You talk about the evidence that "the maximum CO2 concentration never went above 300 ppm." that was went there was an ice sheet, so we have to believe that there was ALWAYS and ice sheet over the entire Earth, even when the Earth was on giant continent, Pangaea [sic] I believe, that located around the equator.
These Ice Sheets also "flowed" south from the Poles. That would seem to indicate that it was colder up north then toward the equator, other wise the ice sheets should have build evenly.
"Science isn't democratic", it is eco-nomic.