Warming of the North and Baltic seas continues, German figures show

The warming of both the North and Baltic seas in continuing, with the North Sea posting a 56-year record, according to figures released by Germany's Federal Maritime and Hydrographic Agency (BSH) on Wednesday.

The North Sea's recorded average surface water temperature was 11.6 degrees Celsius in 2025 - the highest value in the BSH data series since 1969.

Compared to the long-term average from 1997 to 2021, the North Sea was 0.9 degrees warmer, according to the BSH. 

Every month in the North Sea last year was well above the long-term average, with June and December even setting records, according to Tim Kruschke, head of the BSH's Marine Climate Issues Department.

The annual average surface temperature in all areas of the North Sea in 2025 was at least 0.5 degrees above the long-term average, and in many regions even more than 1.0 degrees above. 

Baltic Sea posts second warmest year

Scientists calculated an average surface temperature of 9.7 degrees for the Baltic Sea last year. This is an increase of 1.1 degrees compared to the long-term average from 1997 to 2021.

This makes 2025 the second warmest year for the Baltic Sea since the BSH began recording data in 1990. Only in 2020 was it warmer.

The BSH examines the surface temperatures of both seas on a weekly basis, combining satellite data with measurements from stations and ships.

Climate projections by the Intergovernmental Panel on Climate Change (IPCC) suggest global sea levels could rise by 0.63 to 1.01 metres by 2100 if greenhouse gas emissions do not fall dramatically.