ACC News Brief
Climate Science Extra-polar global ocean (60°S–60°N)
Observed record — C3S/ERA5 final daily values
Extra-polar ocean surface temperature hit a daily record on August 21–22
What happened
Copernicus’ ERA5 series put the daily mean sea-surface temperature across the extra-polar global ocean (60°S–60°N) at 21.104°C on both August 21 and 22, above the previous 21.091°C daily high reached on several days in March 2024. The Copernicus release highlights August 22 and places the record in the context of a strong developing El Niño superimposed on the ocean’s long-term human-driven warming. The ERA5 series used for this comparison begins in 1979.
ACC context
This is a measured daily surface indicator, not a measurement of every ocean basin or the ocean’s full-depth heat content. Short-term variability such as El Niño can affect the timing and magnitude of a daily record, while human-caused warming raises the long-term background. Those roles should be described together, not treated as competing explanations.
Why it matters
Exceptionally warm surface waters can intensify marine heat stress and affect weather, coastal conditions, fisheries, and ecosystems. The consequences vary by region, however, and a global extra-polar average cannot by itself establish a specific local ecological impact.
What to watch
- Whether extra-polar daily and monthly sea-surface temperatures remain near record levels as El Niño develops.
- Regional marine-heatwave extent, duration, and observed impacts rather than global averages alone.
- Full-ocean heat-content indicators, which track a different and broader part of the climate system than surface temperature.
Sources & evidence
- Copernicus: Daily global sea surface temperature breaks 2024 recordCopernicus Climate Change Service official release, published August 24, 2026. It confirms the August 22 record, the 60°S–60°N scope, the ERA5 series beginning in 1979, and the El Niño plus long-term human-driven warming context.
- ERA5 daily sea-surface-temperature series for 60°S–60°N oceanC3S/ECMWF data file, last updated August 24, 2026 and checked August 26. Final rows report 21.104°C on August 21 and 22; the prior 2024 high was 21.091°C.
- Copernicus Climate PulseC3S near-real-time climate-variable interface and methodology context, accessed August 26, 2026.
- Earth is simmering in its hottest water temps on record, and that’s bad for fish and usAssociated Press reporting published August 24, 2026 at 19:18:51 UTC. It supplies independent expert context; the official C3S release and data series remain the evidence for the record.
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