Temporal and spatial distribution of global mitigation costs: INDCs and generation equity

Each country’s Intended Nationally Determined Contribution (INDC) pledges an emission target for 2025 or 2030. Here, we evaluated the INDC emission pathway’s inter- and intra- generational equity by comparing the INDC pathway with an immediate emission reduction pathway by using AIM/CGE (Asian-pacific Integrated Model/Computable General Equilibrium). The results showed that, as compared with an immediate emission reduction pathway, the inter-generational equity status for INDC and post-INDC emission pathways is not favorable and the future generation suffers more from mitigation. Moreover, this conclusion was robust to the inequality aversion parameter of the discount rate. On the other hand, the INDC pathway has better intra-generational equity in the early part of the century than does the immediate emission reduction pathway with uniform carbon price across countries. However, intra-generational equity worsens later in the century. We suggest that an additional 20% emissions reduction in the INDCs would improve both inter- and intra-generational equity as compared to the current INDCs. We also suggest that countries should commit to more emissions reductions in the follow-up INDC communications and that continuous consideration for low-income countries is needed for global climate change cooperation after 2030.