A Preview of COP31

As some of you may recall, since the summer of 2023, I have had the privilege of directing a university-wide effort – the Harvard Initiative on Reducing on Global Methane Emissions – with support from the Salata Institute for Climate and Sustainability.  Next week, at COP31 in Antalya, Türkiye, I will be making two presentations with my Harvard colleague, Professor Daniel Jacob, in regard to about two of the twenty-six individual research and outreach projects that are part of the Harvard methane initiative. 

One is the main focus of today’s essay, because it is very much at the heart of the UNFCCC process, including the Paris Agreement, and COP31 – using satellite-based estimates of national methane emissions to facilitate the process.  The other, which I will describe in a blog post subsequent to COP31, is work with my Harvard Kennedy School colleague, Joe Aldy, Harvard Business School Professor Forest Reinhardt, and Tracy Zhang, Harvard Public Policy PhD student, focused on estimating the marginal abatement costs of reducing methane emissions in the oil & gas (O&G) sector.

Before I turn to my major topic today, here is some information about the COP31 event focused on the second project above:  “Reducing Methane Emissions: Abatement Costs in the Oil and Gas Sector,” Wednesday, November 18, 1:00 – 2:30 PM TRT, Pavilion of the International Emissions Trading Association (IETA), Blue Zone, COP-31.  Panelists will include Daniel Jacob, myself, and others to be announced.  For background on this session, see this linked paper, released earlier in the abatement-cost project. 

Now I will turn to my major focus today.

Advancing Reporting of Satellite-Based Methane Emissions Estimates    to Support International Climate Policy Processes

In brief, the goal of this project with Daniel Jacob, Willow Fortunoff, and a host of talented pre-docs and post-docs from Daniel’s team, is to produce consistent national methane emissions estimates using a common methodology worldwide – the Integrated Methane Inversion (IMI) tool developed by Daniel’s team – as technical input to the Second Global Stocktake (GST2), and to encourage countries to use the IMI to strengthen their methane inventories and climate reporting under the Paris Agreement, including the Biennial Transparency Reports (BTRs) due December 2026.

If you want to learn more about the IMI tool and our outreach strategy, here’s video of a press conference we held earlier this week, and a good article about the underlying research is here.  If either of those are more than you want to watch or read, here’s a very brief description of the IMI tool, followed by an overview of our outreach strategy.

The IMI Tool

The Integrated Methane Inversion (IMI) is a free, open-source software tool that uses satellite observations to estimate how much methane a country emits at national, subnational, and sectoral levels. It helps countries check and improve the emissions figures they report to the United Nations. 

Here’s how it works.  The IMI starts with a country’s own national methane inventory, that is, its estimates to the UNfrom sources such as oil and gas operations, agriculture, and waste.  It then combines that starting estimate with daily, global observations of atmospheric methane from the TROPOMI satellite instrument (operating since 2018), plus data from other satellites that detect individual sources. Weather data help the tool account for how winds carry methane from its source to the places where satellites observe it.  Using this evidence, the IMI adjusts the country’s initial estimate. The results show estimated emissions across the country in areas roughly 12-25 kilometers across, along with a range that expresses the uncertainty in each estimate.  The IMI also shows national totals for emissions from human activity and estimates by sector.

What makes the IMI estimates different from other estimates?  Other satellite tools measure releases from individual sites, such as a leaking oil or gas facility. Those measurements help identify large emitters, but they do not provide a country’s total annual emissions. And, importantly, the IMI uses a common methodology for every country, allowing users to compare the results.

And here is what makes these estimates particularly reliable.  The IMI uses established scientific methods described in over 50 peer-reviewed publications. Its code is publicly available, its methods are documented, and it is designed for non-expert use. A 2025 study by James East (formerly a postdoc with Daniel Jacob and now a faculty member at MIT) and colleagues reports its estimates of methane emissions from human activity worldwide, country by country. Users can explore the results through an interactive web interface.

Using These National Estimates in Support of UNFCCC Processes

The Harvard team is helping governments, NGOs, and international institutions interpret and use the IMI national methane emission results.  Here is a brief overview of our communications and engagement strategy.

Let’s start with the Paris Climate Agreement, under which countries submit Nationally Determined Contributions (NDCs) every 5 years, and countries submit Biennial Transparency Reports (BTRs) every 2 years under the Enhanced Transparency Framework (ETF) of Article 13.  Whereas the NDCs are forward-looking, the BTRs are backward-looking, with the BTRs providing descriptions of progress towards NDCs, as well as self-assessment.  These are due December 31, 2026.

Another part of the Paris Agreement is the Global Stocktake, the second of which (GST2, 2024-2028) is being launched at COP31.  This assesses collective global progress toward meeting goals of the Paris Agreement, and the inputs include Party-reported ETF data, IPCC and other scientific assessments, and non-Party submissions.  The Information Collection and Preparation phase begins in late 2026, and our submission will be due in February 2027.

We build upon the IMI’s methodologically-consistent, high-resolution, satellite-informed estimates of national methane emissions, including sectoral detail, and then our strategic approach is to provide input to and support of both policy channels – the BTRs and GST2.  Our objectivefor December 2026 is that 10–20 countries use our IMI estimates as supporting evidence in their 2026 BTRs.  We are sharing country-level policy briefs with more than 40 countries, discussing each country’s specific concerns during a series of bilateral meetings.  The 40+ Fact Sheets can be downloaded here.  Here’s an example of one of the country fact sheets.

Finally, another element of our work in Antalya on this project is our Harvard Side Event at COP31 (“Quantifying and Communicating Methane Emissions for NDCs and the Global Methane Pledge,” Thursday, November 19, 2026 | 4:45 – 6:15 PM TRT, Side Event Room Yellow, Blue Zone, COP-31, with:  Dan Cusworth, Vice President for Science, Carbon Mapper; Daniel Jacob, Harvard University; Amanda McKee, Director for Knowledge and Learning, NDC Partnership; and myself). 

I hope very much to see some of you at COP31!

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Reflections on Bill Nordhaus

A call I received this morning from a (knowledgeable and very bright) economics reporter at the New York Times prompted me to reflect on the life and contributions of Bill Nordhaus, who sadly passed away on Friday.  I knew and interacted with Bill many times over the past 35 years, since my days as a relatively young assistant professor at Harvard.  I checked just now my database of past emails, as well as my records of letters and travels before the advent of email, and I was able to identify many occasions on which Bill and I had communicated over some thirty years, mainly but not exclusively about economic dimensions of climate change policy.

In the coming days, many economists and other academics will write about Bill Nordhaus’s important contributions to research on the economics of climate change, so I will focus instead in this brief essay on Bill’s contributions to public policy.  I can do this relatively quickly because a few years ago, my Harvard colleague, Joe Aldy, and I wrote an article (Climate Change Economics, 2020, Volume 11, Number 4) titled, “Rolling the Dice in the Corridors of Power:  William Nordhaus’s Impacts on Climate Change Policy.”  If you do not have access to the journal, I hope you will read the Harvard working paper version.

Nordhaus’s Contributions to Public Policy

Beyond the exceptionally important academic macroeconomic insights cited in his 2018 Nobel Prize, Nordhaus had significant influence on U.S. and international public policies to address climate change. Identifying those contributions is more challenging, partly because such influences are more subtle. That was the purpose of my 2020 article with Joe Aldy – to identify how Professor Nordhaus and his research had affected the path of climate change policy in the United States and around the world.  In the sincere hope that you will have time to read our article, linked above, I will do little more in this essay than provide a brief summary, indeed little more than a table of contents.

In reflecting broadly on how economists have impacts on the formulation of public policies, Aldy and I identified three distinct pathways.  

Direct Participation in the Policy World

First, there is direct participation in the policy world, such as via full-time government service or part-time service on a government committee. In the case of Bill Nordhaus, three engagements fell into this first pathway: (1) Member, Council of Economic Advisers, 1977-1979; (2) Chairman, National Academy of Sciences (NAS) Panel on Integrated Environmental and Economic Accounting, 1996-1999; and (3) Chairman, NAS Committee on the Effects of Provisions in the Internal Revenue Code on Greenhouse Gas Emissions, 2011-2013.

Directly Influencing the Formulation of Public Policies

The second of the three pathways is that of directly influencing the formulation of public policies, a pathway that is considerably less frequent than commonly assumed. One very significant example of this in the case of Nordhaus was the explicit use of Bill’s Dynamic Integrated Climate-Economy (DICE) model by the Obama and Biden administrations in their development of quantitative estimates of the “social cost of carbon” (Interagency Working Group on Social Cost of Carbon, United States Government 2010, 2013, 2015, 2016).

Indirectly Informing Public Policy

The third and final pathway is by far the most common:  indirectly informing public policy. This category is the most challenging to assess, because the picture becomes clouded by the first half of the well-known proverb that “success has many fathers, but failure is an orphan.” Subject to that caveat, we examined six distinct ways in which Nordhaus’s economic research indirectly informed climate change policy:  (1) examining the balance of economic growth and climate protection; (2) applications and extensions of the DICE model; (3) estimating the dynamically efficient time path of global greenhouse gas (GHG) emissions; (4) examining cost-effective methods of GHG emissions mitigation; (5) alternative approaches to international cooperation; and (6) policy-relevant intellectual debates (including those between Bill Nordhaus and Marty Weitzman).

Putting It All Together

The seminal contributions of Bill Nordhaus to fundamental scholarship on the long-run macroeconomics of global climate change are abundantly clear.  But, as Joe Aldy and I found, it is more challenging to identify the impacts of Nordhaus and his research on public policy (in the climate domain). In the short term, at least, more easily digestible symbols – for example, targets of 2oC or 1.5 oC maximum temperature change by 2100 or net zero emissions in 2050 – may matter more for public policy than even the best, most rigorous scholarly research. This is hardly unique.  The limited influence of economic analysis on real world policy making (apart from macroeconomic policy) has long been noted, although within the realm of environmental policy, such influence seems to have increased over recent decades.

In general, personal involvement in the policy world – in Nordhaus’s case decades ago at the Council of Economic Advisers and the National Academy of Sciences – typically provides the most transparent evidentiary trail. Although even here, it is clouded by the passage of time. Some of Nordhaus’s most important contributions to climate change policy from that period – such as his support at President Carter’s CEA of the use of benefit-cost analysis to assess proposed government regulations – came to fruition only years later, beginning in the Reagan administration, with the first formal requirements for Regulatory Impact Analysis (RIA).

The second pathway above, which many economists seem to think is important and even quite common, is that of directly influencing the formulation of public policies. When and if this occurs, the evidence ought to be abundant and compelling. So it is with the use of Nordhaus’s DICE model as one of three IAMs employed by the Obama and Biden administrations to estimate empirically the Social Cost of Carbon. That the SCC has itself been used repeatedly for benefit calculations in RIAs demonstrates this direct connection of Nordhaus’s research and the formulation of public policies. But it should not be surprising that we could identify only one example of the second pathway, because this pathway is a rare one in the work of any environmental economist.

The third pathway – indirectly informing public policy – is the most important one through which Nordhaus’s work has had impacts on public policy. Reflecting on the work of other scholars suggests that this is broadly the case for academic microeconomic research influencing public policy, at least in the environmental realm. But here the evidence can be difficult to discern, partly because “success has many fathers.”

William Nordhaus is surely the most important economist to have worked on climate change and climate change policy.  If my assessment with Joe Aldy was correct that Nordhaus’s influence in the policy world was subtle and often indirect, then perhaps we should all be left with a sense of enhanced modesty regarding our own contributions to public policy.  And that includes me.

I will miss seeing Bill, talking with him, and hearing his voice.

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Reflecting on a Decade of Covering Climate Policy for the New York Times

I have had the great pleasure of engaging in conversations over the past 5 years with outstanding individuals from the worlds of academia, private industry, NGOs, government, and journalism in my monthly podcast series, “Environmental Insights: Discussions on Policy and Practice from the Harvard Environmental Economics Program.”  My most recent guest was certainly no exception, because I was joined by Lisa Friedman, a leading climate reporter at the New York Times, and previously for eight years at Climatewire/E&E News, where she was international reporter, deputy editor, and eventually Editor-in Chief.

Since moving to the Times in 2017, she has become widely regarded as one of the leading journalists in the world covering climate policy, and unlike most climate reporters who focus primarily on climate science, her reporting has emphasized government decision-making, regulation, international negotiations, energy economics, and the political economy of climate and energy policy.

She is about to undertake a major career transition, moving from the Climate Desk to the Business Desk as the Times’s London-based Energy Correspondent covering Europe and the Middle East.  So, I thought this was an excellent time to reflect with Lisa on her near-decade covering climate change and climate change policy for the New York Times, and to think about her path ahead.  Please listen to our full conversation here.

At the outset, Lisa emphasizes her excitement about this transition covering an increasingly important set of issues with ripple effects across multiple domains.

“Covering climate change is, of course, about covering energy choices, but it is also about politics and policy. It is also about food security. It is also a story about national security. It’s a story about everything from migration to intellectual property decisions,” she remarks.

She goes on to argue that dramatically shifting U.S. climate policies in recent years have cast the nation as an unreliable climate partner on the world stage, something that is becoming even more pronounced since President Trump’s re-election in 2024.

“We have seen efforts to impose regulations, EPA regulations on power plants, on automobiles, that were put in place under Democratic administrations, repealed under Republican administrations, [and then] put back in place and strengthened under the next Democratic administration,” she says. “And now with this second Trump administration, what we’re seeing is a real effort to not just wind back regulations but try to make sure that they are not ever able to be reinstated. That’s a huge shift.”

Friedman recognizes that her new beat will be a significant and very attractive challenge as she expands her purview to a European perspective.

“I don’t see myself as leaving the climate story. I am learning another side of the coin,” she says. “I think that as we think about things like the global energy transition, it’s really important for climate reporters to understand the oil and gas industry a lot better and understand where this industry is going to go in the future. That’s one of my big questions. The speed or slowness of the transition right now in this moment of how countries are reacting to the energy shocks brought about by the closing of the Strait of Hormuz. These are all just incredible stories that I’m excited to start telling.”

Lisa acknowledges that while there is support for the clean energy transition in the European Union (EU), there are also concerns about energy security and affordability at a time when citizens in many countries are feeling economic pressures.

“I spoke with Dan Jørgensen, Commissioner for Energy in the EU, and he pointed out that the block spends about 370 billion euros, that’s about 423 billion dollars, in imported energy every year. His argument, [as well as] the argument of many people who believe like him that electrification is important to Europe’s future, say, ‘Look, that is leaving Europe vulnerable to global market price swings. And by the way, we also don’t want to be vulnerable to a country that may put pressure on us in other ways for imported fuel.’”

“At the same time, you have many others in Europe who are… using the phrase ‘energy realism’ now, particularly in Greece and Cyprus, who are saying that the future of Europe is about diversification,” she states. “These are battles that are going to play out for many years now.”

Despite the disappointment many people have with the U.S. withdrawing from the Paris Agreement and with plans to withdraw from the United Nations Framework Convention on Climate Change (UNFCCC), Friedman says the issue of climate change isn’t going away.

“Yale University just came out with a poll that showed… no matter what the administration says about climate change, two thirds of Americans say they are worried about climate change. And figuring out how to cover climate change in this moment is a struggle for all of us,” she remarks. “But let’s not pretend the issue has gone away just because a particular administration doesn’t prioritize it or actively works against addressing it.”

For this and much, much more, I encourage you to listen to this 76th episode of the Environmental Insights series, with future episodes scheduled to drop each month.  You can find a transcript of our conversation at the website of the Harvard Environmental Economics Program.  Previous episodes have featured conversations with:

  • Gina McCarthy, former Administrator of the U.S. Environmental Protection Agency
  • Nick Stern of the London School of Economics discussing his career, British politics, and efforts to combat climate change
  • Andrei Marcu, founder and executive director of the European Roundtable on Climate Change and Sustainable Transition
  • Paul Watkinson, Chair of the Subsidiary Body for Scientific and Technological Advice (SBSTA) within the United Nations Framework Convention on Climate Change
  • Jos Delbeke, professor at the European University Institute in Florence and at the KU Leuven in Belgium, and formerly Director-General of the European Commission’s DG Climate Action
  • David Keith, professor at Harvard and a leading authority on geoengineering
  • Joe Aldy, professor of the practice of public policy at Harvard Kennedy School, with considerable experience working on climate change policy issues in the U.S. government
  • Scott Barrett,  professor of natural resource economics at Columbia University, and an authority on infectious disease policy
  • Rebecca Henderson, John and Natty McArthur University Professor at Harvard University, and founding co-director of the Business and Environment Initiative at Harvard Business School.
  • Sue Biniaz, who was the lead climate lawyer and a lead climate negotiator for the United States from 1989 until early 2017.
  • Richard Schmalensee, the Howard W. Johnson Professor of Management, and Professor of Economics Emeritus at the Massachusetts Institute of Technology.
  • Kelley Kizier, Associate Vice President for International Climate at the Environmental Defense Fund.
  • David Hone, Chief Climate Change Adviser, Shell International.
  • Vicky Bailey, 30 years of experience in corporate and government positions in the energy sector. 
  • David Victor, professor of international relations at the University of California, San Diego.
  • Lisa Friedman, reporter on the climate desk at the The New York Times.
  • Coral Davenport, who covers energy and environmental policy for The New York Times from Washington.
  • Spencer Dale, BP Group Chief Economist.
  • Richard Revesz, professor at the NYU School of Law.
  • Daniel Esty, Hillhouse Professor of Environment and Law at Yale University. 
  • William Hogan, Raymond Plank Research Professor of Global Energy Policy at Harvard.
  • Jody Freeman, Archibald Cox Professor of Law at Harvard Law School.
  • John Graham, Dean Emeritus, Paul O’Neill School of Public and Environmental Affairs, Indiana University.
  • Gernot Wagner, Clinical Associate Professor at New York University.
  • John Holdren, Research Professor, Harvard Kennedy School.
  • Larry Goulder, Shuzo Nishihara Professor of Environmental and Resource Economics, Stanford University.
  • Suzi Kerr, Chief Economist, Environmental Defense Fund.
  • Sheila Olmstead, Professor of Public Affairs, LBJ School of Public Affairs, University of Texas, Austin.
  • Robert Pindyck, Bank of Tokyo-Mitsubishi Professor of Economics and Finance, MIT Sloan School of Management.
  • Gilbert Metcalf, Professor of Economics, Tufts University.
  • Navroz Dubash, Professor, Centre for Policy Research, New Delhi.
  • Paul Joskow, Elizabeth and James Killian Professor of Economics emeritus, MIT.
  • Maureen Cropper, Distinguished University Professor, University of Maryland.
  • Orley Ashenfelter, the Joseph Douglas Green 1895 Professor of Economics, Princeton University.
  • Jonathan Wiener, the William and Thomas Perkins Professor of Law, Duke Law School.
  • Lori Bennear, the Juli Plant Grainger Associate Professor of Energy Economics and Policy, Nicholas School of the Environment, Duke University.
  • Daniel Yergin, founder of Cambridge Energy Research Associates, and now Vice Chair of S&P Global.
  • Jeffrey Holmstead, who leads the Environmental Strategies Group at Bracewell in Washington, DC.
  • Daniel Jacob, Vasco McCoy Family Professor of Atmospheric Chemistry & Environmental Engineering at Harvard.
  • Michael Greenstone, Milton Friedman Distinguished Service Professor of Economics, University of Chicago.
  • Billy Pizer, Vice President for Research & Policy Engagement, Resources for the Future. 
  • Daniel Bodansky, Regents’ Professor, Sandra Day O’Connor College of Law, Arizona State University.
  • Catherine Wolfram, Cora Jane Flood Professor of Business Administration, Haas School of Business, University of California, Berkeley, currently on leave at the Harvard Kennedy School.
  • James Stock, Harold Hitchings Burbank Professor of Political Economy, Harvard University.
  • Mary Nichols, long-time leader in California, U.S., and international climate change policy.
  • Geoffrey Heal, Donald Waite III Professor of Social Enterprise, Columbia Business School.
  • Kathleen Segerson, Board of Trustees Distinguished Professor of Economics, University of Connecticut.
  • Meredith Fowlie, Professor of Agricultural and Resource Economics, U.C. Berkeley. 
  • Karen Palmer, Senior Fellow, Resources for the Future.
  • Severin Borenstein, Professor of the Graduate School, Haas School of Business, University of California, Berkeley.
  • Michael Toffel, Senator John Heinz Professor of Environmental Management and Professor of Business Administration, Harvard Business School.
  • Emma Rothschild, Jeremy and Jane Knowles Professor of History, Harvard University.
  • Nathaniel Keohane, President, C2ES.
  • Amy Harder, Executive Editor, Cypher News.
  • Richard Zeckhauser, Frank Ramsey Professor of Political Economy, Harvard Kennedy School.
  • Kimberly (Kim) Clausing, School of Law, University of California at Los Angeles
  • Hunt Allcott, Professor of Global Environmental Policy, Stanford Doerr School of Sustainability.
  • Meghan O’Sullivan, Jeane Kirkpatrick Professor of the Practice of International Affairs at Harvard Kennedy School.
  • Robert Lawrence, Albert Williams Professor of International Trade and Investment, Harvard Kennedy School.
  • Charles Taylor, Assistant Professor of Public Policy, Harvard Kennedy School.
  • Wolfram Schlenker, Ray Goldberg Professor of the Global Food System, Harvard Kennedy School.
  • Karen Fisher-Vanden, Professor of Environmental & Resource Economics, Pennsylvania State University
  • Max Bearak, climate and energy reporter, New York Times
  • Vijay Vaitheeswaran, global energy and climate innovation editor, The Economist
  • Joseph Aldy, Teresa & John Heinz Professor of the Practice of Environmental Policy, Harvard Kennedy School
  • Nicholas Burns, Roy and Barbara Goodman Family Professor of the Practice of Diplomacy and International Relations, Harvard Kennedy School
  • Elaine Buckberg, Senior Fellow, Salata Institute for Climate and Sustainability, Harvard University
  • Anna Russo, Junior Fellow, Harvard University
  • John Podesta, Advisor to Presidents Clinton, Obama, and Biden
  • Catherine Wolfram, William Barton Rogers Professor of Energy Economics, MIT Sloan School of Management
  • Jody Freeman, Archibald Cox Professor of Law at Harvard Law School.
  • Matthew Kahn, Provost Professor of Economics, University of Southern California
  • Kenneth Gillingham, Professor Economics, Yale School of the Environment

“Environmental Insights” is hosted on SoundCloud, and is also available on iTunes, Pocket Casts, Spotify, and Stitcher.

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