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The graph above shows 420,000 years of ice core data from Vostok, Antarctica research station
The sequence forms a sawtooth wave form
http://en.wikipedia.org/wiki/Milankovitch_cycles
NEW RESEARCH AUGUST 2013
Insolation-driven 100,000-year glacial cycles and hysteresis of ice-sheet volumeAyako Abe-Ouchi, Fuyuki Saito, Kenji Kawamura, Maureen E. Raymo,Jun’ichi Okuno, Kunio Takahashi & Heinz Blatter
August 2013
-statistical tests have demonstrated that the glacial cycles are indeed linked to eccentricity, obliquity and precession cycles
– Yet insolation alone cannot explain the strong 100,000-year cycle, suggesting that internal climatic feedbacks may also be at work
-The responses of equilibrium states of ice sheets to summer insolation show hysteresis ….with the shape and position of the hysteresis loop playing a key part in determining the periodicities of glacial cycles
– C02 is not the driver of the 100,000 yr cycle
THe feedback process and loop is described in the abstract
http://www.nature.com/nature/journal/v500/n7461/full/nature12374.html
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Thanks to this website for the notification of this research
http://theresilientearth.com/?q=category/blog-tags/ice-age
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Another article on this same topic but paywalled at SCIENCE
How to Make a Great Ice Age, Again and Again and Again
Richard A. Kerr
For more than 30 years, climate researchers have been trying to figure out how slight changes in Earth’s orbit could drive the great ice ages. Now the best computer model of the ice ages yet may have found the answer:
a rhythmic stretching of Earths egg-shaped orbit around the sun every 100,000 years amplifies the influence of a second orbital cycle.