There's some speculation involved, and a little hyperbole. Basically, if the gulf stream shuts down, Northern Europe will basically become virtually uninhabita

There's some speculation involved, and a little hyperbole. Basically, if the gulf stream shuts down, Northern Europe will basically become virtually uninhabitable - not in the sense as in "nobody can live there", but more like "the population density supported will be more like Manitoba/Saskatchewan/Alberta or Mongolia/Kazakhstan". Scandinavia is the same latitude as Greenland and the UK/Germany/Poland is the same latitude as north/central Canada, after all. If the warming influence of the gulf stream disappears, expect the ports to freeze over (similar to the Hudson Bay) and the climate to become similar. It may be counteracted somewhat by general global warming - like the Northwest Passage may open up - but at best you should still expect climate more like Vladivostok or Juneau than present-day Europe. AMOC/gulfstream shutdown is not a given, there is still scientific debate about it. But the scientific evidence is starting to pile up, along with evidence that circulation patterns are weakening right now. If you Google [amoc shutdown] you can read a quick overview.