The Mid‐Cretaceous Super Plume, carbon dioxide, and global warming

Carbon‐dioxide releases associated with a mid‐Cretaceous super plume and the emplacement of the Ontong‐Java Plateau have been suggested as a principal cause of the mid‐Cretaceous global warming. We developed a carbonate‐silicate cycle model to quantify the possible climatic effects of these CO₂ releases, utilizing four different formulations for the rate of silicate‐rock weathering as a function of atmospheric CO₂. We find that CO₂ emissions resulting from super‐plume tectonics could have produced atmospheric CO₂ levels from 3.7 to 14.7 times the modern pre‐industrial value of 285 ppm. Based on the temperature sensitivity to CO₂ increases used in the weathering‐rate formulations, this would cause a global warming of from 2.8 to 7.7°C over today's global mean temperature. Altered continental positions and higher sea level may have been contributed about 4.8°C to mid‐Cretaceous warming. Thus, the combined effects of paleogeographic changes and super‐plume related CO₂ emissions could be in the range of 7.6 to 12.5°C, within the 6 to 14°C range previously estimated for mid‐Cretaceous warming. CO₂ releases from oceanic plateaus alone are unlikely to have been directly responsible for more than 20% of the mid‐Cretaceous increase in atmospheric CO₂.