Global sea surface temperatures reached a record daily high of 21.1°C on August 22, according to data from the European Union’s Copernicus Climate Change Service, surpassing previous benchmarks as a developing El Niño adds heat to an ocean already warming from long-term climate change. The reading edges past the previous daily high of 21.09°C set in March 2024 and outpaces the previous August record of 20.98°C set in 2023, signaling a persistent upward trend in marine temperatures during a month when waters typically begin to cool.
Drivers Behind Record Ocean Temperatures
The warmth is driven by a combination of long-term greenhouse gas emissions and the emergence of a strong El Niño in the tropical Pacific. Oceans absorb more than 90% of the excess heat trapped by human activities, primarily the burning of fossil fuels. Samantha Burgess, strategic lead for climate at the European Centre for Medium-Range Weather Forecasts, noted that El Niño is adding heat to the system on top of decades of human-driven warming. The World Meteorological Organization forecasts that the El Niño event will continue to strengthen in the coming months, potentially reaching levels not seen for several decades.
Regional Marine Heatwaves in Europe and the UK
The heating is not restricted to the tropical Pacific. Waters far from El Niño’s usual zones are experiencing extreme conditions, including the seas surrounding the UK and Europe. According to Prof. Tim Smyth, director of science at Plymouth Marine Laboratory, the western English Channel has endured almost continuous marine heatwave conditions for more than three years, peaking at 7°C above normal in July. Thomas Frolicher, an environmental physicist at the University of Bern, stated in a study published last week that Europe’s seas—stretching from Atlantic waters off Ireland to the Mediterranean—are experiencing an alarming temperature surge driven by climate change and fossil fuel combustion.
Ecological and Environmental Consequences
Rising ocean temperatures threaten severe impacts on marine ecosystems and coastal communities. According to Copernicus data, the global ocean has experienced a sharp increase in marine heatwaves, with the number of heatwave days more than tripling since the early 1990s. These intense thermal events can damage coral reefs, harm seagrass meadows, and disrupt marine food webs, forcing fisheries and aquaculture industries to adapt as species shift locations. Additionally, warmer water expands, raising sea levels and increasing coastal flood risks. Warmer seas also transfer additional moisture and energy into the atmosphere, which can intensify storms and reduce the cooling effect of sea breezes on coastal land areas. Furthermore, Copernicus notes that warmer water is less efficient at absorbing carbon dioxide, potentially weakening one of the planet’s primary carbon sinks.
