Implications of delayed participation and technology failure for the feasibility, costs, and likelihood of staying below temperature targets-Greenhouse gas mitigation scenarios for the 21st century

According to our analysis, significant delay in the participation of major emitters leads to the unattainability of the most stringent forcing targets. Moreover, delayed participation may lead to excessive additional global mitigation cost that may even exceed the mitigation costs of the most stringent forcing targets in the best case with full participation. We find that for countries that significantly delay their participation, the early gains from postponing mitigation may be offset to a large extent in the long-term, due to the need for more pronounced mitigation later in the century. Linking the radiative forcing targets with temperature change, we find that the chances of staying below certain temperature thresholds may be significantly lower over the course of the century than would be by looking exclusively at 2100. From a policy perspective our results therefore suggest that focusing on early abatement to avoid significant overshoot of concentrations may be as important as the long-term concentration target itself.