Using the Milankovitch Theory to Date Sea Cores
The Milakovitch theory, which postulates that small changes in the Earth’s orbit around the sun are the triggers for the various ice ages or glaciations, has become the dominant paradigm in scientific circles. The orbital variations are fairly well documented and they do lead to a very small change in the way that solar radiation is partitioned to the Earth at different latitudes. They don’t lead to any change in the amount of overall radiation however.
Lacking any other plausible trigger for the radical weather changes that would lead to an ice age, it has become accepted to the point that many scientists see it more as a fact than assumption. In other words, they believe that the small changes in radiation distribution might cause an ice age, and knowing that the orbital variations are cyclic coupled with the assumption of billions of years , they thus deduce many ice ages.
Since they believe that the orbital variations caused the weather changes, and they assume that the changes in oxygen 18 to 16 recorded in sea cores are due to those climate changes, they date the sea cores by the orbital cycles (Imbrie, et al, 531). They then use the sea core dates to validate the entire theory. This seems a little like circular reasoning to me, but I’m just a woodcutter.
Imbrie, J., et al
Milankovitch Theory viewed from Devils Hole, Nature 363, p 531, 1993