The great currents on the ocean surface are complemented by currents at the bottom of the ocean to make up a complex conveyor belt. As water moves from the equatorial regions it is warmed. As it is warmed, it evaporates and becomes saltier. The current known as the Gulf Stream moves across the Atlantic to give Great Britain and northern Europe the relatively pleasant climate it enjoys. As the current move north, it cools and because it is saltier than the surrounding water, it is heavier. The current dives down to the bottom, pulls a Uey and heads south again.

One of the effects of global warming has been a reduction in glacier thickness. "A NASA study of Greenland's ice sheet reveals that it is rapidly thinning. In an article published in the July 21 issue of Science, Bill Krabill, project scientist at the NASA Goddard Space Flight Center's Wallops Flight Facility, Wallops Island, VA, reports that the frozen area around Greenland is thinning, in some places, at a rate of more than three feet per year." If it is 3 feet a year now, what will be the rate in 10 or 20 years? Scientists are worried that the increase in fresh water will stop the conveyor belt. It is certainly a concern for Queen Elizabeth and Tony Blair.

Here is a very well done explanation  Press

Here is a recent article about the conveyor belt and its effects on sea life.  Press

Here's why the Queen of England is concerned about global warming   Press

Anthony Wood of the Philadelphia Inquirer offers us this article.  Press

Alan Alda just hosted a program on Scientific American Frontiers on your PBS station called Hot Planet - Cold Comfort