Pricing greenhouse gas emissions involves making trade-offs between consumption today and unknown damages in the (distant) future. The optimal carbon dioxide (CO2) price, thus, is based on society’s willingness to substitute consumption across time and across uncertain states of nature. Standard constant relative risk aversion preference specifications conflate the two. Moreover, they are inconsistent with observed asset valuations, based on a large body of work in macroeconomics and finance. This literature has developed a richer set of preferences that are more consistent with asset price behavior and separate risk across time and across states of nature. In this paper, we explore the implications of these richer preference specifications for the optimal CO2 price. We develop the EZ-Climate model, a simple discrete-time optimization model in which the representative agent has an Epstein-Zin preference specification, and in which uncertainty about the effect of CO2 emissions on global temperature and on eventual damages is gradually resolved over time. We embed a number of features including potential tail risk, exogenous and endogenous technological change, and backstop technologies. The EZ-Climate model suggests a high optimal carbon price today that is expected to decline over time as uncertainty about the damages is resolved. It also points to the importance of backstop technologies and to very large deadweight costs of delay. We decompose the optimal carbon price into two components: expected discounted damages and the risk premium. JEL code: D81, G11, Q54.
Download publicationThis article presents an overview of the design and performance of seven major emissions trading programs that have been implemented over the past 30 years and identifies a number of important lessons for future applications of this important environmental policy instrument. A brief discussion of several other proposed or implemented emissions trading programs is also included.
The Paris Agreement has achieved one of two key necessary conditions for ultimate success – a broad base of participation among the countries of the world. But another key necessary condition has yet to be achieved – adequate collective ambition of the individual nationally determined contributions. How can the climate negotiators provide a structure that will include incentives to increase ambition over time? An important part of the answer can be international linkage of regional, national, and sub‐ national policies, that is, formal recognition of emission reductions undertaken in another jurisdiction for the purpose of meeting a Party’s own mitigation objectives. A central challenge is how to facilitate such linkage in the context of the very great heterogeneity that characterizes climate policies along five dimensions – type of policy instrument; level of government jurisdiction; status of that jurisdiction under the Paris Agreement; nature of the policy instrument’s target; and the nature along several dimensions of each Party’s Nationally Determined Contribution. We consider such heterogeneity among policies, and identify which linkages of various combinations of characteristics are feasible; of these, which are most promising; and what accounting mechanisms would make the operation of respective linkages consistent with the Paris Agreement.
Inadequate policy surveillance has undermined the effectiveness of multilateral climate agreements. To illustrate an alternative approach to transparency, I evaluate policy surveillance under the 2009 G-20 fossil fuel subsidies agreement. The Leaders of the Group of 20 nations tasked their energy and finance ministers to identify and phase-out fossil fuel subsidies. The G-20 leaders agreed to submit their subsidy reform strategies to peer review and to independent expert review conducted by international organizations. This process of developed and developing countries pledging to pursue the same policy objective, designing and publicizing implementation plans, and subjecting plans and performance to review by international organizations differs considerably from the historic approach under the UN Framework Convention on Climate Change. This paper draws lessons from the fossil fuel subsidies agreement for climate policy surveillance.