usa sets more than 5000 winter records!, page-18

gm, yes you're correct, they are both not correct. I'll clarify. The 6Ma camps hypothesis can fit within that proposed by the 70Ma camp. The 6Ma camp disputes the 70Ma determination.

So if the question is 'Can the available data accommodate both hypothesis?' the answer is yes.

pintohoo, if you mean that we can have shorter cold periods within longer warm periods in the global sense. The yes we can. Though there needs to be a forcing to get the climate there.

With respect to the Milankovitch Cycles the general concept that people hold is that you get periods where the orbital and rotational cycles coincide to produce long periods of low solar insolation (measure of incoming incident solar radiation - independent of solar intensity) that equate to glacial periods and periods of higher solar insolation that relate to interglacial periods.

Now that is not entirely correct. The Earth has two stable climate states. Ice Age/Glacial and Interglacial. Once in one of these two states the relative forcings maintain the status quo. What the Milankovitch Cycles do is create relatively short periods of either anomalously high or low solar insolation that tips the climate into the opposite state. Once tipped into a stable state it will bob about that level until forced again to the other state.

The previous glacial/interglacial cycle has generally been every 100,000 years. This hasn't always been the case, prior 400,000 years ago the period was around 40,000 years.

They can model the changes in the orbital and rotational parameters quite accurately into the past and into the future 10's of millions of years. With that data they can correlate many of the historic temperature anomalies with insolation.

Interestingly going forward it shows that the Earth is entering a period where the Earth's orbit becomes quite circular and less elliptical. And as such will not likely have the required insolation to tip the Earth into the next ice age for 10's of thousands of years and possibly half a million years. Regardless of the effects of the current atmospheric CO2

http://amper.ped.muni.cz/gw/articles/html.format/orb_forc.html

http://geosci-webdev.uchicago.edu/~archer/reprints/archer.2005.trigger.pdf