100,000-year problem

δ18O, a proxy for temperature, for the last 600,000 years (an average from several deep sea sediment carbonate samples)[a]

The 100,000-year problem (also 100 ky problem or 100 ka problem) of the Milankovitch theory of orbital forcing refers to a discrepancy between the reconstructed geologic temperature record and the reconstructed amount of incoming solar radiation, or insolation over the past 800,000 years.[1] Due to variations in the Earth's orbit, the amount of insolation varies with periods of around 21,000, 40,000, 100,000, and 400,000 years. Variations in the amount of incident solar energy drive changes in the climate of the Earth, and are recognised as a key factor in the timing of initiation and termination of glaciations.

While there is a Milankovitch cycle in the range of 100,000 years, related to Earth's orbital eccentricity, its contribution to variation in insolation is much smaller than those of precession and obliquity. The 100,000-year problem refers to the lack of an obvious explanation for the periodicity of ice ages at roughly 100,000 years for the past million years, but not before, when the dominant periodicity corresponded to 41,000 years. The unexplained transition between the two periodicity regimes is known as the Mid-Pleistocene Transition, dated to some 800,000 years ago.

The related 400,000-year problem refers to the absence of a 400,000-year periodicity due to orbital eccentricity in the geological temperature record over the past 1.2 million years.[2]

The transition in periodicity from 41,000 years to 100,000 years can now be reproduced in numerical simulations that include a decreasing trend in carbon dioxide and glacially induced removal of regolith, as explained in more detail in the article Mid-Pleistocene Transition.[3]


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  1. ^ Raymo, Maureen E.; Nisancioglu, Kerim H. (2003). "The 41 kyr world: Milankovitch's other unsolved mystery". Paleoceanography. 18 (1): 1011. Bibcode:2003PalOc..18.1011R. doi:10.1029/2002PA000791. S2CID 17640098. All serious students of Earth's climate history have heard of the '100 kyr problem' of Milankovitch orbital theory, namely the lack of an obvious explanation of the dominant ~100 kyr periodicity in climate records of the last 800,000 years.
  2. ^ Huggett, Richard J. (2006). The natural history of the Earth : debating long-term change in the geosphere and biosphere. London: Routledge. ISBN 0-203-00407-8. OCLC 77059125.
  3. ^ Brovkin, V.; Calov, R.; Ganopolski, A.; Willeit, M. (April 2019). "Mid-Pleistocene transition in glacial cycles explained by declining CO2 and regolith removal". Science Advances. 5 (4): eaav7337. doi:10.1126/sciadv.aav7337. PMC 6447376. PMID 30949580.