Authors: Yin Long,Yoshikuni Yoshida, Haoran Zhang, Heran Zheng, Yuli Shan, Dabo Guan.

Journal: Scientific Data (2020) 7:233.

In the wake of the Fukushima nuclear disaster, Japan largely moved away from nuclear power generation and turned back towards an energy sector dominated by fossil fuels. As a result, the pace towards reaching emission reduction targets has largely slowed down. This situation indicates that higher emissions will continue to be generated if there is no appropriate and efficient measurement implemented to bridge the energy demand gap. To contribute adequate mitigation policies, a detailed inventory of both CO2 emissions and socioeconomic factors, both at the national and regional level, should be issued. Thereby, this work contributes to a time-series emission with a record of 47 prefectures in Japan as well as their associated socioeconomic features. The compiled emission inventory is based on three major fossil fuels and 26 sectors with careful emission allocations for regional electricity generation. This dataset is uniformly formatted and can be expected to provide vital information to set regional reduction allowances and sectoral reduction priorities.

Background and Summary

Greenhouse-gas emissions (GHGs) are already committing the planet to likely climate changes in the next 20 years1, with fossil fuel combustion expected to release the most substantial amount of GHGs. Over the past few decades, the international community has adopted a series of commitments and agreements aimed at achieving sustainable development through cross-boundary collaboration2. These include the Kyoto Protocol with quantified targets for reductions in emissions of GHGs set for each Annex I Parties respectively; and for Paris Agreements reached in 2015, aiming to achieve net-zero emission of anthropogenic GHGs by the second half of this century, which has come up with different national reduction goals and is expected to contribute to the international goal as a whole. As one of the most developed countries, Japan has ratified the Paris Agreement and has pledged an absolute reduction in its emissions by 26.0% by fiscal year (FY) 2030 (Compared with FY2013), which is one of the ambitious climate pledges from intended nationally determined contributions (INDCs)3–6. However, in the wake of the 2011 Fukushima nuclear disaster, Japan largely moved away from nuclear power generation and turned towards an energy sector dominated by fossil fuels (See Appendix Figs. 1 and 2). The adverse consequences following the disaster increase the difficulty of reaching the reduction target. Within two years of the Fukushima nuclear disaster, Japan’s national emission reached 1410 million tons of CO2 equivalent (Mt-CO2eq) in FY 2013, which reached 2.0% increase based on the FY2005. In the FY2017, the total GHGs of Japan is estimated as 1,292 Mt-CO2eq, with 90% of emissions found to be carbon dioxide (CO2)7. Undoubtedly, the Fukushima nuclear accident shows the weakness of Japan’s energy mix and has evolved into an obstacle for future social decarbonization. Given this, Japan has been the subject of worldwide focus concerning its resilience from disaster and the secondary GHGs increase.

On the other hand, given the essential role of emission accounting, an emission inventory enables follow-up research to come up with social decarbonization actions from a multi-disciplinary perspective. Quantification of fossil fuel CO2 emissions at high space and time resolution is emerging as a critical need in carbon cycle and climate change research8. Furthermore, sub-national inventories are vital for various levels of decision-making9–11, prioritizing reductions12,13 and volume targets14. There is an extensive body of literature on emission accounting at regional level15,16, or to a lesser extent at prefectural17, city-level18–23 or higher resolution supported by remote sensing technology8. Previous efforts demonstrate that a detailed scale of inventory will enhance our understanding of regionality and spatial heterogeneity, which has been emphasized in previous sub-national accounting studies9,10,12,24–26. These studies demonstrate a recent trend toward sub-national emission accounting, which manifest in increasing attention on the societal demand for detailed emission information9,27–29.

Therefore, to realize the reduction targets by FY2030 and promote an efficient reduction mechanism in the long-term, a means of accurate emission accounting is the first, as well as an essential, step to achieving the decarbonization target. Given this, previous studies have tried to analyze regional energy consumption and discussion of regional emission responsibility by a single year in Japan. However, the system boundary varied by research target and data availability with inconsistent estimates, which would be likely to lead to misleading conclusions30–32. The discrepancy among different fiscal years cannot now support a continuous observation of regional energy and emissions.

In Japan, the Ministry of the Environment (MoE) and the National Institute for Environmental Studies (NIES) have released Japanese National Greenhouse Gas Emissions data by each fiscal year. Similarly, the International Energy Agency (IEA) and Carbon Dioxide Information Analysis Centre (CDIAC) also provide national scale GHG emissions of Japan, but they vary from each other’s estimation. Furthermore, according to our observations in previous estimates, all the existing emission inventories only present Japan’s total CO2 emissions, with regional emission details missing. There is scarcely any emission database constructed according to detailed sectors for Japan and its 47 prefectures. Furthermore, there is no comprehensive emission and socioeconomic dataset which keeps unified sectoral classification.

To bridge to this data gap, the dataset firstly estimated by this study presents the CO2 emission inventory by three major fossil fuel for 25 sectors (Except Electricity sector), according to regional sectoral energy consumption statistics. In this data, the three emission sources are then classified as non-power use coal, non-power use crude oil and non-power use natural gas. The Electricity sector is estimated separately according to electric company and power plant data. Thus, the total prefectural emission of 26 sectors can be generated. In addition, the socioeconomic dataset is constructed by unified format and constant price of 2011. This dataset can be easily utilized by both national and regional emission structure analysis and the driving force tracking it.

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