1. Introduction

AR5 (fifth assessment report) of IPCC (Intergovernmental Panel on Climate Change) has been published, and the report by WG1 (working group 1) states that “Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, and sea level has risen.”.
Research on the mechanism and impacts of climate change is under development, and ways of achieving the “stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system” in Article 2 of UNFCCC (the United Nations Framework Convention on Climate Change) are being pursued.
At the same time, research on effects of adaptation to climate change is also progressing.
In AR5 of IPCC, it is articulated that both mitigation and adaptation are indispensable to solve climate change issues.
However, they have been treated independently until very recently, and adaptation has hardly been focused on in Japan.
In summer 2015, a national adaptation policy by the Japanese government will be compiled, and support for effective and efficient climate change policies with a balance between mitigation and adaptation is expected for international negotiation on policies of climate change adaptation for developing states based on the Cancun agreements.

2. Research overview

In order to construct a sustainable society by an integrated approach involving mitigation and adaptation, how effectively and efficiently climate change issues can be solved with a delicate balance between mitigation and adaptation under limited economic and human resources will be assessed quantitatively, and it will be utilized to support climate change policy developments as risk management.
The following five themes have been set.

(1) Comprehensive and Strategic Assessment

A comprehensive assessment of relevant risks associated with climate change, among various global risks facing human beings, and a synthetic strategy to minimize the risks of climate change under limited economic and human resources are required. In this theme, research coordination, the promotion of collaboration, and progress management are carried out by the core team of this project. The results from all the themes under S-14 will be integrated, and it will be evaluated using various indices how effectively and efficiently climate change issues can be solved with a delicate balance between mitigation and adaptation (subtheme 1). Results from themes 2 and 3 will be synthesized in order to reveal the impacts of mitigation and adaptation to climate change by endpoint indicators such as human health and biodiversity, using the framework of LCA (life cycle assessment) (subtheme 2). A cost-benefit analysis method for mitigation and adaptation utilizing metrics, such as subjective wellbeing and DALY (disability-adjusted life years), will be developed in collaboration with subtheme 2, and will contribute to the synthesized assessment in subtheme 1 (subtheme 3).

As a whole, S-14 targets the global scale and assesses the balance between mitigation and adaptation to climate change by countries or regions. Among the available climate change scenarios of CMIP5 (coupled model intercomparison project phase 5), the RCP (representative concentration pathways) 8.5 and 2.6 scenarios will be mainly used. The research outcomes will be immediately published in international journals and, at the same time, summarized, translated, and utilized to support the development of climate change policies.

(2) Integrated Approach for Ecosystem-based Mitigation and Adaptation to Climate Change

Ecosystems have the functions of climate regulation and carbon storage, and at the same time reduce the risk of natural disaster caused by global warming, such as sea level rises, tidal waves, and forest fires. Therefore, the conservation of ecosystems can be effective as both adaptation and mitigation measures against climate change. On the other hand, here is a trade-off between the economic benefits of human activities for the current generation and the ecological risks facing future generations. These ecological risks are increased by the loss of biodiversity and ecosystem services. We will investigate (1) the prediction of the future changes in ecosystem service under scenarios by various policies, and (2) (co-benefit or trade-off) relationships between global mitigation and local adaptation measures. Our project will help to decide the best mix of mitigation-adaptation measures.

(3) Global Cost-benefit Analysis of Climate Change Adaptation

In this theme, the effects, costs and benefits of climate change adaptation at the global scale will be evaluated. The group will also focus on the synergistic effect between current disaster reduction activities and climate change adaptation, as well as strategic disaster reduction measures along with adaptation. The group will conduct research on global impact analysis due to climate change and cost-benefit analysis of feasible adaptations in the following four major sectors: (1) water-related disasters, (2) crop production, (3) health and hygiene, and (4) coastal disasters. In collaboration with theme 2, new insights obtained from these sectors will be used as required information in a computable general equilibrium model of mitigation and adaptation developed in theme 5. The group will also investigate current technical and economic issues in climate change adaptation at the global scale by referring to regional- scale analysis in theme 4.

(4) Case Study on Mitigation and Local Adaptation to Climate Change in an Asian Megacity, Jakarta

The most recent report of AR5 in IPCC suggested that the high risks due to global climate change are concentrated in urbanized areas. This theme conducts a case study on mitigation and local adaptation to climate change in an Asian megacity. The city of our focus is Jakarta, Indonesia, where rapid urban sprawl is expected to continue for the next several decades and multiple stresses involving water disaster, heat stress, and land subsidence exist. The expected contributions of this theme are (1) the establishment of a general methodology for the mixture of mitigation and adaptation for all developing countries and (2) the local validation of the global assessments targeted throughout S-14.
Subtheme 1 involves the projection of the urban climate under mitigation and local adaptation scenarios. Subtheme 2 involves doing the evaluation and cost-benefit analysis of policies to reduce the risk reduction of urban flooding based on mitigation and local adaptation. Subtheme 3 involves the urban health impact assessment and cost-benefit analysis of mitigation and local adaptation.

(5) Research on Development of an Integrated Assessment Model Incorporating Global-Scale Climate Change Mitigation and Adaptation

According to AR5 in IPCC, here is a need to implement the integrated and quantitative evaluation of climate change mitigation and adaptation policies. In this theme, we will estimate the costs of impact and adaptation policies consistent with global GHG emissions. Subtheme 1 will collect effects and cost benefit information for the case of implementing global climate change adaptation policies obtained from themes 2 and 3. We will then develop a computable general equilibrium model for the estimation of the following costs: (1) the reduction cost of global GHG, (2) the cost of impact damage, (3) the cost of adaptation policies. Subtheme 2 will carry out an investigation to establish theoretical and technical foundations for coupling global physical impact assessment models and general equilibrium models, which will be developed and obtained by themes 2 and 3. Subtheme 3 will develop an econometric model for discussing and supporting the validity of theories and parameters to be integrated in a computable general equilibrium model. Subtheme 4 will discuss the validity of scenario setting (assumed policy) for assessing policies of climate mitigation and adaptation by using a computable general equilibrium model from the perspective of international systems. Subtheme 5 will discuss the validity of scenario setting (assumed policy) for assessing policies of climate mitigation and adaptation by using a computable general equilibrium model from the perspective of governance and financing mechanisms.