As well, and to use Alex's phrase Historic Climate Change (HCC), there was an HCC that started about 40 million years ago and that was the first Ice Age.
Earth scientists have studied this and have concluded these started as a result of the collision of the tectonic plate on which India floats with the plate on which southern Asia floats resulting in the creation of the Himalaya mountains. This upthrust of land very high into the atmosphere altered air circulation patterns.
BTW this pertains to my last previous post about tilt. Not sure if I posted this earlier so 'repeat' it:
http://www.livescience.com/forcesofn...arth_tilt.html