Options for differentiation of future commitments in climate policy: how to realise timely participation to meet stringent climate goals?

This paper aims at exploring options for differentiation of future commitments in global greenhouse gas emissions control, linked to climate targets. This is done on the basis of theEUtarget of a maximum global temperature increase of 2°C compared to pre-industrial levels. 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) '<italic>contraction and convergence</italic>' (C&C) 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.