Scientists examined a mass of EU-funded research on the impacts of climate change on Europe's marine environment and identified the gaps and priorities for future work.
"Change has been clearly visible and is much more rapid than we thought was possible," said Carlo Heip, chair of the CLAMER project and lead author of the report.
Over the past 25 years, sea-water temperatures have increased as Arctic sea ice has melted. The combination of rising sea levels and increased winds has contributed to the erosion of 15% of European coasts, the report said.
Warming has speeded up in the past 25 years at around 10 times faster than the average rate of increase in the 20th Century, it added.
From 1986 to 2006, sea surface temperature rises for European waters were three to six times higher than the global average.
"Scenario simulations suggest that by the end of the 21st Century, the temperature of the Baltic Sea may have increased by 2 to 4 degrees centigrade, the North Sea by 1.7 degrees, and the Bay of Biscay by 1.5 to 5 degrees," the report said.
Melting ice sheets and glaciers add more uncertainty. Current estimates for 2100 suggest European sea levels could rise 60 cms and up to 1.9 metres in some British coastal areas.
Sea-level rise threatens populations in all low-lying areas of Europe, but countries such as Britain, France and the Netherlands could be less vulnerable because they are rich enough to adopt coastal protection measures.
Changes in the marine food chain have also occurred as organisms have migrated to the Atlantic from the Pacific via seasonal ice-free passages through the Arctic.
Species that thrive in one ocean may disrupt other marine ecosystems, the report said.
Arctic sea ice this summer was also predicted to melt to its lowest – or second lowest – extent ever, according to both the University of Bremen and the US-based Snow and Ice Data Centre.
The five biggest Arctic melts in a 32-year satellite record have all happened in the last five years, probably because of a combination of climate change and natural weather patterns.
"An ice-free [Arctic] summer is rapidly on its way," said Kim Holmen, research director at the Norwegian Polar Institute.
EurActiv with Reuters