The Woods Hole Oceanographic Institute has a wonderfully clear summary (complete with animation) about how an abrupt cooling would take place in the North Atlantic as global warming dumps fresh water from Greenland into its adjacent waters. As the summary points out, rapid cooling in one area would be consistent with gradual overall warming of the planet.
Some global warming skeptics point to just such scenarios to say that climate science is confused and therefore unreliable. On the contrary, it is the increasing precision of measurements, observations and theory which enables climate researchers to imagine and quantify the probability of such scenarios.
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