Will Europe get the big chill?
It's not out of the question that global warming could produce cooling rather than warming across northwest Europe. This strange scenario was first proposed decades ago by geochemist Wallace Broecker, and it was the idea behind the blockbuster 2004 film The Day After Tomorrow, where it played out on a cinema-convenient time scale of a few days (in real life, the process would take at least a few years and perhaps many decades). The idea goes like this: warmer temperatures across northeastern Canada, Greenland and the Arctic result in heavier precipitation and/or more melting of ice and snow. The run-off feeds into the North Atlantic and encounters a conveyor belt of warm tropical water flowing north across the Atlantic. Normally, this warm water flows north with the Gulf Stream and its northern extensions, then cools, descends and flows back south more than 3000nV 10,000ft beneath the surface. But if enough rain or meltwater were to enter the North Atlantic, it could pinch off the Gulf Stream and either slow or shut down the conveyor belt. The result would be much colder waters to the west of England and the Continent Studies of prehistoric climate show that runoff from glacial melt did apparently trigger two major regional coolings between about 12,000 and 8,000 years ago. Computer models have disagreed on whether this process might happen again in the foreseeable future. More recently, the consensus from an extensive set of ocean-atmosphere simulations released in 2005 shows the conveyor slowing by around 30 percent or so over the next century.That wouldn't be enough to encase the British Isles in ice, but should it materialize it might keep the region from warming as quickly as other parts of the world.