The distribution and magnitude of emissions mitigation costs in climate stabilization under less than perfect international cooperation: SGM results

The EMF22 Transition Scenario subgroup explores the implications of delayed accession on limiting climate change to various radiative forcing levels. This paper focuses on the cost of limiting radiative forcing and the role that industrial leakage plays in scenarios of delayed accession. We find that delayed participation shifts the cost burden toward regions that take early action and away from regions that undertake mitigation later. However, the inefficiencies introduced by delay are so great that present discounted costs are higher in the delayed scenario for regions that delay as well as for regions taking early actions. An important element of these inefficiencies is industrial emissions leakage, that is non-participating regions increase their emissions relative to the reference case. In aggregate, industrial leakage rates are less than 10% if all regions of the world begin emissions mitigation by 2050-higher in carbon-intensive sectors and lower in low-carbon-intensity sectors. Additionally, we consider the implication of technology on carbon prices, the feasibility of limiting radiative forcing to low levels, and the incentives to overshoot the radiative forcing limit.