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'The Day After Tomorrow', Q&A Response

 

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How rapid is rapid?

NASA: The cooling took around 200 years to occur, but the warming was faster (on the order of decades).

NSIDC: The figure below shows the evidence for rapid climate change in the Northern Hemisphere at the end of the last ice age, and the climate since then, as it is preserved in an ice core from central Greenland. It shows a record of temperature (measured by oxygen isotope ratios-- a chemical 'thermometer'-- preserved in the snow), and the amount of snow that fell each year.

The figure also shows just how large the change was from the past ice age to our present climate -- and, more importantly, how stable the past ten thousand years have been relative to the ice ages. In fact, nowhere in the ice core record of the past several hundred thousand years can a period of such stability be found. Even so, the relatively small shifts in this period had noticeable effects. The figure illustrates two well-known recent shifts in climate: the Little Ice Age, when the Thames River routinely froze in winter, thick enough to skate upon; and the Medieval warm period, coinciding with the 'Camelot' legends.

All of civilization, from the development of agriculture and the invention of cities, to the Space Shuttle and the Internet, has occurred during the most stable period in the climate record of the past 400,000 years.


Climate changes in central Greenland over the last 17,000 years. Reconstructions of temperature and snow accumulation rate (Cuffey and Clow, 1997; Alley, 2000) show a large and rapid shift out of the ice age about 15,000 years ago, an irregular cooling into the Younger Dryas event, and the abrupt shift toward modern values. The 100-year averages shown somewhat obscure the rapidity of the shifts. Most of the warming from the Younger Dryas required about 10 years, with 3 years for the accumulation-rate increase. A short-lived cooling of about 6°C occurred about 8,200 years ago (labeled 8ka event). Climate changes synchronous with those in Greenland affected much of the world.
(Image provided with permission by the National Academy Press, from the report 'Abrupt Climate Change: Inevitable Surprises (2002)'. Copyright © 2003. National Academy of Sciences. All rights reserved. 500 Fifth St. N.W., Washington, D.C. 20001.)




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