This paper provides an overview of the standard theory of discounting in cost-benefit analysis. With an application to long-term environmental problems in mind, we begin with the classic issue of discounting and intergenerational equity, which dates back to the seminal work of Frank Ramsey in the 1920s. Then, by reviewing recent developments in the theory of declining discounting rates (DDRs), we show how relatively low and declining discount rates can be justified in the presence of uncertainty. Also, we briefly discuss the practical implications of discounting in the context of climate change.

There are a number of possible structures of cooperation or agreement that avoid a tragedy of global commons. The structure of the Paris Agreement is in common with that of the Kyoto Protocol in the aspect that each country has an emissions target, part of which can be traded among countries. However, some economists have been proposing that the target should be carbon price. That is the target of marginal cost of reduction. Their reasoning has recently become diversified. In this paper, the Paris Agreement is evaluated from the diversified viewpoint of quantity vs. price, based on the Paris Agreement itself and its negotiation process. The appropriateness of the price target proposal is also investigated. Although the price target proposal is persuasive, further investigation is found to be necessary.

Actions and policies for achieving sustainable consumption and production (SCP) systems are applied at various levels, including UNEP and other international organizations, and national government. Based on the 2015 SEEPS annual meeting discussions on SCP, we discuss the current status of those actions and the role of various actors such as consumers and firms.