The Milankovitch (26/41/100,000-year) Cycles

Attempts have been made to explain the Ice Age cycles in terms of the combined effects of the cyclical variations of the Earth's orbit, such as, the changing eccentricity of the Earth's orbit around the Sun in 100,000-year cycles, and the 26,000-year cycles of the precession of the Earth's spin axis, and the 41,000-year cycles of the changing tilt of the spin axis. All of these factors affect the relative distribution of the sunlight energy received by the Earth in the different hemispheres, and also the intensity of the seasons (termed solar forcing). 

Since the computed combined effect of these cycles (the Milankovitch Cycles) somewhat matches the Ice Age cycles, it had been assumed for a long time that these orbital factors are the causes for the Ice Age cycles. However, the Universe doesn't quite comply with computed predictions. Too many irregularities have been observed. In one case an interglacial began 10,000 years in advance of the computed causes. Here we have a case of an effect, preceding a cause. Evidently the impossibility invalidates underlying failures in assumptions.

ice age glaciation cycles with the Milankovitch cycles added

The most immediate example of the observed non-compliance of the universe with computed solar forcing is the missing reflection of the current weaker solar forcing that has already dropped way below the level that has prevailed for most of the deep cold period of the last glaciation cycles (see the light-blue line), for which we should experience deep glaciation right now. But since this hasn't materialized, a fourth factor is evidently superimposed that is more deeply causative, and may in fact be causative of the orbital variations. 

We are presently at a low point in solar forcing, or solar exposure (expressed in the above diagram in watts per square meters at the top of the troposphere at 65 North in latitude). The current low value was only rarely reached and crossed below during the historic glaciation cycles that we have ice core records for. According to this conditioning, the Earth should be in a glaciation zone right now, in terms of the Milankovitch Cycles. Since we haven't entered the glaciation zone yet, we might be in the boundary zone right now, towards it. This means the time has come to get ready to protect our agriculture, our prime food source, in the most efficient manner possible.