Global ocean surface temperature hits record 21.1C in August, Copernicus says

September 8, 2026 at 08:00 PM2 min

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The global average sea surface temperature reached 21.1 degrees Celsius on Friday and Saturday, the highest on record, according to the EU's Copernicus climate service. The record, set in August when ocean temperatures normally near their annual low, surpassed the previous high from March 2024. Researchers warn the oceans are likely to keep warming as El Niño strengthens toward its expected peak between November and January.

Key Facts

The global average sea surface temperature reached 21.1°C on Friday and Saturday, narrowly above the previous daily record set in March 2024.
Copernicus strategic climate lead Samantha Burgess said the oceans are likely to keep warming, with El Niño expected to reach full strength between November and January.
Long-term warming from burning coal, oil and gas has raised ocean temperatures by 0.8°C, according to Burgess.
University of Seville researchers María C. Villarín and Alberto Celis found that warming in the Mediterranean is reaching deeper layers, not just the surface.

Record August Temperature

The EU's Copernicus climate service announced that the global average sea surface temperature reached 21.1°C on Friday and Saturday. The figure narrowly exceeded the previous daily record set in March 2024. Global sea surface temperature normally peaks in March or April and eases off by August, making the new record unusual for the time of year. Samantha Burgess, strategic climate lead at Copernicus, told AP that the oceans are likely to keep warming because the seasonal peak is still months away.

El Niño and Long-Term Warming

Burgess said warming driven by the burning of coal, oil and gas has raised ocean temperatures by 0.8°C over the long term. A still-strengthening El Niño is adding warmth on top of that long-term trend. Burgess and other forecasters expect El Niño to reach full strength sometime between November and January. Copernicus builds its estimates from satellite observations, buoy and ship data, and model reanalysis, publishing the global daily figure continuously.

Mediterranean Deep Warming

University of Seville researchers María C. Villarín and Alberto Celis examined historical temperature records from four Mediterranean coastal regions. Their results show surface waters are warming and the heat is now reaching deeper layers. Warmer seas transfer more heat and moisture to the atmosphere, which can intensify rainfall when meteorological conditions align. The researchers noted that heat stored below the surface must also be considered in this process.