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.