The scientists at Woods Hole have some interesting info on their website. It is about the chance that global warming will likely unleash a mini Ice Age within the next 10 years. They (I wish these guys had a “mini Ice Age weblog” we could read in real time as they update things) predict the shift could happen extremely quickly once unleashed.
The mechanism for this is simple. The north pole's ice cap is melting quickly due to global warming. This has created an extremely large pool of fresh water near the ice cap. That pool of water will eventually drift southward. When it does, it will disrupt the gulf stream due a change in the density of the water. Without the gulf stream, the northeast US and Europe will quickly experience a 10 degree drop in temperatures.
This mini Ice Age would be similar to the one we experienced between 1300 and 1850. Remember that picture of Washington crossing the Delaware river? See the ice? That doesn't happen anymore. According to the Wood's Hole scientists, it will again. There is also an outside chance that disruption of the gulf stream could disrupt the entire ocean conveyor system which would impact the rest of the world. [John Robb's Radio Weblog]