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View Diary: The Antarctic Half of the Global Thermohaline Circulation is Collapsing (215 comments)

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  •  Has This Happened Before? (0+ / 0-)

    In the early 1700s? The mid 1100s? The first century BC?

    •  This level of polar freshening of surface water (1+ / 0-)
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      Calamity Jean

      Is unprecedented in human history. Since it is highly dependent on the rate of warming, I infer that it's unprecedented in the history of the planet.

      The world has warmed at other times, by rather more than 2 degrees C. It just took tens of thousands of years to do it. The analogy is that yes, I have frequently slowed from seventy miles an hour to zero, sometimes in less than five seconds. If I were to do it in less than .5 seconds, I would be dead. If I were to do it in a hundredth of a second, that would be comparable to what we have seen over the last century - and we're just getting started.

      I keep looking around for air bags.

      •  No - the Scientific Consensus Shows Rapid Change (0+ / 0-)
        Until a few decades ago it was generally thought that all large-scale global and regional climate changes occurred gradually over a timescale of many centuries or millennia, scarcely perceptible during a human lifetime. The tendency of climate to change relatively suddenly has been one of the most suprising outcomes of the study of earth history, specifically the last 150,000 years (e.g., Taylor et al., 1993). Some and possibly most large climate changes (involving, for example, a regional change in mean annual temperature of several degrees celsius) occurred at most on a timescale of a few centuries, sometimes decades, and perhaps even just a few years.
        The SAR reviewed the evidence of such changes since the peak of the last inter-glacial period about 120 ky BP (thousands of years Before Present). It concluded that: (1) large and rapid climatic changes occurred during the last Ice Age and during the transition towards the present Holocene; (2) temperatures were far less variable during this latter period; and (3) suggestions that rapid changes may have also occurred during the last inter-glacial required confirmation.

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