The authors break down the reasons for the United States to stay in the Paris Climate Agreement, arguing that the benefits far outweigh any potential costs. The Agreement gives the United States a seat at the table, and the ability to influence international policy on climate change, showing that the United States is open and willing to cooperate.

Robert Stavins argues for an economic approach to solving environmental problems and explains why "environmental economics" is not an oxymoron.

During the last ten years, a number of countries and sub-national jurisdictions have started greenhouse-gas emissions trading systems (ETSs), and a number of others are in planning and preparation. There is increasing interest in linking these systems, both directly and indirectly via connections to emissions-reduction-credit (ERC) systems, the largest of which is the Clean Development Mechanism (CDM) under the Kyoto Protocol. This research reviews the evidence of the past decade and finds a number of economic, political, and strategic factors influencing policy decisions about whether or not to link. Because the number of proposed and existing linkages is too small to permit a statistical analysis, we qualitatively identify the determinants of policy decisions involving linkage.

The Harvard Project co-sponsored a research workshop in May 2013 examining options for the UNFCCC's Durban-Platform process. This Issue Brief draws from and extends the discussion at the workshop.

The Durban Platform for Enhanced Action represents an important milestone in the history of climate negotiations.  The challenge is to find a way to include all key countries in a structure that brings about meaningful emission reduction on an appropriate timetable at acceptable cost, while recognizing the different circumstances of countries in a way that is more subtle, more sophisticated, and more effective than the dichotomous distinction of years past. This policy brief expands upon the authors' Science article, "Climate Negotiators Create an Opportunity for Scholars."

In this policy brief, Harvard Project Director Robert Stavins focuses on how subnational policies will interact with a federal climate policy. It turns out that some of the interactions will be problematic, others will be benign, and still others could be positive. He also examines the role that could be played by subnational policies in the absence of a meaningful federal policy, with the conclusion that—like it or not—we may find that Sacramento, California comes to take the place of Washington as the center of national climate policy. This case study might provide insight for COP 17 delegates in designing the next steps toward a flexible international agreement.

"...[B]ottom-up linkage of state and regional cap-and-trade systems could be an important part, or perhaps even the core, of future of U.S. climate policy, at least until there is meaningful action at the federal level. In the meantime, it is at least conceivable—and perhaps likely—that linkage of state-level cap-and-trade systems will become the (interim) de facto national climate policy architecture."

The Fifteenth Conference of the Parties (COP-15) of the United Nations Framework Convention on Climate Change (UNFCCC) reinforced doubts about whether the UNFCCC should continue to be the primary institutional venue for global climate change negotiations. This issue brief assesses some other institutions that might serve to supplement or partially replace the UNFCCC.

Our proposal for a post-2012 international global climate policy agreement contains three essential elements: meaningful involvement by key industrialized and developing nations; an emphasis on an extended time path of targets; and inclusion of market-based policy instruments. This architecture is consistent with fundamental aspects of the science, economics, and politics of global climate change.

An effective, but more flexible and politically palatable approach could be an international agreement on a "portfolio of domestic commitments." Under such an agreement, nations would agree to honor commitments to greenhouse gas emission reductions laid out in their own domestic laws and regulations. A portfolio of commitments may emerge from a global meeting such as the UNFCCC Conference of the Parties, or a smaller number of major economies could negotiate an agreement among themselves, and then invite other countries to join.