The long term future of the Gulf Stream is now under threat; the Arctic ice is melting and the fear among oceanographers is that the cold water will not sink in the Norwegian Sea, thus switching off this transatlantic heat conveyer. Northern Europe would then freeze, and this apparent paradox - that global warming could bring about a new european ice age - seems to have caught the popular imagination. Orsenna explores the Gulf Stream, its past and its future, both in celebration and in lament of its possible demise.