Japan

Historical emissions data were obtained from the UNFCCC GHG inventory and cover the period from 1990 to 2021 submitted in Common Reporting Format (Government of Japan, 2023a). The submission to the UNFCCC is supplemented by the National Inventory Report data file, which provides sector level emissions after allocation of electricity-related emissions to end-use sectors (Government of Japan, 2023b).

The target emission level in 2030 provided in the updated NDC submitted in October 2021 is directly used in this assessment.

The Japanese government provides no underlying assumptions on its 2050 net-zero GHG target. For this reason, we assumed that GHG emissions will balance LULUCF sinks in 2050. We estimate the LULUCF sink for 2050 to be 28–61 MtCO₂e using a 10-years historical average between 2009–2019 (upper bound estimate) and a 10-years trend projection towards 2030 based on the period between 2009–2019 that we keep constant towards 2050 (lower bound estimate).

Energy-related CO₂ emissions

For the analysis of current policy projections, we used the IEA World Energy Outlook (WEO) 2023 Stated Policies Scenario (STEPS) as a basis (IEA, 2023). The WEO STEPS reflects both implemented policies as well as announced policies (see Annex B.6 of WEO 2023); only for the power sector the electricity mix targets of the updated NDC and the 6th Strategic Energy Plan (METI, 2021c) were assumed to be fully achieved.

Since it is premature to assume that the 2030 electricity mix targets would fully be achieved, we explored different shares of renewable and nuclear power generation based on historical trends, estimates by external studies, and current status of nuclear reactor safety examinations. CO₂ emissions from the power sector were re-calculated based on the low and high emission electricity mix cases described below.

In the low emissions case, we assumed that:

• The WEO2023 STEPS scenario projections will be fully achieved, which means that:
  • Nuclear power generation share will reach 20%, the lower range of the 2030 target. The nuclear capacity in operation will reach 30 GW, which will be larger than the total of 25 reactors that have applied for restart and two reactors under construction that applied for future operation to the Nuclear Regulation Authority as of March 2024 (JAIF, 2024).
  • Coal and oil power shares are kept to the NDC target (coal: 19%, oil: 2%).
  • Renewable electricity generation reaches 385 TWh/year in 2030. The resulting share in total generation is 37 %, thus reaching the 36-38 % target.
  • Gas power share is at 20%.

In the high emissions case, we assumed that:

• All 27 reactors that have applied for restart (or future start of operation for plants under construction) as of March 2024 will be in operation by 2030 but only at the capacity factor of 49% (the 2021 level), taking into account the possible court cases and unplanned inspections. The resulting share in total generation is 11%.
• Oil power shares kept to the NDC target (2%).
• Renewable energy share reaches 315 TWh/year in 2030, based on the reference scenario for Japan included in the 2022 APEC Energy Demand and Supply Outlook (APEC, 2022). The resulting share in total generation is 30%, falling short of the 36-38% target.
• Gas and coal power meets the remaining demand with equal shares, leading to 26% share each.

After the recalculation of the 2030 electricity mix, CO₂ emissions in 2030 were recalculated— CO₂ emission factors per technology were assumed to be identical to those in the WEO 2023 STEPS.

Other emissions

The projections for Industrial process CO₂ emissions were based on the growth rates between 2020 and 2030 from the IEA WEO 2023 STEPS, multiplied by the 2020 emissions from the UNFCCC GHG inventory (Government of Japan, 2023b; IEA, 2023).

Agricultural & waste CO₂ emissions were extended to 2030 using the trend of emissions intensity per GDP and per capita between 2011-2021 (UN DESA, 2022; World Bank, 2023).

Other non-CO₂ emissions were extended to 2030 using the trend of emissions intensity per GDP and per capita between 2011-2021 (UN DESA, 2022; World Bank, 2023).

For F-gas emissions, the expected impacts of the Act on Rational Use and Proper Management of Fluorocarbons (2013 amendment) to enhance management of F-gas use as well as the Ozone Layer Protection Act (‘F-gas Act’, 2018 amendment) to regulate the production and imports of F-gases to comply with the Kigali Amendment were considered. Our calculations show that the HFC emission levels are projected to fall far short of the levels targeted under the updated NDC.

As described in the current policy projections section, the F-gas Act has not been successful in improving the recovery rate of refrigerants from end-of-life refrigeration and air conditioning equipment which was 41% against the targeted rate of 50% in 2020 (METI & MOEJ, 2021b). The recovery rate even dropped to 40% in 2021 (MoEJ, 2022). Based on the historical trends reported by MOEJ (MoEJ, 2022), we assume that the HFC recovery rate will not improve over time. We also assume that the leakage rates for the in-use stock will also not improve under current policies. Regarding the 2018 amendment of the Ozone Layer Protection Act, the business-as-usual consumption levels are projected to be below the Kigali cap at least until 2025 (METI, 2018a): the Kigali cap for Japan becomes significantly lower only in 2029. Since there is some time lag between consumption and emissions, we assume that the amended Ozone Layer Protection Act will not affect the HFC emission levels up to 2030.

The point of departure for the revised F-gas emission projections is the business-as-usual (BAU) projections provided in the background document of the Plan for Global Warming Countermeasures (MOEJ, 2016a) – the Plan projects F-gas emissions to increase from 39 MtCO₂e/year in 2013 to 77 MtCO₂e/year in 2030 under a BAU scenario. The three measures: (i) enhanced recovery from end-of-life equipment, (ii) avoidance of leakage from in-use equipment, and (iii) switch to lower GWP F-gas and non-F-gas refrigerants are expected to reduce emissions to the NDC target level of 29 MtCO₂e/year in 2030. In our assessment, we assume that only part of the NDC implementation plan, i.e. the switch to lower GWP F-gas and non-F-gas refrigerants, would be achieved.

The CAT uses Global Warming Potential (GWP) values from the IPCC's Fourth Assessment Report (AR4) for all its figures and time series. Assessments completed prior to December 2018 (COP24) used GWP values from the Second Assessment Report (SAR).