Originally posted by Leonhard
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in ice cores recovered from Greenland glaciers. Each successively deeper ice layer represents a snapshot of Earth's climate history from the past, and together, the oxygen isotope record told a story of abrupt, millennial-scale climate shifts in air temperatures over Greenland between extremely cold stadial conditions and relatively mild interstadial periods during the last ice age (Figure 1) (Alley 2000, Alley et al. 2003). There are twenty-five of these distinct warming-cooling oscillations (Dansgaard 1984) which are now commonly referred to as Dansgaard-Oeschger cycles, or D-O cycles. One of the most surprising findings was that the shifts from cold stadials to the warm interstadial intervals occurred in a matter of decades, with air temperatures over Greenland rapidly warming 8 to 15°C (Huber et al. 2006). Furthermore, the cooling occurred much more gradually, giving these events a saw-tooth shape in climate records from most of the Northern Hemisphere
There are cycle that explain the Ice Age. There's a big one about the wobble of the Earth's rotation which is more than ten thousand year long called the Milankovich Cycle. It explains a very slow, periodic temperature variation. It can't however explain the sudden rise in temperature since the seventies. CO2 driving a greenhouse effect can however.
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