No, it was caused by wooly mammoths burping and farting.
No, you are wrong. The global warming of 55 million years ago was caused by the previous race of humans (the Ancients) who existed then. They burnt fossil fuels (without regard to the environment) with these huge bonfires to keep the T-Rex's and Raptors away.
Certain very liberal Ancients said it was better to get eaten by T-Rex than despoil the planet. In a rigged election, the liberal Ancients won, put out the bonfires, and sure enough the ancients got eaten, except for the redneck Ancients who survived (Homo Arkansas).
This is why the first human-like fossils found are ape-like. Only the redneck Ancients reproduced, and they were hairy, had big eye-brow ridges and intermarried with their kinfolk. They would have fit in well on the Ancient's version of Jerry Springer. Anyway, the redneck Ancients destroyed their own gene-pool and we all regressed to little furry critters and had to re-evolve.
parsy, who is sorta warm right now.