Japanese energy policies have integrated climate change from the 1990’s. This orientation was formalized by the signing of the Kyoto Protocol in 1997 which committed Japan to reduce its GHG emissions by 6% between 1990 and 2012  [2]. However, its disengagement of the Protocol for the second period 2013-2020 raised doubt as to its ability to be a "global climate leader". In addition, the Fukushima nuclear accident in March 2011 has changed the direction of the energy mix towards more polluting fossil fuels. Europe hoped, however, that Japan would present an ambitious policy to reduce GHG emissions in the context of the COP 21, but its proposed proposal to reduce them of only 25.4% between 2005 and 2030, unveiled in late April 2015, caused a huge disappointment. Even if this goal is not revised upwards, Japan will make an important contribution to COP 21 through its technologies and original experiences.

The change in the post-Fukushima energy revolution

In June 2010, the Government of the Democratic Party of Japan had adopted a "strategic energy plan" to push through between 2010 and 2030 the share of nuclear power in the energy mix from 29% to 50% and those of renewable energy from 10 % to 20% in order to reduce dependence on imported fossil fuels. About a year after the nuclear accident in Fukushima, the Government announced its objective to phase out nuclear energy by 2040.

To compensate for the power generation deficit, it was decided to develop renewable energy, including solar. The ten major regional power companies, owners of electrical networks, had to buy solar energy at a high rate (40-42 yen / kWh). However, the rapid resolution of power shortages led to an increase in production of thermal power plants which caused a rise in consumption of fossil fuels. Furthermore, awareness campaigns for citizens and industries in the energy sobriety were launched in parallel with programs to support optimization of energy efficiency technologies. Between 2010 and 2013, nearly half of the missing nuclear capacity was filled by energy conservation (energy efficiency and sobriety) [1].

The return of nuclear power with Abe

Electricity production was 88% dependent on fossil fuels when Shinzo Abe took office in late 2012. This dependency was a concern for the trade balance, running a deficit since 2011, but also for energy security threatened by geopolitical instability of oil and natural gas supplying regions or routes (Middle East, Strait of Hormuz and Malacca ...). Moreover, the price of electricity had increased  [2]. If GHG emissions of the electricity sector had increased by 16% between 2010 and 2012, total emissions of Japan had remained close to the level reached in 2007.

In February 2015, the METI (Ministry of Economy and Foreign Trade) revealed some figures on energy self-sufficiency goal in 2030 (24.3% against 6.3% in 2012) and desired electricity energy mix. The solution of the return to nuclear power is favored. Although the share of renewable energy is to double, fossil fuels would still have a preponderant weight even if Japan intends to reduce the dependency on coal in power plants.

In 2030, the share of nuclear power in the energy mix could reach 20% to 22%. The answer to the constraints of energy self-sufficiency and greenhouse gas emissions as well as the need to lower the price of electricity explain the government will to return to nuclear energy although the Japanese population is still predominantly against it. According to calculations of METI, while nuclear power would cost 10.1 yen / kWh in 2030, hydro-electricity would reach 11.0 yen, solar 12.5 -16.4 yen, wind electricity 13.9 -21.9 yen and geothermal 19.2 yen [3] . Given the limits to the development of hydropower, nuclear power appears to be very competitive [4] . However, as the objective of the share of nuclear in 2030 exceeds existing operational capacities, it will be necessary to build new nuclear reactors and / or extending the life of nuclear plants beyond the 40 years determined by the law [5] . While at the end of May 2015, there was still no active nuclear reactor despite the green light from the Nuclear Regulation Agency granted to three plants, the central Sendai 1 of the Kyushu Electric could be the first to restart in late July 2015. However, the return to nuclear energy risks breaking the growth dynamic of renewable energy.

By 2030, the government plans to increase the share of renewable energy in electricity generation to 24% which is nearly double the average level from 2000 to 2010  [6]. While in 2010, hydropower accounted for 3% of the energy consumption and 8.5% of the production of electricity; other renewable energies contributed to respectively 1% and 1.1%. Fukushima was a catalyst to the development of renewable energy. Thus, Japan became in 2013 the second largest investor after China. His efforts were focused on solar with installed capacity increasing from 2.5 GW to 23 GW between 2010 and the end of 2014. However, in late 2014, the State has reduced the volume of compulsory purchase of solar energy by power companies and lowered the solar energy purchase price to 27 yen / kWh. At such price, the solar sector investments become unprofitable especially since power companies are starting to buy less solar energy. This policy shift threatens to derail the rise of the Japanese solar energy while nuclear power could jeopardize the development of all renewable energies.

Owing to carbon credit purchases and planting forests, Japan has fulfilled its commitment to Kyoto Protocol by displaying a GHG reduction of 6% between 1990 and 2012. As the probabilities of an upward revision of its proposal to reduce GHG emissions by 25.3% between 2005 and 2030 for COP 21 are low, it will not be a leader in this area compared to the EU (-40% of emissions) or even the United States (- 26% to -28% between 2005 and 2025). Although the post-Fukushima fallout explain the weakness of Japanese objectives, a more ambitious long-term policy vision was expected from the fifth world GHG emitter. Japan can still contribute very positively to the COP 21 with its technological edge in the areas of energy efficiency, solar and hydrogen. Its experiences of energy sobriety and decentralized energy saving projects under the leadership of local actors (smart grids, 10-year plan to decarbonise the city of Tokyo  [7]) are all interesting leads.
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