Ocean heat record levels were registered in June, as the world’s seas reached their highest surface temperature for the month since measurements began, according to the European Union’s Copernicus climate monitoring services.
The global average sea surface temperature for June reached 20.98°C, surpassing the previous June records set in 2023 and 2024. Copernicus data also show that the average sea temperature for the first half of the year stood at 20.04°C, only slightly below the record registered for the same period in 2024.
The figures add to growing concern among climate scientists, as the oceans absorb most of the excess heat trapped by greenhouse gases. Warmer seas can influence weather systems, intensify marine heatwaves, affect fisheries and ecosystems, and contribute to sea-level rise.
Ocean heat record confirmed by EU monitoring services
The Copernicus Climate Change Service (C3S) and the Copernicus Marine Service both reported that global sea surface temperatures outside the polar regions have exceeded the record levels observed at the same time of year in 2023 and 2024.
According to Copernicus, C3S daily sea surface temperature data passed the 2024 level on 21 June, reaching 20.86°C. Copernicus Marine data independently pointed to a record of 21.0°C on the same day, around 0.1°C above previous highs.
The records refer to the extra-polar ocean, between 60°N and 60°S, the area commonly used for global sea surface temperature monitoring. This excludes polar waters, where sea ice and seasonal variability require separate analysis.
Copernicus said the simultaneous confirmation by two independent systems strengthens the reliability of the finding. C3S uses the ERA5 reanalysis produced by the European Centre for Medium-Range Weather Forecasts (ECMWF), while Copernicus Marine relies on ocean analysis and forecast systems developed by Mercator Ocean International.
El Niño could push temperatures higher
The new record comes as El Niño conditions are developing in the equatorial Pacific. El Niño is a natural climate phenomenon linked to unusually warm surface waters in the central and eastern Pacific, with effects on weather patterns across the world.
Copernicus said the current ocean warmth was expected in the context of the developing El Niño, but also reflects the broader trend of human-driven climate change. Over the past three years, the global extra-polar ocean has been between 0.35°C and 0.73°C warmer than the long-term average.
Carlo Buontempo, Director of the Copernicus Climate Change Service at ECMWF, warned that current conditions may point to a further rise in global temperatures. He said that “we are likely to see more temperature records fall in the coming months.”
The World Meteorological Organization had already indicated in June that there was a high probability of El Niño conditions developing during the northern summer. ECMWF forecasts also suggest that the event could become unusually strong later in the year.
Why warmer oceans matter for Europe
Higher ocean temperatures do not remain confined to the sea. They can keep the atmosphere warmer for longer, increase evaporation and provide more energy to storms. This can raise the risk of heavy rainfall, flooding and more intense weather extremes.
The effects are also visible around Europe. At the end of June, Copernicus Marine data showed sea surface temperature anomalies of up to 6°C in parts of the western Mediterranean, especially near southern France and along the western coast of Italy. Anomalies also increased in the southern North Sea and the Baltic Sea.
For Nordic and Baltic countries, warmer seas are particularly relevant because they can affect marine ecosystems, fish stocks and coastal weather patterns. The Baltic Sea is already a sensitive marine environment, with pressure from warming, pollution and low oxygen levels. Further marine heatwaves could add stress to ecosystems that are important for coastal communities and regional economies.
A signal from a changing climate system
Scientists caution that a single monthly or daily record does not define the climate trend on its own. However, the persistence of very high sea surface temperatures since 2023 has made the oceans one of the clearest indicators of the planet’s energy imbalance.
Copernicus said it is still monitoring whether the June exceedance is temporary or the beginning of a more persistent phase. The coming months will be important because global sea surface temperatures usually remain high during the northern summer, while El Niño can transfer additional heat from the ocean to the atmosphere.
The latest ocean heat record therefore matters beyond climate statistics. It points to a system in which warmer seas are increasingly shaping weather, ecosystems and policy choices in Europe and across the world.
