Ah, the old gulf stream effect! I remember a very good edition of Horizon on the potential effects of global warming on the gulf stream, and therefore the potential cooling effects on Britain. (I love Horizon, and hate Panorama - completely irrelevant, but I thought I'd throw it in...)
That was a number of years ago now (must have been when I was in year nine, or sometime around then). Only a few weeks later we started studying global warming in Chemistry and we had to write an essay on the potential effects of global warming on Britain - the Chemistry teacher was impressed that I'd gone for this unusual, more scientific view. Of course it did help that I had very recently watched that Horizon!