A reader writes: where is the paleontological data showing the correspondence between CO2 levels and ice age events?. The answer is, all over the place; here is one possible source. The correspondence isvery good.
At this point, the s(k)eptics jump up and down and say, aha, but the T leads the CO2. To which the answer is, so what? The lead is small (on the scale of these things: maybe 800y) and hard to even measure (you certainly can’t see it on the scale of that graph). We *know* it takes feedbacks between T and CO2 to create the ice age cycles, which because of their periodicity are presumed to have orbital forcing as their ultimate pacemaker.