Assessing the effort sharing for greenhouse gas emission reductions in ambitious global climate scenarios

To reinforce the long-term commitment to climate change mitigation, the post-2012 climate policy framework is aimed to be completed by 2009. The new agreement needs to include a wider participation of parties, and therefore needs to address the effort sharing of countries. The mitigation capabilities and the responsibilities of countries do however vary significantly. This can, in principle, be overcome with a cap-and-trade system, with which the question of equity is addressed trough the allocation of emission allowances. A number of effort sharing schemes have been proposed. Effort sharing however suffers from a fundamental trade-off between detail and transparency on how the emission allocations are calculated. This study addresses this problem by comparing and combining the results from a transparent but simplified effort sharing model EVOC, and a detailed and - due to its complexity - seemingly non-transparent ETSAP-TIAM energy system model. The aim of the study is to evaluate the goodness of the initial effort sharing, particularly in terms of mitigation costs experienced by different regions in the scenarios. Based on the long-term energy-climate scenarios crafted with the TIAM model, we assess the resulting consequences in emission profiles and the energy system, concentrating especially on regional mitigation costs and emission trading. Two cases of market failures in emission trading are also considered. Finally we compare the mitigation potentials between the two models and estimate the effect of EVOC recalibration on the national emission allowances. The results of the study underline particularly the importance of detailed and reliable assumptions for the mitigation potentials of different countries in the effort sharing process.