[CPOSharky]

...changes in Earth's orbit.

Really?

[ClearCase_guy]

It's the oscillation of the orbit that really confuses me. Maybe -- maybe -- ice sheets could perturb our orbit. But once the ice sheets disappear, would the orbit "spring back" to it's original path? And could that be done repeatedly over many thousands of years?

I'm thinking that a law of Thermodynamics is being violated here with orbital paths oscillating despite no energy change being recorded.

[gleeaikin]

But let’s not forget the probable North American boloid(s) around 13,000 years ago that may have caused the Younger Dryas. I suspect there are no simple or single answers. SC, time to post the Firestone et al book.