Vortragender: Univ.-Prof. Dr. Alfred Greiner (Univ. Bielefeld) Abstract:We analyze the interrelation between anthropogenic global warming and economic growth where private agents are assumed to be rational. The government levies a tax on output and a tax on greenhouse gases that are an external effect from producing goods. Assuming a basic growth model the effects of varying the tax rates are analyzed as concerns economic growth, economic welfare and as concerns the rise in average global surface temperature. Using simulations, it is demonstrated that higher emission taxes may both raise economic growth and welfare while reducing the extent of global warming. In addition, situations exist where a rise in emission taxes reduces economic growth but raises welfare. In the social optimum, economies with cleaner technologies have fewer emissions than economies with less clean production technologies. This holds because economies with cleaner technologies invest relatively more in abatement than economies with less clean technologies. In an extension of the model we allow for feedback effects in the climate system. We first study the model assuming that abatement spending is fixed exogenously and demonstrate with the use of numerical examples that the augmented model may give rise to multiple equilibria and thresholds. In this case, the question of to which equilibrium the economy converges crucially depends on the climate sensitivity and on the date when a significant reduction of greenhouse gas emissions starts. Next, we analyze the social optimum where both consumption and abatement are set optimally and show that the long-run equilibrium is unique in this case.