The effect of silicate weathering on global temperature and atmospheric CO₂

Abstract

Models of the carbon cycle, used to calculate atmospheric CO 2 levels and mean global surface temperatures over geologic time, rely heavily on estimates of CO 2 consumed by chemical weathering. Weathering of calcium and magnesium silicates is the primary sink for atmospheric CO 2 , yet alkali feldspar dissolution rates or data from carbonate aquifers have generally been used as model inputs instead. The latter causes calculated CO 2 levels and temperatures to be anomalously high in the model of Berner et al. (1983) (for example, temperatures of 24°C and 19°C are calculated for the Cretaceous and Eocene, respectively). When Ca and Mg silicate weathering rates are used as primary inputs instead, ambient temperatures and atmospheric CO 2 levels are calculated to be significantly closer to recent preindustrial levels (global mean temperatures of ∼20.5°C and 17.5°C in the Cretaceous and Eocene, respectively), indicating an appreciably tighter coupling between chemical weathering and climate.