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National-level climate actions will be vital in achieving global temperature goals in the coming decades. Near-term (2025–2030) plans are laid out in Nationally Determined Contributions; the next step is the submission of long-term strategies for 2050. At present, national scenarios underpinning long-term strategies are poorly coordinated and incompatible across countries, preventing assessment of individual nations’ climate policies. Here we present a systematic and standardized, yet flexible, scenario framework varying 2050 emissions to build long-term national energy and climate mitigation scenarios. Applying the framework to six major Asian countries reveals individual challenges in energy system transformation and investment needs in comparable scenarios. This framework could be a starting point for comprehensive assessments as input to the Global Stocktake over the coming years., 世界各国の2050年の温室効果ガス削減目標を分析するための国際的な研究フレームワークの提案. 京都大学プレスリリース. 2021-05-28., Pathways to global climate targets. 京都大学プレスリリース. 2021-06-01.

Japan’s mid-century strategy for reducing greenhouse gas emissions by 80% in 2050 would require large-scale energy system transformation and associated increases in mitigation costs. Nevertheless, the role of energy demand reduction, especially reductions related to energy services such as behavioral changes and material use efficiency improvements, have not been sufficiently evaluated. This study aims to identify key challenges and opportunities of the decarbonization goal when considering the role of energy service demand reduction. To this end, we used a detailed bottom-up energy system model in conjunction with an energy service demand model to explore energy system changes and their cost implications. The results indicate that final energy demand in 2050 can be cut by 37% relative to the no-policy case through energy service demand reduction measures. Although the lack of carbon capture and storage would cause mitigation costs to double or more, these economic impacts can be offset by energy service demand reduction. Among energy demand sectors, the impact of industrial service demand reduction is largest, as it contributes to reducing residual emissions from the industry sector. These findings highlight the importance of energy service demand reduction measures for meeting national climate goals in addition to technological options.

Electric power demand management will play an important role in the creation of smart-energy communities. We are conducting a field experiment on the real-time feedback of electric power consumption via smart meters and tablet PCs with the participation of 51 households on Nushima Island, one of Japan's remote islands. Our estimate of the effect of feedback in reducing power demand by panel data analysis has revealed that such feedback achieves a saving of 7.6 percent in electric power demand.

In order to realize a low-carbon society (LCS), it is necessary to formulate a comprehensive policy consisting of a large number of “options” (i.e., policies as well as technical and behavioral measures). Based on the concept of backcasting, this paper proposes a methodology and a model, called the backcasting model (BCM), that organizes a system of various LCS options and projects their detailed schedule toward a given target year. The methodology and model mainly focus on describing a complex system of LCS options and the consistency of their schedule. Other aspects such as the costs of LCS measures, stock dynamics of technologies, and effects of economic instruments are not explicitly considered. To permit quantitative treatment of various types of options, they are classified into several categories. The BCM calculates the schedule of the options under given quantitative information on the options and relationships between them. The methodology and model were applied to Kyoto City as an example. First, a quantitative snapshot of socioeconomic status and greenhouse gas (GHG) emissions was described. In the snapshot, a 45% reduction of GHG emissions compared with 1990 was achieved with moderate economic growth. The BCM was applied to about 130 options shown in an action plan of the Kyoto Municipal Government, and a schedule of the options was calculated. This methodology treats wide-ranging and complex low-carbon options in a quantitative and consistent manner and supports the policymaking process toward the realization of a low-carbon society.

Although several central and local governments around the world have set long term low-carbon targets, they do not always have concrete plans toward the goals. In order to reduce greenhouse gas(GHG) emission significantly, various kinds of measures in various sectors will be required. Some measures reduce GHG emissions directly and are called “direct measures” in this study. To implement those direct measures by the target year, indirect measures are also required, such as economic incentives, regulations, and urban planning. This study proposes a method to develop a concrete long-term schedule of direct and indirect measures, a “roadmap,” based on the idea of backcasting. To formulate the implementation of and relations between measures, and to estimate the concrete schedule to achieve the targets, we developed a model called “backcasting tool” (BCT). Given the information of measures including GHG emission reduction by measures, required resource input and maximum total resource input, and so on, BCT estimates the progress of the measures from the current to the target year. The method was applied in Kyoto City with a low-carbon target, 40% reduction in CO 2 emission from fossil fuel by 2030 compared with 1990. Using BCT, we showed that a detailed schedule consists of about 100 measures classified into six fields. The result shows it is possible to achieve the target if all the measures, both direct and indirect, are implemented in time.