The study surveys the literature on the economic costs of climate policy in different countries and world wide. Studies of costs to achieve national targets on emissions are partly based on bottom-up approaches, where the availability of new, or alternative, technologies is emphasized. These indicate that emissions of carbon dioxide (CO2) may be reduced by up to 50% in some countries at low, sometimes negative costs. Top-down studies tend to indicate higher costs, at least in developed countries. A 10% reduction in CO2 emissions within the next 15 to 20 years is expected to result in a reduction ranging from 0.5% to 1.5% in GDP. Due to the impact of assumptions on the results, it is difficult to compare the costs among countries. Most cost-benefit analyses of climate change policies prescribe only very moderate action now. This depends to some extent on the expected damage caused by climate change. The most significant factor for the assessment of benefits is, however, the choice of discount rate. There is little consensus about the proper choice of this rate. Funding: The Norwegian State Pollution Control