Development of common socio-economic scenarios for climate change impact assessments in Japan

Abstract. Climate change is one of the greatest long-term challenges faced by humanity. In the projection of climate change impacts, scenarios based on assumptions regarding future conditions are commonly used. Shared socio-economic pathways (SSPs) are widely employed as socio-economic scenarios for global-scale predictions. The SSPs provide future projections of population and gross domestic products. However, SSPs are not suitable for detailed assessments for a country such as Japan, as they include only global regional data. The S-18 project aims at a nationally unified projection of climate change impacts across multiple sectors in Japan. In contribution to this, based on the previous study for Japan SSPs, we established common socio-economic scenarios designated as Japan SSP1, Japan SSP5, and status quo. Japan SSP1 and Japan SSP5 are based on qualitative links to global SSPs. Japan SSP1 foresees sustainable society with low-carbon emission, while Japan SSP5 envisions a society dependent on fossil fuels, emitting large amounts of greenhouse gases. The status-quo scenario assumes no future change based on the current conditions in Japan. Moreover, we provided a common dataset of population and land-use under these scenarios. Population data were obtained from existing population projections, and land-use data were estimated according to population changes and current land-use classifications. Here, the dataset prepared for the S-18 project is detailed and possibilities for its improvement discussed.