On September 25, 2015, Presidents Xi Jinping of China and Barack Obama of the United States reaffirmed their "shared conviction that climate change is one of the greatest threats facing humanity and that their two countries have a critical role to play in addressing it." The Joint Presidential Statement on Climate Change built upon that of November 12, 2014 and contains pledges to cooperate: 1) To produce an ambitious multilateral agreement at the Twenty-First Conference of the Parties to the United Nations Framework Convention on Climate Change (UNFCCC) in Paris in December 2015; 2) To advance respective domestic actions (detailed in the announcement) to reduce greenhouse-gas emissions; and 3) To enhance bilateral and multilateral cooperation through forums other than the UNFCCC.

The collaborators conducted a research workshop in February 2015, hosted by the Mercator Institute in Berlin, on approaches to improving the process by which research on climate change is assessed—with a focus on the social sciences (economics, political science, policy studies). The Science article captures some of the more important conclusions of this workshop.

"The Intergovernmental Panel on Climate Change (IPCC) has proven its value as an institution for large-scale scientific collaboration to synthesize and assess large volumes of climate research for use by policy-makers, as well as for establishing credibility of findings among diverse national governments. But the IPCC has received considerable criticism of both its substance and process."

The Harvard Project on Climate Agreements co-organized a workshop on China-U.S. collaboration on climate-change policy on June 25–26, 2015 in Beijing. The workshop was hosted and co-organized by the National Center for Climate Change Strategy and International Cooperation.

On August 3, 2015, President Barack Obama and U.S. Environmental Protection Agency Administrator Gina McCarthy released the final version of the Clean Power Plan (CPP). The CPP's goal is to reduce emissions of CO2 in the United States by 32 percent in 2030, relative to 2005 emissions. See earlier analysis of the CPP by Harvard faculty members and other Harvard-Project affiliates here and here and reaction to the final version by faculty affiliated with the Harvard Law School Environmental Law Program.

Experts from universities, think tanks, the World Bank, and private companies met at the Harvard Kennedy School on May 7 and 8, 2015 to discuss how flexible approaches to exchanging mitigation commitments might be incorporated into the new climate agreement to be concluded in Paris later in 2015. The workshop, "Comparison and Linkage of Mitigation Efforts in a New Paris Regime," was co-sponsored by the International Emissions Trading Association (IETA), Harvard Project on Climate Agreements, and World Bank Group's Networked Carbon Markets Initiative.

On February 18–20, 2015, twenty-four experts gathered in Berlin to explore approaches to improving the process by which research on climate change is assessed—with a focus on the social sciences (economics, political science, policy studies). Participants discussed potential reforms in the assessments of the Intergovernmental Panel on Climate Change (IPCC) and also the development of assessment processes complementary to the IPCC.

James Stock, a Faculty Fellow of the Harvard Environmental Economics Program—the Harvard Project's parent program—organized a roundtable discussion that took place on January 4, 2015, at the annual meeting of the Allied Social Science Association, held this year in Boston, entitled "The Economics of the EPA's Proposed Regulation of CO2 Emissions from Power Plants." Professor Stock was a member of President Obama's Council of Economic Advisors in 2013–2014, where he worked on the development of this important regulatory proposal. Harvard Environmental Economics Program (HEEP) and Harvard Project Director Robert Stavins participated in the roundtable panel.

Improving end-use energy efficiency—that is, the energy-efficiency of individuals, households, and firms as they consume energy—is often cited as an important element in efforts to reduce greenhouse-gas (GHG) emissions. Arguments for improving energy efficiency usually rely on the idea that energy-efficient technologies will save end users money over time and thereby provide low-cost or no-cost options for reducing GHG emissions. However, some research suggests that energy-efficient technologies appear not to be adopted by consumers and businesses to the degree that would seem justified, even on a purely financial basis.

The Harvard Project co-sponsored a symposium in New York on Sept. 22, 2014 exploring the role of linkage in a new international climate agreement.