Multi-stage: A rule-based evolution of future commitments under the climate change convention

This article presents the regional emission targets corresponding to different climate regimes for differentiating commitments beyond 2012 on the basis of the Multi-Stage approach. This approach assumes a gradual increase in the number of Parties involved and their level of commitment according to participation and differentiation rules. The analysis focuses on two global greenhouse gas emission profiles resulting in CO₂-equivalent concentrations stabilising at 550 and 650 ppmv in 2100 and 2150, respectively. Three Multi-Stage cases have been developed in order to assess different types of thresholds. These share three consecutive stages representing different commitments: stage 1 - no quantitative commitments; stage 2 emission-limitation targets and stage 3 - emission reduction targets. The analysis shows that by 2025 all three cases result in emission reduction objectives for all Annex I regions of at least 30-55% below their 1990 levels for 550 ppmv, whereas for 650 ppmv target they range from 0 to 20%. Furthermore, early participation is required of the major non-Annex I regions through emission limitation targets i.e. before 2025 and 2050 for the 550 and 650 ppmv targets, respectively. The first participation threshold for adopting emission-limitation targets on the basis of a capability-responsibility index (as introduced here) can provide for a balanced and timely participation of non-Annex I regions. Major strengths and weaknesses of the climate regimes are discussed and important obstacles and pre-conditions for their feasibility and acceptability are highlighted.