Politically Feasible Emissions Targets to Attain 460 ppm CO2 Concentrations

A new climate change treaty must address three current gaps: the absence of emissions targets extending far into the future; the absence of participation by the United States, China, and other developing countries; and the absence of reasons to expect compliance. Moreover, to be politically acceptable, a post-Kyoto treaty must recognize certain constraints regarding country-by-country economic costs. This article presents a framework for assigning quantitative emissions allocations across countries, one budget period at a time, through a two-stage plan: (a) China and other developing countries accept targets at business-as-usual (EMU) levels in the coming budget period, and, during the same period, the United States agrees to cuts below BAU; (b) all countries are asked to make further cuts in the future in accordance with a formula that includes a Progressive Reductions Factor, a Latecomer Catch-up Factor, and a Gradual Equalization Factor. An earlier proposal (Frankel 2009) for specific parameter values in the formulas achieved the environmental goal that carbon dioxide (CO2) concentrations plateau at 500 ppm by 2100. It met our political constraints by keeping every country's economic cost below thresholds of Y=1 percent of income in Present Discounted Value, and X=5 percent of income in the worst period. The framework proposed in this article attains a stricter concentration goal of 460 ppm CO2 but only by loosening the political constraints.