Could Europe Freeze?

Earlier this week I received a viewer question from Paul Sanderson:
I have heard it said that if the North Atlantic Conveyor stops or breaks down then England will see temperatures dip in a very short space of time to temperatures below -100° F.  Is that true?  And if so how does that happen?  I know England is on the same line of latitude as Alaska and that state gets very cold in winter, far colder than England.

I'm sure many of you have watched "The Day After Tomorrow" and I'll admit I was probably one of the first to go out an buy the DVD when it came out.  Is something like that possible?  Can half of North America freeze over within a matter of days if the Ocean Conveyor Belt were to shut down?  Well, current theories on the cause of abrupt climate change focus on the sudden shut down and start up of the Thermohaline Circulation (the ocean conveyor belt).  It is a network of ocean currents that move around the globe.  Warm, salt water is transported northward through the Atlantic and up the East Coast of the US to form the Gulf Stream and then heads to the higher latitudes near Europe and Greenland.  Because of the transport of the warm air - heat is released into the atmosphere keeping Europe and much of North America warmer, particularly in the winter.  The warm air then cools and because cold water is more dense than warm water it sinks and travels back south towards Antartica.  This circulation can be found all across the globe. 

I know many people have come to their own conclusions about global warming and maybe we can get a blog post going about that.  But, scientists are worried that the freshwater melt from glaciers will throw off the balance of this circulation by adding more freshwater into the oceans.  If this were to happen, then the warmer water would not be allowed to transport north, therefore, altering the climate within a matter of years.

Now I'm not sure if the temperature in Europe would fall to minus 100° F but it would have a major impact on it's climate.  Some studies have shown that the annual average temperature would drop up to 6° F in Europe and 5° F in North America.  This could mean that winters would last into summer and winter storms could even be stronger.  There have also been links to abrupt climate change in the past, looking back at ice core samples, to the shut down or slow down of the ocean conveyor belt.

So, what are your thoughts on this?  We would like to know!