Since measurements began in 1969, the North Sea has never been as warm as it was last year, announced the German Federal Maritime and Hydrographic Agency (BSH) on Wednesday.
The agency sees global warming as an explanation for the data.
"In 2025, the North Sea reached an average temperature of 11.6°C, the highest value recorded in the data series since 1969," the BSH said in a statement.
For the Baltic Sea, 2025 was also almost a record year. According to BSH measurements, the average annual temperature there last year was 9.7°C, or 1.1 degrees higher than the average for the period 1997 to 2021.
"This makes 2025 the second warmest year for the Baltic Sea since the BSH data series began in 1990," the agency said. Only 2020 was warmer.
BSH President Helge Heegewaldt used the publication of the data to once again warn of the consequences of climate change. "Even if we were to stop global greenhouse gas emissions immediately, sea levels would probably continue to rise for centuries."
Therefore, it is important to "do more to protect the climate," he argued.
The warming of the North Sea and the Baltic Sea is part of the broader context of warming seas around the world as a result of climate change.
According to the UN climate panel IPCC, the rate at which the oceans are warming has more than doubled since 1993.
