Average sea surface temperature outside the polar regions reached 21.1C on Saturday, the highest on record, the Copernicus Climate Change Service reported. More than 90% of the heat trapped by carbon dioxide from fossil fuel burning goes into the oceans, and C3S scientist Dr Samantha Burgess said the record is a clear signal of an ocean under growing stress. The spike is being intensified by a fast developing El Niño that C3S says is set to be the hottest in at least a century and has already contributed to low monsoon rain in India, major fires in Indonesia, and elevated fire concerns in Australia. Warmer oceans drive thermal expansion that raises sea levels, transfer more energy and water vapor to the atmosphere to intensify storms, and underpin marine heatwaves, which the agency says have more than tripled in global days since the early 1990s. A hotter ocean also absorbs less CO2, weakening a major natural buffer against warming, and Brian O'Donnell of Campaign for Nature urged rapid cuts to fossil fuel emissions alongside durable protection of kelp beds, mangroves, marshes, and reefs. The C3S dataset covers oceans outside the polar regions and extends back to 1979 when satellite records began delivering high-quality data, while the Arctic continues to be the fastest-heating region on Earth.
