An increase in temperature accelerates the chemical processes of weathering reducing the amount of carbon in the atmosphere. 1 the global surface temperature is plotted under increase of the solar luminosity for the whole history of the Earth. In contrast to the curve for fixed CO 2 content of the atmosphere the temperature is always above the freezing point of water. The role of the biosphere is to increase the weathering rate. A short description of the model used can be found here .
S denotes the corresponding solar luminosity in solar units.
Due to their different albedos the local temperatures differ from each other. The growth rates depend only on the local temperature. Because the global albedo of the planet is changed by the growth process, the global temperature is changed altering the growth rates. One interesting aspect is the behaviour of the coupled vegetation-climate model on external perturbations, e.g., an increase of the external solar luminosity. T 0 is the global temperature of the corresponding planet without vegetation.