Differentiation of future commitments in climate policy

The Framework to Assess International Regimes for the differentiation of commitments (FAIR) is used to explore the implications of two possible climate regimes: (1) increasing participation (i.e. a gradual increase in the number of Parties involved and their level of commitment according to participation and differentiation rules) and (2) ?Contraction and Convergence? with universal participation and a convergence of per capita emission permits. It is found that in a regime of Increasing participation, stabilising the CO₂ concentration at 450 ppmv by 2100 requires participation of major developing countries before 2050 in global emission control, irrespective of the participation and differentiation rules chosen. In the case of stringent climate targets, a convergence regime seems to provide more incentives for a timely participation of developing countries, and opportunities for an effective and efficient regime for controlling global emissions than Increasing participation.