Walker et al. (1981) described a simple planetary thermostat based on the rate of carbon drawdown from the ocean-atmosphere system being linked to the rate of degassing from the solid Earth via continental chemical weathering. This geological carbon cycle thermostat rapidly became the accepted model and since then this has become a standard way to think about changes in ocean chemistry (e.g., through variable continental weathering inputs) and biogeochemical cycles (e.g., through continental weathering nutrient fluxes). This talk will explore whether this model is consistent with observational constraints, and whether existing constraints allow alternative models to be tested. The evolution of Cenozoic climate, from greenhouse to icehouse, and seawater chemistry will be used as a test case.

Walker, J.C.G. et al, 1981. A negative feedback mechanism for the long-term stabilization of Earth’s surface temperature. JGR. 86, 9776–9782.