Milankovitch cycles graph

Paleoclimatologists Rock -Two million years of radical climate change is significant.

David C. Greene writes:

"The smoking gun of the ice ages" is the title of an article in the Dec. 9, 2016 issue of Science, the journal of the American Association for the Advancement of Science. The author, David A. Hodel, is listed with the Laboratory for Paleoclimate Research, Department of Earth Sciences, at Cambridge University in the UK.

Hodel cites a 40-year-old paper in Science, 194,1121 (1976). In that paper, Hays, Imbrie and Shackleton reported that their proxies for paleo sea surface temperatures and changing continental ice volumes exhibited periodicities of 42,000, 23,500 and 19,000 years, matching almost exactly the predicted orbital periods of planetary obliquity, precession and eccentricity. They also found that the dominant rhythm in the paleoclimate variations was 100,000 (±20,000) years.

Other climatologists have identified 20 glacial/interglacial oscillations over the past two million years with glacial parts of the cycles lasting about four times as long as the warm, interglacial parts. The last glacial maximum was about 18,000 years ago. We have been enjoying the present warm interglacial for about 12,000 years.

Milankovitch cycle
At glacial maxima, sea levels have been about 400 feet below present sea levels and sea surface temperatures about nine degrees C (14.4 degrees F) lower than present temperatures. The movement and conversion of 400 feet of ocean water to ice located in the higher latitudes required large and long-lasting influence from outside the Earth. The persistence and the magnitude of the above-described changes cannot logically be ascribed to mankind's combustion of fossil fuels. Furthermore, in the terminations of the glacial eras, rising temperature preceded rises of CO2 by several centuries, absolving CO2 as the cause of the preceding temperature rise.

I cannot identify the cause(s) of the Earth's quasi-repeatable climate excursions during the past two million years. However, the data provided by the paleoclimatologists makes sense to me as a physicist with three semester-hours of astronomy. My candidate for responsibility is an orbital influence on the amount of energy Earth received from the Sun as the Sun slowly danced around the center of mass of the entire solar system, with Jupiter being the weightiest of the Sun's planetary dancing partners.