Overdue-glaciation

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The overdue-glaciation hypothesis is a theory proposed by William Ruddiman that the end of the current interglacial warm period is already overdue; that is, according to astronomical models that have successfully characterized the pattern of past glaciations due to variations in the earth's orbit known as Milankovitch cycles, the next ice age should have already started a few thousand years ago. In his Early anthropocene hypothesis Ruddiman proposes that the scheduled arrival of the next ice age was forestalled by intense farming and deforestation by early farmers that began raising the level of greenhouse gases eight thousand years ago.

The overdue-glaciation hypothesis has been challenged on the grounds that comparison with an earlier interglaciation ("Stage 1", 400,000 years ago) suggest that 16,000 more years must elapse before the current Holocene interglaciation comes to an end, and that thus the early anthropogenic hypothesis is invalid. But Ruddiman argues that this results from a false alignment of recent insolation maxima with insolation minima from the past, among other irregularities which invalidate the criticism.

Orbital calculations by Berger and Loutre ^[1] seem to indicate that the current interglacial period may last an unusually long time, perhaps another 50,000 years or so.