Long predicted as a possible effect of global warming, the slowing of the Gulf Stream which warms northern Europe has begun. The mechanism that warms Great Britain and Scandanavia--which are at the same latitude as Hudson Bay--is fairly straightforward: Cold water in the northern Atlantic sinks and draws in warm water from the tropics to replace it. Now, that mechanism is failing, and the cause is the melting of ice sheets off Greenland which are necessary to keep it going.
Not long ago the Pentagon studied the possible effects of the Gulf Stream coming to a stop. Although that hasn't happened yet, the first signs are in place, and the prospects for reversing the global warming trend that could lead to it over the next several decades are virtually nil.
(Via Flying Talking Donkey.)
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