Richard Seager in American Scientist:
If you grow up in England, as I did, a few items of unquestioned wisdom are passed down to you from the preceding generation. Along with stories of a plucky island race with a glorious past and the benefits of drinking unbelievable quantities of milky tea, you will be told that England is blessed with its pleasant climate courtesy of the Gulf Stream, that huge current of warm water that flows northeast across the Atlantic from its source in the Gulf of Mexico. That the Gulf Stream is responsible for Europe’s mild winters is widely known and accepted, but, as I will show, it is nothing more than the earth-science equivalent of an urban legend.
This is not to say that there is no climatological mystery to be explained. The countries of northern Europe do indeed have curiously mild climates, a phenomenon I didn’t really appreciate until I moved from Liverpool to New York. I arrived in the Big Apple just before a late-summer heat wave, at a time when the temperature soared to around 35 degrees Celsius. I had never endured such blistering temperatures. And just a few months later I was awestruck by the sensation of my nostrils freezing when I went outside. Nothing like that happens in England, where the average January is 15 to 20 degrees warmer than what prevails at the same latitude in eastern North America. So what keeps my former home so balmy in the winter? And why do so many people credit the Gulf Stream?
Like many other myths, this one rests on a strand of truth.