Colloquium: Martin Heimann

Why do the global carbon emissions have to be reduced to near zero in order to stabilize the atmospheric CO2 concentration and its climate impact? Why is there a limited “carbon budget” for keeping the global temperature increase below a prescribed value? Answering these questions requires a mathematical model of the global carbon cycle - climate system linking carbon emissions to atmospheric CO2 concentrations and the global temperature. How simple can such a model be in order to be mathematically understandable to the informed lay person while still capturing the first-order dynamics of the global carbon cycle - climate system? In this talk I examine some simple (published) models and try to identify the essential principles any simplified global carbon cycle model must incorporate, as well as the critical observational tests it must meet to be considered reliable.