The number that best describes the state of the planet right now is not an air temperature but 20.96 degrees Celsius (69.7 degrees Fahrenheit), the average surface temperature of the world’s extra-polar oceans in July, as computed by the Copernicus Climate Change Service from its ERA5 reanalysis. It is the warmest July in the satellite record, and it matters in a way that headline air-temperature records often do not: the ocean is where the excess heat of a warming planet goes.
The record is narrow but unmistakable. July 2026 edged past the previous July high of 20.89°C set in 2023, a margin of 0.07°C. The independent Copernicus Marine Service, using a different, higher-resolution analysis system called GLO12, computes a July average of 21.00°C with an uncertainty of about 0.11°C, statistically indistinguishable from the same conclusion. June 2026 was also the warmest June on record, so the global ocean has now logged two consecutive record-setting months, following an April and May that finished a close second to 2024.
The contrast with the air
The ocean’s climb stands out because the atmosphere’s record streak has stalled. July 2026 was only joint-second warmest for global surface air temperature, tied with 2024 and behind July 2023. Air temperatures respond quickly to year-to-year fluctuations such as El Niño. The ocean, with its enormous heat capacity, integrates the warming signal more slowly and more steadily. When the air record stalls while the sea record advances, the discrepancy is itself information: the heat is still accumulating, but the atmosphere is no longer where it shows up first.
The ocean absorbs the overwhelming majority of the extra energy trapped by greenhouse gases. Because water expands as it warms, thermal expansion alone accounts for roughly a third of sea-level rise so far, before land ice melt is even counted. The same stored heat turns ordinary weather into extreme weather: hotter seas feed more energy and moisture into tropical storms, intensifying them and loading them with heavier rainfall.
Marine heatwaves at record extent
The July average hides the sharper story of regional extremes. Copernicus Marine reported that intense or stronger marine heatwaves covered 27 percent of the global ocean for at least one day during the month, the widest extent in 34 years of records, up from 22 percent in 2024. On July 31, conditions qualifying as marine heatwaves spanned 37 percent of the ocean. The Mediterranean was hit hardest: 79 percent of the basin experienced intense marine heatwaves, and the sea’s average surface temperature reached a record 27.07°C, surpassing July 2025’s 26.68°C.
Sustained ocean heat drives mass coral bleaching, kills kelp forests, disrupts fisheries and pushes species toward cooler waters. The Atlantic coast and the western Mediterranean saw the strongest and most severe heatwave conditions, according to the Copernicus analysis.
Why now
Two forces are combining. The long-term warming from greenhouse-gas emissions sets the baseline, and a developing El Niño adds a push on top. The World Meteorological Organization announced El Niño conditions on June 2, and NOAA confirmed them on June 11, forecasting that the event would strengthen through the second half of the year. El Niño shifts vast amounts of heat within the ocean and releases some of it to the atmosphere, which is part of why the coming months bear watching.
Samantha Burgess, strategic lead for climate at the European Centre for Medium-Range Weather Forecasts, which implements Copernicus, described the July figures as consistent with the continuing warming of the climate system. Simon Van Gennip, lead oceanographer at the Copernicus Marine Service, noted that the record ocean warmth is expanding the area affected by marine heatwaves at an unprecedented rate.
What the number does not say
A few caveats keep the record in perspective. The 20.96°C figure is an absolute average over the extra-polar ocean between 60 degrees south and 60 degrees north, not an anomaly. Copernicus does not publish a single official monthly anomaly for sea-surface temperature the way it does for air, which makes month-to-month comparisons less intuitive. Two consecutive record months are a signal, not a trend; a single La Niña year could pause the sequence even if the underlying warming continues. And monthly records remain sensitive to methodology, which is why the two Copernicus systems land at 20.96 and 21.00°C rather than one identical number.
The larger point survives the caveats. The ocean is the planet’s most reliable thermometer, and it is still climbing. July’s record is one more line in a ledger that has been filling steadily for decades. Unlike the air-temperature streak, the sea’s version has not yet shown signs of stopping.
Sources:
- BBC News, “World’s oceans hit record-high July temperatures” (Aug 10, 2026): https://www.bbc.co.uk/news/articles/cpvw8vmmgrwo
- Copernicus Climate Change Service press release (Aug 10, 2026): https://climate.copernicus.eu/copernicus-highest-july-global-ocean-surface-temperatures-exceptionally-hot-dry-conditions-fuel
- Copernicus Marine Service / Mercator Ocean, July 2026 ocean temperature bulletin: https://www.mercator-ocean.eu/bulletin/ocean-temperature-bulletin-july-2026/
- The Guardian, “Global seas hottest temperature July” (Aug 10, 2026): https://www.theguardian.com/environment/2026/aug/10/global-seas-hottest-temperature-july-scientists
- NOAA NCEI, June 2026 global climate report: https://www.ncei.noaa.gov/news/global-climate-202606