billy, I guess I should have included reference to the other cycles identified by Milankovitch. Milankovitch identified the eccentric orbital cycle of 100,000 years, the axis tilt cycle of 42,000 years, and the wobble cycle of the axis over 25,800 years. He discovered that when they coincided in a certain way, that could be correlated to events such as ice ages. Obviously with such odd cycles, 100,000, 42,000, and 25,800 years, there are countless different ways they can affect the levels of solar radiation reaching earth, never exactly repeating their impact the previous time they coincided in a similar fashion. And that is not accounting for any yet unidentified forces that also influence our planet. What is it that causes the earth's orbit to vary as it does. There must be some other outside forces that also vary over time.
