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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 CO2 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. [ABSTRACT FROM AUTHOR]

In this paper we draw up future roadmaps for technologies, policies, and optimal investment timing toward the achievement of a low-carbon society (LCS) in Japan by 2050. Future pathways for Japan to follow are calculated using an analytical model based on a backcasting methodology. Early actions can lead to pathways for minimizing the costs toward a LCS in Japan. However, to take early actions, large investments will be needed at the initial stages. The investment requirements for the residential and commercial sector and transportation sector will be especially costly: The former reaching 2.5 trillion JPY annually from 2010 to 2025 and the latter reaching 2.5 trillion JPY annually from 2010 to 2015. There are four main advantages to early actions. (1) Technologies have learning-by-doing effects: The additional cost of reducing CO2 emissions will fall as the technologies spread. (2) If actions are delayed, learning-by-doing effects may fail to work sufficiently, resulting in higher total investment requirements for achieving a LCS. (3) No infrastructure can be built immediately; hence it would be difficult to switch suddenly to a LCS in the years just before 2050. (4) Future technological development has several uncertainties. If the development of one of the currently dominant technologies falls behind schedule, it will fail to spread as expected and CO2 emission targets will not be met. Early actions will open up new opportunities for the spread of alternative actions toward the LCS should a dominant technology fail in some way. [ABSTRACT FROM AUTHOR]