Researchers from the UK's National Oceanography Centre say currents derived from the Gulf Stream are weakening, bringing less heat north.
Their conclusions, reported in the scientific journal Nature, are based on 50 years of Atlantic observations.
They say that European political leaders need to plan for a future which may be cooler rather than warmer.
The findings come from a British research project called Rapid, which aims to gather evidence relating to potentially fast climatic change in Europe.
more: BBC News