Causes and timing of future biosphere extinction

We present a minimal model for the global carbon cycle of the Earth containing the reservoirs mantle, ocean floor, continental crust, biosphere, and the kerogen, as well as the aggregated reservoir ocean and atmosphere. The model is specified by introducing three different types of biosphere: procaryotes, eucaryotes, and complex 5 multicellular life. We find that from the Archaean to the future a procaryotic biosphere always exists. 2 Gyr ago eucaryotic life first appears. The emergence of complex mul-ticellular life is connected with an explosive increase in biomass and a strong decrease in Cambrian global surface temperature at about 0.54 Gyr ago. In the long-term future the three types of biosphere will die out in reverse sequence of their appearance. We 10 show that there is no evidence for an implosion-like extinction in contrast to the Cam-brian explosion. The ultimate life span of the biosphere is defined by the extinction of procaryotes in about 1.6 Gyr.