This Proceedings of the National Academy of Science report presents a framework for allocating a global carbon reduction target among nations through a gradual convergence of emission caps and floors.
The 1992 United Nations Framework Convention on Climate Change (UNFCCC) created a 2-tier world. It called upon the developed countries to "take the lead'' in reducing carbon emissions, and, under the principle of "common but differentiated responsibilities,'' established no time frame for developing countries to follow. However, a consensus is now emerging in favor of low stabilization targets. These targets cannot be achieved without the participation of developing countries, which today emit about half of global CO2 emissions and whose future emissions increase faster than the emissions of industrialized countries under ‘‘business as usual'' scenarios.
On what terms should developing countries participate? There are many proposals, each buttressed by some appeal to "fairness.'' Per capita allocation is widely acknowledged to represent the only equitable goal in the long term, but intermediate steps are required in the short-to-medium term. Uniform percentage reductions in emissions across all countries are rightly rejected by all parties, on the grounds that industrialized countries must create headroom for developing countries. Here, we offer a different approach: An allocation of national targets for fossilfuel CO2 emissions derived from a fairness principle based on the "common but differentiated responsibilities'' of individuals, rather than nations. Our proposal moves beyond per capita considerations to identify the world's high-emitting individuals, who are present in all countries.