Image:Milankovitch Variations.png

From Global Warming Art

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Description

Image showing the pattern of deglaciation during the last five glacial terminations. In particular, note that temperature rise begins in advance of changes in carbon dioxide, which is consistent with an externally forced system.

This figure shows the variations in Earth's orbit, the resulting changes in solar energy flux at high latitude, and the observed glacial cycles.

According to Milankovitch Theory, the precession of the equinoxes, variations in the tilt of the Earth's axis (obliquity) and changes in the eccentricity of the Earth's orbit are responsible for causing the observed 100 kyr cycle in ice ages by varying the amount of sunlight received by the Earth at different times and locations, particularly high northern latitude summer. These changes in the Earth's orbit are the predictable consequence of interactions between the Earth, it's moon, and the other planets.

The orbital data shown is from Quinn et al. (1991). Principal frequencies for each of the three kinds of variations are labeled. The solar forcing curve (aka "insolation") is derived from July 1st sunlight at 65 °N latitude according to Jonathan Levine's insolation calculator [1]. The glacial data is from Lisiecki and Raymo (2005) and gray bars indicate interglacial periods, defined here as deviations in the 5 kyr average of at least 0.8 standard deviations above the mean.

Though Milankovitch himself (and others before him) considered orbital changes as a possible explanation for changes in glaciation, the modern believe in this theory was largely advanced by Hays et al. 1976.

Copyright

This image was produced by Robert A. Rohde from publicly available data.

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References

[DOI] Hays, J. D., John Imbrie, and N. J. Shackleton (1976). "Variations in the Earth's Orbit: Pacemaker of the Ice Ages". Science 194 (4270): 1121 - 1132.
[abstract] [full text] [DOI] Lisiecki, L. E., and M. E. Raymo (2005). "A Pliocene-Pleistocene stack of 57 globally distributed benthic δ¹⁸O records". Paleoceanography 20: PA1003.
Quinn, T.R. et al. "A Three Million Year Integration of the Earth's Orbit." The Astronomical Journal 101 pp. 2287-2305 (June 1991).