Scientists say the chance that global warming will cause severe local cooling in Europe, and possibly North America, is far smaller than they had previously thought.

The previous prediction ran roughly as follows:

As the Green Land ice sheet melts more and more fresh water flows into the North Atlantic, near the point where the warm water brought up by the Gulf Stream cools and sinks (cold water is heavier than warm water).

That sinking water is, in effect, the engine driving the Gulf Stream. And since fresh water is lighter than salt water it was feared the melt water from Greenland might keep the cold Gulf Stream water from sinking. That, it was thought, would break down the Gulf Stream and in doing so remove a lot of warmth from the North Atlantic in general and Europe in particular.

But further research has now shown that the Greenland ice sheet would have to melt virtually all at once for the melt water to truly break the Gulf Stream’s engine.

Scientists still think it likely the Gulf Stream will be slowed, by about 25%, but don’t think it will break down entirely. In that scenario any cooling in Europe due to the weaker Gulf Stream would easily be offset by the warming of the atmosphere.

Read more on this story from The International Herald Tribune