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oC Target and Mitigation in Japan in 2050

As shown in Fig. 4.1 from IPCC (2014), in order to achieve the 2 oC target, the global GHG emissions in 2050 would be 41–72 % compared to the 2010 level. Since the G8 Summit at Heiligendamm in 2007, the global leaders have shared the long-term vision that the GHG emissions in 2050 should be half compared to the present level. If GHG emission per capita is equal among the world in 2050, it becomes around 2 tCO2. In the case of Japan, the present emission level is around 10 tCO2. That is to say, the GHG emissions per capita should be 80 % reduction to achieve the 2 oC target.

In the 4th Environmental Basic Plan endorsed by the Cabinet in 2012, the longterm GHG emission mitigation target was made clear. The target in 2050 is 80 % reduction of GHG emissions. In the following sections, the possibility of 80 % reduction of GHG emissions is examined. The quantitative results are based on Kainuma et al. (2014) for the report of the Deep Decarbonization Pathways Project (DDPP). DDPP is organized by the Sustainable Development Solutions Network (SDSN) and the Institute for Sustainable Development and International Relations (IDDRI), and 15 countries including Japan and international organizations join this project. The interim report was opened at the Climate Summit in 2014. For more information, please see IDDRI and SDSN (2014).

Table 4.2 History of GHG emission mitigation in Japan and the world

Table 4.2 (continued)

How to Achieve 80 % Reduction Target in Japan

As shown in the explanation of the 4th Environmental Basic Plan, the mitigation target in 2050 is set to be 80 % reduction. In order to assess the 2050 target, we utilized the AIM/Enduse to disaggregate Japan into 10 regions. The treated technologies are the same as the analyses for 2020 and 2030 using the national model, and the treatment of future is also the same, that is to say, recursive dynamics. On the other hand, the features of this model are that the local renewable energy potential can be reflected, interconnected line of electricity among the regions can be assessed, and so on.

Other important assumptions are nuclear power and carbon capture and storage (CCS). As regards the nuclear power, the following are the main assumptions:

• Lifetime is limited to 40 years for plants built in 1990 and 50 years for all other plants, and from 2013 to 2035, an additional three GW nuclear plants capacity is included based on the premises of New Policies Scenario of the World Energy Outlook 2013 (IEA 2013).

• Subject to these assumptions and maximum capacity factor of 70 % for all plants, electricity generation from nuclear plants represents about 50 TWh in 2050.

As for the CCS, the following assumptions are set:

• Geologic carbon storage potential.

• Complying with previous studies, CCS technologies are assumed to be available in 2025, and annual CO2 storage volume is assumed to increase up to 200 MtCO2/year in 2050.

In the illustrative scenario, the primary energy supply and demand in 2050 decreases to almost half compared to the 2010 level as shown in Fig. 4.7. In 2050, renewables and fossil fuels with CCS account for more than 50 % of primary energy supply. In the power sector, the nuclear power is assumed to be phased out gradually, and electricity generation from coal without CCS is entirely phased out by 2050. Renewable energy is developed over the midto long terms and reaches approximately 59 % of total electricity generation through large-scale deployments of solar PV and wind power. In addition, natural gas (equipped with CCS) is developed to ensure balancing of the network and reaches about a third of total electricity generation in 2050. Carbon intensity of electricity falls to nearly zero in 2050 as shown in Fig. 4.8. And also, in the final energy demand sector, the energy intensity will be improved, and electricity will be the dominant energy over the long term. As a result, the long-term GHG emission reduction target in 2050 will be reached as shown in Fig. 4.9.

The alternative pathways are also investigated using the same model. In the “without nuclear power scenario,” an 80 % emission reduction in 2050 is still feasible. However, higher carbon intensity is experienced during the transition period. The impact of nuclear phaseout as compared to the illustrative scenario is

Fig. 4.7 Energy pathways by source

Fig. 4.8 Drivers of decarbonization

Fig. 4.9 CO2 emission of illustrative scenario from 2010 to 2050

relatively small in the long term, given the small share of nuclear energy in 2050 in any case. Another alternative scenario is “less CCS scenario,” in which CO2 storage volume is assumed to be limited to 100 MtCO2/year. Achieving long-term emission reduction target proves to be still feasible with substantial increase of renewable energy, particularly solar PV and wind power. The share of renewable energy in electricity supply reaches approximately 85 % in 2050, and variable renewable energies account for about 63 % in electricity generation in 2050, hence imposing a further challenge for integration into the electricity system.


In this chapter, the historical change of the emission reduction target in Japan and the possibility of 80 % reduction in 2050 in Japan are represented. The feature of mitigation target in Japan is mainly based on the bottom-up approach. That is to say, the process stressed the feasibility of the target. On the other hand, the top-down decision is also requested for the ambitious reduction target.

From the previous estimations, even in Japan, there are still many reduction potentials. Toward the achievement of 2 oC target, taking actions with the longterm perspective becomes more important.

Acknowledgment The research in this chapter is supported by the Environment Research and Technology Development Fund by the Ministry of the Environment, Japan (2-1402).


GIO (2014) Japan's national greenhouse gas emissions in fiscal year 2012 (Final figures).

GIO (2015) Japan's national greenhouse gas emissions in fiscal year 2013 (Final figures).

IDDRI and SDSN (2014) Pathways to deep decarbonization, 2014 report. content/uploads/2014/09/DDPP_Digit_updated.pdf

IEA (2013) World energy outlook 2013. OECD/IEA, Paris

IPCC (2013) Climate change 2014: The physical science basis. Cambridge University Press, Cambridge and New York

IPCC (2014) Climate change 2014: mitigation. Cambridge University Press, Cambridge and New York

Kainuma M, Oshiro K, Hibino G, Masui T (2014) Japan chapter of pathways to deep

decarbonization, 2014 report. report_Japan_chapter.pdf

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