Japan's long-term climate mitigation policy: Multi-model assessment and sectoral challenges

TLDR

Japan is the sixth largest greenhouse gas emitter and a key player in meeting the Paris Agreement, with its 2050 goal of an 80 % emissions cut hinging on a major energy system transition. The paper examines energy‑related CO₂ emissions by analyzing decarbonization scenarios that align with Japan’s government targets. Six energy‑economic and integrated assessment models are used to uncover the challenges of achieving these decarbonization goals. The results indicate that high marginal abatement costs, a large industrial energy share and residual emissions, and significant transport decarbonization hurdles together suggest that both energy and industrial policies must be addressed, with costs potentially exceeding those of negative‑emissions technologies and highlighting the need for further model development.

Abstract

Japan is the sixth largest greenhouse gas emitter in 2016 and plays an important role to attain the long-term climate goals of the Paris Agreement. One of the key policy issues in Japan's energy and environmental policy arena is the energy system transition to achieve 80% emissions reduction in 2050, a current policy goal set in 2016. To contribute to the ongoing policy debate, this paper focuses on energy-related CO2 emissions and analyzes such decarbonization scenarios that are consistent with the government goals. We employ six energy-economic and integrated assessment models to reveal decarbonization challenges in the energy system. The modeling results show that Japan's mitigation scenarios are characterized by high marginal costs of abatement. They also suggest that the industrial sector is likely to have a large final energy share and significant residual emissions under the 80% reduction scenario, though it is generally thought that the transport sector would have large decarbonization challenges. The present findings imply that not only energy policy but also industrial policy may be relevant to the long-term environmental target. Given the high marginal costs exceeding those of negative emissions technologies that could place a cost ceiling, further model development would be crucial.