This paper summarizes the debate on the costs and benefits of regional and global action to reduce future emissions of greenhouse gases. The paper also presents new evidence on possible future global emissions of carbon dioxide from burning fossil fuels where these emissions are disaggregated by major developed and developing country regions. The basis of the projections is a global simulation model called the G-Cubed model. Given these projections of future emissions, the model is used to estimate the size of carbon taxes necessary to stabilize emissions within each region in the year 2000 at the levels of emissions in 1990. It is shown that the costs of stabilizing carbon dioxide emissions vary across countries when each country stabilizes its own emissions at a 1990 level. These differences in costs reflect differences in the energy intensity of production, differences in the source of energy generation, differences in projections of population growth and different projections of productivity growth.