Mid-century emission pathways in Japan associated with the global 2 °C goal: national and global models’ assessments based on carbon budgets

This study assesses Japan’s mid-century low-emission pathways using both national and global integrated assessment models in the common mitigation scenario framework, based on the carbon budgets corresponding to the global 2 °C goal. We examine high and low budgets, equal to global cumulative 1600 and 1000 Gt-CO₂ (2011–2100) for global models, and 36 and 31 Gt-CO₂ (2011–2050) in Japan for national models, based on the cost-effectiveness allocation performed by the global models. The impacts of near-term policy assumption, including the implementation and enhancement of the 2030 target of the nationally determined contribution (NDC), are also considered. Our estimates show that the low budget scenarios require a 75% reduction of CO₂ emissions by 2050 below the 2010 level, which is nearly the same as Japan’s governmental 2050 goal of reducing greenhouse gas emissions by 80%.