Ocean at 21.1°C: Why August’s Record Heat Threatens Global Shipping
The Copernicus Climate Change Service confirms the highest daily global sea surface temperature on record.
Global sea surface temperatures have reached an unprecedented high, with the Copernicus Climate Change Service (C3S) reporting a daily average of 21.1°C on 22 August 2026. This surpasses the previous record of 21.09°C, set in March 2024, and marks a significant departure from historical patterns.
The new record is particularly striking because it occurred in August, a month when ocean temperatures typically do not peak. Normally, the highest sea surface temperatures are observed in March or April, following the southern hemisphere’s summer. The previous highest August temperature, recorded in 2023, was 20.98°C. The C3S ERA5 dataset, which provides data back to 1979, confirms this trend of rising temperatures, with 2026 seeing multiple monthly records and near-records in extra-polar ocean regions (60°S to 60°N).
A combination of long-term climate change and a developing El Niño event in the tropical Pacific is driving this increase. The World Meteorological Organization (WMO) expects El Niño to strengthen in the coming months, potentially reaching intensities not seen in decades.
Samantha Burgess, Strategic Lead for Climate at the European Centre for Medium-Range Weather Forecasts (ECMWF), warned that this record reflects an ocean under growing stress. She noted that while El Niño is adding heat, it is doing so on top of decades of human-induced warming. The consequences are already evident, with the number of marine heatwave days more than tripling since the early 1990s.
An Unusual Timing for Record Temperatures: Ocean
The impacts of warmer oceans extend beyond marine ecosystems. Higher sea surface temperatures contribute to sea-level rise through thermal expansion, increasing risks for coastal communities and low-lying island nations. Marine heatwaves, which are becoming more frequent and intense, threaten critical ecosystems like coral reefs and seagrass meadows. These ecosystems support marine food webs and industries such as fisheries and aquaculture, which are vital for global food security.
Additionally, a warmer ocean has broader climatic effects. It transfers more heat and moisture to the atmosphere, potentially intensifying rainfall and storm systems. Warmer waters also absorb less carbon dioxide, weakening one of the planet’s key natural buffers against climate change. Scientists at C3S continue to monitor these developments to determine whether the recent temperature spike is temporary or part of a longer-term trend.
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