The warm Cretaceous climate - Role of the long-term carbon cycle

An annual energy-balance model is coupled to a steady state formulation of the long-term CO2 cycle to investigate the possible sources of global warming of the Cretaceous period. It is found that paleogeography solely is an insufficient factor but that the different latitudinal distribution of continental masses 100 My ago influenced the CO2 cycle and favored a larger content of the atmospheric CO2 level. A larger rate of tectonic activity and the possible influence of the vegetation in a CO2 richer atmosphere provide further sources of atmospheric carbon dioxide increase. The combination of these factors, together with a more vigorous poleward heat transport, provides CO2 levels 5 to 15 times larger than today and a global surface warming within the 6-1 C estimated from paleoindicators.