One of the glaring differences worthy of note is the rarity of ice caps in the Arctic Circle during the planetary ice ages. The current ice age is the first time the Earth has seeen such an extensive glaciation of the Northern hemisphere since the Cryogenean. Why this has not been nore alaring in the scientific community is a bit odd, when you consider the potential consequences to the biosphere.
http://www.bbc.co.uk/news/science-environment-15749757 you might want to read through this one ~