Japan has set greenhouse gas emissions reduction targets for 2030 and 2050, as stated in the nationally determined contribution (NDC) and in the long-term strategy for decarbonization (LTS) submitted to the UNFCCC in 2020, respectively. While upgrading these targets is needed to realize the global climate goals (2 °C and 1.5 °C), the implications of the target for the period in-between remains unclear. This study assesses the energy and macroeconomic impacts of enhancing the ambition of 2040 and 2050 emission reduction targets in Japan by means of a computable general equilibrium (CGE) model. In addition, we analyze the implications on the speed of energy efficiency improvement and low-carbon energy penetration along with macroeconomic impacts, and the shift from the current LTS goal (80% emissions reduction by 2050) to a full decarbonization one. The study shows that, compared to the current ambition (53% reduction by 2040 compared to 2005), enhancing ambition of the 2040 (63% reduction by 2040 compared to 2005) and 2050 targets (zero emissions by 2050) rises the share of low-carbon energy supply more drastically than the decreases in energy intensity, and increases macroeconomic costs by 19–72%. Moreover, meeting these targets demands accelerating considerably the reductions in carbon intensities through expansion of renewables and CCS beyond historical trends and beyond current efforts towards the 2030s NDC. Enabling larger low-carbon supplies and energy efficiency improvements makes full decarbonization by 2050 possible at costs equivalent to current ambition. Further analyses are needed to clarify at a finer detail the implications of changes in these enablers by sectors, technologies and policies. This kind of analysis offer key insights on the feasibility of Japan’s emission reduction targets for the formulation of new commitments for the next cycle of the Global Stocktake under the Paris Agreement.

日本分别设定了2030年和2050年的温室气体减排目标，这分别在国家自主贡献（NDC）和2020年向UNFCCC提交的长期脱碳战略（LTS）中进行了阐述。为了实现全球气候目标（2°C和1.5°C），需要对这些指标进行升级，但该指标在此期间的影响仍不清楚。这项研究通过可计算的一般均衡（CGE）模型评估了日本实现2040年和2050年减排目标的雄心壮志对能源和宏观经济的影响。此外，我们分析了对提高能源效率和低碳能源渗透的速度以及宏观经济影响的意义，以及从当前的LTS目标（到2050年减少80％的排放量）到完全脱碳的目标。研究表明，与当前的目标相比（到2040年，与2005年相比减少53％），增强2040年的目标（与2005年相比，到2040年减少63％）和2050年的目标（到2050年实现零排放）增加了低排放量的份额。碳能源的供应比能源强度的下降要大得多，并使宏观经济成本增加了19％至72％。此外，要实现这些目标，就需要通过扩大可再生能源和CCS的速度，大大加快碳强度的降低速度，这要超过历史趋势和当前为实现2030年代NDC所做的努力。启用更多的低碳能源供应并提高能源效率，到2050年完全脱碳成为可能，而成本却与目前的目标相当。需要进行进一步的分析，以更详细地阐明这些推动因素的变化对各部门的影响，技术和政策。这种分析为日本制定减排目标的可行性提供了关键见解，从而为《巴黎协定》下一个全球清单评估的新周期制定新的承诺。