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1 Environmental Change Research Centre, Department of Geography, University College London, 26 Bedford Way, London WC1H 0AP, UK mmaslin{at}geog.ucl.ac.uk
2 Department of Earth and Ocean Sciences, The University of British Columbia, 6339 Stores Road, Vancouver, British Columbia V6T 1Z4, Canada
The mid-Pleistocene revolution (MPR) is the term used to describe the transition between 41 ka and 100 ka glacial-interglacial cycles which occurred about one million years ago. Despite eccentricity having by far the weakest influence on insolation received at the Earth’s surface of any of the orbital parameters, it is often assumed to be the primary driver of the post-MPR 100 ka climate cycles. The traditional solution to this is to call for a highly nonlinear response by the global climate system to eccentricity. This ‘eccentricity myth’ is a simplified view of the relationship between global climate and orbital forcing and is in part due to an artefact of spectral analysis. Our aim here is to clarify the often confused role of eccentricity and review current theories of the MPR. We suggest that the post-MPR ‘100 ka’ glacial-interglacial cycles are more closely linked to precession, with the saw-toothed climate cycles being defined by every four or five precessional cycle. Because control over the number of precessional cycles involved is determined by eccentricity, eccentricity at most paces rather than drives the system. If true, then one must also question whether the MPR, itself defined by an abrupt change in spectral characteristics, is not also somewhat misconceived.
