Some countries, like Norway and Sweden, long ago introduced a tax on CO2 emissions to reflect a social cost of $100 per ton, or even higher. Many private companies, including major oil firms, have also recently introduced an internal accounting cost of carbon emissions to guide their decisions regarding fossil-fuel investments.
挪威和瑞典等一些国家早已引入了二氧化碳排放税，其税率所反映的社会成本为每吨100美元甚至更多。包括主要石油企业在内的许多私人公司最近也引入了内部碳排会计成本指导有关化石燃料投资的决策。这样做可以让公司预测未来政府监管的财务后果。