claim: The killer proof that CO2 does not drive climate is to be found during the Ordovician- Silurian and the Jurassic-Cretaceous periods when CO2 levels were greater than 4000 ppmv ( parts per million by volume ) and about 2000 ppmv respectively.
evidence: The Jurassic (  / dʒʊˈræs.ɪk /  juu-RASS-ik; from the Jura Mountains ) is a geologic period and system that spanned 56 million years from the end of the Triassic Period 201.3 million years ago ( Mya ) to the beginning of the Cretaceous Period 145 Mya.