[en] The obstacles to bringing about consumer response to environmental dangers are particularly challenging for global problems like ozone depletion and the greenhouse effect. In this situation, there is the danger of what is commonly termed the tragedy of the commons, the ecological destruction that can occur from uncontrolled use of shared resources like the atmosphere. There is probably no country for which reductions in global warming provide an adequate economic incentive to reduce greenhouse gas emissions unilaterally, even though such action could yield substantial global benefits. From any one country's viewpoint, the costs of controlling emissions may exceed the benefits since, without international agreement, reductions achieved by one nation may be offset by another. Therefore, even though the entire world may be better off as a result of efforts to lower emissions, new economic incentives are necessary to lead the market to a socially efficient outcome. This paper describes the range of domestic and international policies that could be adopted to reduce emissions of greenhouse gases, and also discusses the results of modeling analyses of government actions that could reduce or increase such emissions