C, showing the year’s warming is persistent across multiple time scales.
- Rising sea-surface temperatures have more than tripled global marine heatwave days since the early 1990s and increase risks to coral reefs, fisheries, coastal communities and extreme rainfall and storm intensity.
- Longer-term monitoring since 1979 shows a steady upward trend in ocean warmth that weakens the ocean’s carbon uptake and raises the chance of further climate and ecosystem feedbacks.