Historical emissions data were obtained from the UNFCCC GHG inventory and cover the period to 2017 (UNFCCC, 2019).
Pledges and targets
Target emission level for 2020 was calculated from 2005 emissions data according to Japan’s Second Biennial Report to the UNFCCC (Government of Japan, 2015). We calculated Japan's LULUCF accounting quantities in 2020 for afforestation, reforestation and deforestation based on the accounting rule under the second commitment period of the Kyoto Protocol. Net removal by forests (38 MtCO2e/yr) is taken into account for 2020.
The target for 2030 was calculated using Japan’s NDC and the UNFCCC GHG inventory data submitted in 2019 (UNFCCC, 2019).
Current policy projections
Energy-related CO2 emissions
For the analysis of current policy projections, we used the IEA World Energy Outlook (WEO) 2019 Current Policies Scenario (CPS), which covers various climate related policies implemented as of 2018 and their impact on energy-related CO2 emissions as a basis (IEA, 2019). The GDP for 2030 assumed in the IEA WEO 2019, based on World Bank and International Monetary Fund estimates, is 19% lower than that assumed in the NDC.
The WEO foresees a relatively large share of electricity generation from nuclear energy in 2030 (17%). While this is overachieved by the current assumptions of the government (Basic Energy Plan), it is not completely supported by the rate of restart of currently shut down nuclear power plants. We explored “high nuclear” and “limited nuclear” scenarios:
We do not use “With measures” emissions projection provided in Japan’s Third Biennial Report (BR3) as reference. The BR3 “With measures” scenario is an NDC achievement scenario, which takes into account, not only the policy measures already implemented in FY2013, but also those to be implemented by FY2030 (Government of Japan, 2017). The assumed GDP growth rates are also very high—on average 1.7% per year for 2013-2030 based on the government's growth target (METI, 2015).
For the full nuclear restart scenario, it is assumed that all 25 nuclear reactors (plus two allowed to resume construction) that applied for restart as of November 2019 will be approved and complete their extended 60-year lifetime (with an average 6500 hours/yr operation, comparable to about 6400 hours/yr assumed in IEA WEO 2019’s Current Policies Scenario). For the two reactors under construction, the Ohma reactor is assumed to start operating in 2026 and the Shimane No. 3 reactor in 2020. The changes in nuclear power generation compared to the IEA WEO 2019’s Current Policies Scenario is balanced by coal and gas power. The ratio of coal and gas power converges to 1:1 by 2030 and the average capacity factor of nuclear power plants is assumed to be 80%.
For the limited nuclear scenario, it is assumed that only 15 reactors that were allowed to restart as of November 2019, after additional safety measures were implemented, would be in operation up to 2030 (some with a 60-year extended lifetime) but at a much shorter 3250 hours/yr operation on average, taking into account the possible court cases and unplanned inspections. The electricity supply gap is filled by renewables and fossil fuel power (coal and gas power)—the ratio between renewables and fossil fuel power remains the same as in IEA WEO 2019 and the ratio between coal and gas power converges to 1:1 by 2030.
After the recalculation of the 2030 electricity mix, CO2 emissions were calculated— CO2 emission factors per technology were assumed to be identical to those in the WEO 2019 CPS. Finally, the growth rates of energy-related CO2 emissions up to 2030, recalculated based on the IEA WEO 2019 CPS, were applied to the 2017 historical energy related CO2 reported in the national GHG inventory report submitted to the UNFCCC.
For the emissions of non-energy CO2, CH4 and N2O, we assumed that the intensity of these emissions per unit GDP will reduce linearly towards 2030, following the historical trends observed between 2010 and 2017. The GDP growth projections up to 2030 were taken from IEA (IEA, 2019).
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 and 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 also considered. Our calculations show that the HFC emission levels are projected to fall far short of the levels targeted under the NDC (Government of Japan, 2015; MOEJ, 2012b; MOEJ & METI, 2014).
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 in 2017 was only 38% (METI; MOEJ, 2019). Based on the historical trends reported in METI and MOEJ (METI; MOEJ, 2019), we assume that the HFC recovery rate will not improve over time (40% for 2020-2030). 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, 2018b); 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/yr in 2013 to 77 MtCO2e/yr 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/yr 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.
Global Warming Potentials
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).