Martin Weitzman’s Contributions to Environmental Economics

Many of the world’s most eminent economists and climate scientists gathered on October 11th, 2018, at Harvard Kennedy School to celebrate and honor the career of Martin L. Weitzman, professor of economics at Harvard University, who is “retiring” following four decades of research and writing which have illuminated thought and policy across a broad range of important realms. During his “retirement,” Marty will serve as a Research Professor in Harvard’s Department of Economics.

The October 11th event, “Frontiers in Environmental Economics and Policy: A Symposium in Honor of Martin L. Weitzman,” which drew about 250 people, was organized and hosted by the Harvard Environmental Economics Program (HEEP), with additional support from the Harvard University Center for the Environment and the Mossavar-Rahmani Center for Business and Government at the Kennedy School.

Having learned so much from Marty Weitzman, including during the 26 years that he and I have been co-hosting the Harvard Seminar in Environmental Economics and Policy, I was delighted to moderate the symposium.  From the earliest days of planning the event until the day of the symposium, my team – Rob Stowe, HEEP Executive Director, Jason Chapman, HEEP Program Manager, and Casey Billings, HEEP Program Coordinator – and I were inspired by the breathtaking contributions Marty has made to the once-emerging and now mature global discipline of environmental economics.

In my blog essay today, I want to provide for those who could not attend a sense of what it was like to be there, and remind those who did attend what transpired.

Introducing Professor William Nordhaus

I began the symposium by introducing our keynote speaker, William D. Nordhaus, who just a few days earlier had been announced as a recipient of this year’s Nobel Prize in Economics for his work on modeling the economics of climate change and related public policies.

The cliche that “our speaker needs no introduction” certainly applied here, and so I was very brief, noting first that for nearly four decades, Bill Nordhaus has written about the economics of the environment.  Building on his background as a macro-economist concerned about economic growth, Bill began to give particular attention to the role of energy generation and use in the 1970s, not long after beginning his academic career.  What is truly remarkable is that it was in the early 1980s that he began working on the economics of global climate change, long before most other economists were even aware of the problem, let alone analyzed it.

Bill has been on the faculty at Yale University since 1967, where he is the Sterling Professor of Economics, and Professor in Yale’s School of Forestry and Environmental Studies.  He is a member of the National Academy of Sciences, a Fellow of the American Academy of Arts and Sciences, a Distinguished Fellow of the American Economic Association, and a Research Associate of the National Bureau of Economic Research.  In addition to his many scholarly achievements, he served as a Member of the President’s Council of Economic Advisers in the Carter administration.

What is particularly striking about Bill Nordhaus’s contributions is that — as long as I can remember — he has made his path-breaking DICE model of global climate change economics accessible to and usable by other researchers around the world.

Keynote Address by Bill Nordhaus

Bill launched his presentation, “The Intellectual Footprint of Martin Weitzman in Environmental Economics,” by stating that Marty “has changed the way we think about economics and the environment.”  He then went on to itemize Weitzman’s impressive body of work, including his series of studies on the share economy; his research on the Soviet Union and central planning; his seminal 1974 paper, “Prices vs. Quantities,” which provided fresh insight on how regulatory policy can best be leveraged to maximize public good; and his work on so-called “fat tails” and the “dismal theorem,” which questioned the value of a standard benefit-cost analysis when conditions could result in catastrophic events, even if the probability of such events is very low.

But Nordhaus devoted much of his talk to highlighting Weitzman’s extraordinary contributions to the field of environmental economics, in particular, the economics of climate change and climate change policy. It was Weitzman’s “revolutionary” series of papers on the ideal measures of national income, Nordhaus stated, that focused early attention on the need to take the harmful impacts of pollution into account when tabulating the gross domestic product (GDP), a concept referred to as “Green GDP.”

“Our output measures do not include pollution,” said Nordhaus. “They include goods like cars and services like concerts and education, but they do not include CO2 that is pumped into the atmosphere.”  He explained that pollution abatement measures are often blamed for causing a drag on the economy, but aren’t credited for the health and welfare benefits they create.

“If our incomes stay the same but we are healthier, and live a year longer or ten years longer, that will not show up in the way we measure things,” Nordhaus remarked. “But we can apply these Weitzman techniques to value improvements in health and happiness.”

“Those who claim that environmental regulations hurt growth are completely wrong, because they are using the wrong yardstick,” Bill continued. “Pollution should be in our measures of national output, but with a negative sign, and if we use green national output as our standard, then environmental and safety regulations have increased true economic growth substantially in recent years…For this important insight we applaud Martin Weitzman, a radically innovative spirit in economics.”

A Panel of Leading Environmental Economists

Following the keynote address by Nordhaus, I welcomed to the stage fellow economists Maureen Cropper, Lawrence Goulder, Michael Greenstone, Charles Kolstad, Richard Newell, Robert Pindyck, and James Stock for a lively panel discussion.  Each of these economists have themselves made important contributions to scholarship and policy in the environmental realm.

To each panelist, I posed a question about a different aspect of Marty Weitzman’s key contributions – ranging from climate change policy to biodiversity and fisheries management.

First, Richard Newell, the President and CEO of Resources for the Future (RFF) and a former student of Weitzman when he studied for his Ph.D. in Public Policy at the Harvard Kennedy School, described Weitzman’s seminal paper, “Prices vs. Quantities”, as a “gift that keeps on giving” for economists and policy makers invested in improving regulatory policy.

Next, Charlie Kolstad, a Senior Fellow at the Stanford Institute for Economic Policy Research, focused on Marty Weitzman’s research on biodiversity, and cited it for its “significance and importance.”

Third up was Larry Goulder, the Shuzo Nishihara Professor of Environmental and Resource Economics at Stanford University and a former colleague of Weitzman in the Harvard Department of Economics.  Larry described the importance of Marty’s work on long-term discounting, and commended his 1998 paper on declining discount rate profiles, noting that it has affected public policies in Denmark, France, and Norway, as well as public discussion in the Netherlands, Sweden, and elsewhere. Larry noted that “it’s very important, because it affects decisions as to how much we should invest in infrastructure, in mitigation, and in other realms.”

Fourth on the panel was Bob Pindyck, the Bank of Tokyo-Mitsubishi Professor of Economics and Finance at the Sloan School of Management at MIT, who is very familiar with Marty Weitzman’s work on fat-tailed distributions, and has contributed to that literature himself.  Bob cited Weitzman’s prescient 2007 paper “Subjective Expectations and Asset-Return Puzzles” for its significant influence upon the later modeling of the economics of catastrophic climate change.

Next was Jim Stock, the Harold Hitchings Burbank Professor of Political Economy at Harvard University.  I asked Jim to comment on the effect of Marty’s work on the policy world.  Jim started by crediting Weitzman for the “tremendous influence” his ideas have had upon the formation of public policy in the United States and around the world, citing the nine-state Regional Greenhouse Gas Initiative (RGGI), and the Clean Power Plan introduced by President Obama in 2015.

Sixth on the panel was Maureen Cropper, Distinguished University Professor and Chair of the Department of Economics at the University of Maryland.  Maureen had kindly agreed to talk about Marty Weitzman’s research and outreach in the realm of fisheries management.  Maureen explained that his modeling work in Iceland and elsewhere had affected thinking and discussion around the world regarding the use of taxes and quotas to regulate fishing industries. “This is another example of the use of a simple model and treatment of uncertainly that really did start a conversation among fisheries economists when it came out,” she said.

Finally Michael Greenstone, the Milton Friedman Professor in Economics at the University of Chicago, agreed to reflect on how Weitzman’s theoretical insights were fundamental as the foundation for sound empirical analysis.  Greenstone noted that Marty’s work “takes something you are kind of confused about, and then after you read it, you can’t understand how in the world you were confused beforehand. It just clarifies things in a way that is really beautiful.”

A Book of Testimonials

Many of those who attended the symposium — and many who were not able to join us — wanted to tell Marty directly how they feel about him and his work.  And so we assembled and presented to Marty a book in which we had compiled 60 testimonial letters, including from some of his admirers who could not be with us at the symposium, such as:  Orley Ashenfelter, Greg Mankiw, Kerry Smith, Bob Solow, Nick Stern, Cass Sunstein, and others.  As I presented Marty with the book of letters, I took a moment to read aloud from just one of the letters from another person who could not be with us:

When I was an undergraduate in the economics department at MIT, you were a bright and rising young star.  Later, as a faculty member, I routinely assigned your papers to my environmental economics students.  Your scholarship and your leadership enriched their experiences — and mine — tremendously.

I will never forget when you announced that you were moving on to Harvard — what a blow! —but the universe has seen fit to bring us together once again.  It is an honor to acknowledge your extraordinary contributions to the field, and to thank you for shining a light for all of us.

                                                      All the best,

                                                             Larry

                                                      Lawrence Bacow, President, Harvard University

More Memories

The book did not end with the testimonial letters.  On a personal note, it has been 26 years since Marty Weitzman and I launched the Harvard Seminar in Environmental Economics and Policy.  Over those 52 semesters, we have hosted a total of 398 seminars!  In the very first semester — the fall of 1992 — the seminar presenters included, among others, in alphabetical order: Bill Nordhaus, Kerry Smith, Bob Solow, Rob Stavins, Kip Viscusi, and Marty Weitzman.

In virtually every one of these 400 seminars, everyone in the seminar room – including me — learned not only from each seminar’s presenter, but from Marty’s concise and relevant questions which would inevitably go directly to the heart of the matter.  So, I was pleased to include in the book copies of all 52 seminar schedules, beginning with the fall of 1992 and culminating with the fall of 2018.  I will not say “concluding” with the fall of 2018, because I trust that my collaboration with Marty, which I have valued highly, will continue.

Marty Weitzman has been a treasure for Harvard and for the global scholarly community.  All of us are confident that his contributions will continue to be forthcoming.

Marty Weitzman Responds

Following the Symposium, Weitzman took several minutes to reflect on his remarkable career, recognizing that while he has pursued projects across multiple disciplines, his research would often hit dead ends.

“I’m drawn to things that are conceptually unclear, where it’s not clear how you want to make your way through this maze,” he said. “It’s difficult to describe a creative process, but I get some sort of an inspiration…Most of the time it’s a waste of time because I can’t formalize it, so I try and try and just nothing comes of it. But occasionally it clicks and since it’s typically in an area that’s been understudied, that’s why it’s so dispersed across different fields.”

Weitzman spoke proudly of his work in environmental economics, stating that he “took a decisive step in that direction a few decades ago…getting into the forefront rather than…following everything that went on.” Yet he admitted that he is not very optimistic about the current pace of efforts to combat the harmful mid- and long-term impacts of global climate change.

“It’s not merely sufficient to cut back on carbon emissions or to stabilize carbon emissions. We’ve more or less done that in the last few years, although it could go either way,” he said. “The stuff that does the damage is the stock of carbon dioxide. To get the stock of carbon dioxide to go down, it has almost nothing to do with stabilizing the flow. You have to get the flow down to net zero. That’s what’s so difficult. And the public does not realize that. Victory on the flow front doesn’t translate into victory on the stock front, and that’s what counts.”

As is typical of his style, Marty did not reveal his future plans, saying only that they remain to be determined.  But certainly all those in attendance at the symposium hope that he will continue contributing to the academic and policy discussions surrounding climate change and other critically important environmental economic issues.

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Inviting you to a Celebration of the Contributions of Martin Weitzman to Environmental Economics

Even the shortest of short lists of scholars who have made the greatest contributions to environmental economics would include my colleague, Professor Martin L. Weitzman of the Department of Economics at Harvard University.  His seminal contributions are legendary, including within the literatures of efficient policy instrument choice under uncertainty, optimal economic growth, biodiversity, long-term discounting, and the economics of catastrophic climate change.

In a future blog post, I will offer a fuller essay on Martin Weitzman’s great contributions to environmental economics, but today I wish to alert the readers of my blog that we – the Harvard Environmental Economics Program – are holding an important event at Harvard on the occasion of Professor Weitzman’s “retirement” (as if Marty will ever really retire!).  The event, “Frontiers in Environmental Economics and Policy:  A Symposium in Honor of Martin L. Weitzman,” will take place on Thursday, October 11th, 2018, from 3:00 to 5:30 pm (with a reception to follow), at the Harvard Kennedy School’s Nye Conference Room on the 5th floor of the Taubman Building.

The Keynote Speaker will be William D. Nordhaus, Sterling Professor of Economics at Yale University, who will speak on “The Intellectual Footprint of Martin Weitzman in Environmental Economics.”

Following Bill’s keynote address, I will have the privilege of moderating a panel of scholars, who themselves have made important contributions to environmental economics, and who will address various elements of Marty Weitzman’s scholarly work.  The panel will consist of the following distinguished participants (in alphabetical order):

I hope you will be able to join us for this very special afternoon.  The symposium is public, but if you would like to attend, it is necessary that you RSVP at https://heep.hks.harvard.edu/weitzman, or by contacting Casey Billings via email or by phone at 617-384-8415.

Finally, I’m pleased to say that the Harvard Environmental Economics Program will host the day’s events with support from the Harvard University Center for the Environment and the Mossavar-Rahmani Center for Business and Government at Harvard Kennedy School.

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Will the Paris Agreement Help or Hinder Cooperation among Nations?

I just returned from Florence, Italy, where I participated in the Second Carbon Market Workshop, organized by the European Commission, and hosted by the European University Institute.  This workshop, which brought together government representatives from around the world (with a sprinkling of academics and NGO representatives to add some spice to the discussion), was convened to examine how regional, national, and sub-national jurisdictions can cooperate in ways that could increase the effectiveness and/or reduce the costs of their respective climate change policies.  One of my tasks at the workshop was to make a brief dinner speech.  Jos Delbeke, the long-time,  legendary Director-General of Climate Action for the Commission, asked me to talk about how the Paris Agreement might help or hinder practical climate policy cooperation around the world.  I drew extensively upon my research with Michael Mehling and Gilbert Metcalf.  Here is the gist of what I said in my dinner speech.

Some Paris Agreement Fundamentals

The hybrid design of the Paris Agreement was key to its successful enactment in 2015 and its coming into force in November, 2016.  The hybrid design to which I refer is the combination of top-down (centralized) and bottom-up (decentralized) elements.  The top-down elements include, for example, the requirement that countries state their national contributions every five years, a schedule which is binding under international law for those jurisdictions that have ratified the Agreement.  The key bottom-up element is the set of individual Nationally Determined Contributions (or NDCs) themselves, which are not part of the Paris Agreement itself, but rather are listed in a separate Registry.  These are not binding under international law, but rather are left to the domestic authority of the respective countries.

This dual structure led to the achievement of one of two necessary conditions for ultimate success of the Paris Agreement, namely adequate scope of participation, which now includes countries accounting for 97% of global emissions, compared with the 14% that are covered by the current, second commitment period of the Kyoto Protocol.

But adequate scope of participation is only one of two necessary conditions; the other is adequate collective ambition.  Unfortunately, the fundamentally voluntary nature of the NDCs – which is precisely what facilitated the exceptionally broad scope of participation – works against adequate ambition to address this global commons phenomenon, which is plagued by free rider problems.

The Challenge for Climate Negotiators

This raises the key overall challenge that faced the negotiators in Bonn in May and will face them in Katowice, Poland, in December (at the Twenty-Fourth Conference of the Parties of the United Nations Framework Convention on Climate Change):  What can they do, when writing rules to put flesh onto the skeletal Paris Agreement, to encourage countries to increase their ambition over time?  That’s where carbon markets and cooperation among jurisdictions potentially come in.

International Cooperation under the Paris Agreement

Largely because cooperation among jurisdictions — including through carbon markets — can lower abatement costs, such cooperation may be essential for the ultimate success of the Agreement.  This cooperation might take the form of international linkage, where by “linkage,” I mean connections among policy systems that allow emissions reduction efforts to be redistributed among those systems.

Such linkage is typically framed as between cap-and-trade systems, but regional, national, and sub-national policies are and will be highly heterogeneous, including not only cap-and-trade, but offset systems, carbon taxes, performance standards, and technology standards.  Note that we already see this sort of heterogeneity within the European Union’s own set of climate change policies, as well as within California’s suite of climate initiatives.

The good news is that linkage among highly heterogeneous policies is eminently feasible, as I have written about previously in this blog, drawing on my research with Michael Mehling (MIT) and Gib Metcalf (Tufts University).  The even better news is that one part of the Paris Agreement provides a potential home for such international cooperation, linkage, and carbon markets – Article 6.  (If you are interested in the details, I recommend a recent report from the Asian Development Bank, “Decoding Article 6 of the Paris Agreement.”)

The Promise and Problems of Article 6

In the negotiations that led up to the 2015 Paris climate talks, it was by no means clear what role — if any — market mechanisms would play in the Paris Agreement.  In the negotiations, the European Union, Brazil, and other countries played crucial roles in generating the compromise that became Article 6 of the Agreement.

That compromise resulted in text that — to put it kindly — is very much subject to interpretation.  Now, as Benito Müller, Kelley Kizzier, and their colleagues have observed, intentional vagueness and ambiguity of text can be quite helpful in achieving a negotiated compromise, but such vagueness is decidedly not helpful when it comes to making an agreement operational.

This compromised home for markets emerged in Article 6 despite the entrenched opposition of a small set of vocal countries — including some Latin American socialist economies (the so-called ALBA coalition) — who wanted nothing of the kind to appear in the Paris Agreement.  They succeeded in keeping the word “market” out the Paris Agreement, but the concept and the potential reality is very much there!  (Ironically, at their insistence, the phrase “non-market” does appear in the Agreement.)

In any event, provision for markets and international cooperation is implicit in Article 6.2, which allows for cooperative approaches involving Internationally Transferred Mitigation Outcomes (or ITMOs), which are vague and without definition, but can function as an international accounting mechanism for international trades, exchanges, and cooperation.  And Article 6.4 establishes a more centralized mechanism to contribute to emissions mitigation and support sustainable development, essentially as a successor to the Clean Development Mechanism (and may soon come to be called the “Sustainable Development Mechanism” or SDM).

Advantages and Concerns about Cooperation and Linkage

Despite the opposition I mentioned, most parties to the Paris Agreement are supportive of cooperative approaches (and more than half explicitly mentioned carbon markets in their respective NDCs).

This may be because of six important advantages of such cooperation:  first, cost savings by allowing firms to take advantage of lower cost abatement opportunities in other jurisdictions; second, reducing market power of individual firms by enlarging the market’s scope, and reducing total price volatility by thickening markets; third, political benefits to Parties, by providing a sign of “momentum” as jurisdictions band together, possibly influencing other parties to participate; fourth, administrative economies of scale through knowledge sharing in design and operations, as well as shared administrative and oversight costs; fifth reducing leakage and competitiveness impacts by harmonizing the shadow price of carbon across jurisdictions; and sixth, allowing for the achievement of the UNFCCC’s critical principle of “Common but Differentiated Responsibilities” without sacrificing cost-effectiveness.

There are also real concerns about linkage:  first, distributional impacts within and across linked jurisdictions; second, automatic propagation of certain design elements, in particular, cost-containment elements (banking, borrowing, and price collars); and third, decreased national autonomy.

Back to the Article 6 Negotiations and International Policy Linkage

Article 6 can be a home both to linkage of the sort we usually talk about, as well as “soft linkage,” such as an agreement — explicit or implicit — to harmonize carbon prices either at some level or within overlapping bands.

Thinking about the UNFCCC negotiations taking place now, most types of heterogeneity – of policy instruments, level of political jurisdiction, and nature of NDC targets – do not present insurmountable obstacles to linkage, but some do present real challenges, and indicate the need for specific guidance as the rulebook of the Paris Agreement is written.

Unfortunately, some countries want the Article 6 guidance to go beyond fundamental issues of accounting and environmental integrity to broader matters of environmental ambition, which properly belong in other parts of the Paris Agreement.  Whereas, accounting provisions to avoid double-counting of NDC actions through ITMOs surely belong in the Article 6 rulebook, some countries have proposed, for example, that all ITMO exchanges themselves must actually reduce net emissions.

This sounds very much like the U.S. Environmental Protection Agency’s 20% rule in its 1970’s Emissions Trading Program, which required that net emissions fall by 20% with each trade.  This was a tax and an inhibition on trading, and the result was that virtually no trading occurred.  This reminds me of a corrupted version of George Santayana’s admonition that those who do not learn from history are doomed to repeat it.  Instead we have, “I’ve learned from my mistakes, and I can repeat them exactly the same again.”

The general problem is that if the guidance extends much beyond basic accounting rules, then restrictive requirements could actually impede effective cooperation.  True to the nature and spirit of the Paris Agreement, less can be more!

UNFCCC Update from Bonn

I closed my dinner comments in Florence with a brief update on the negotiations that concluded the previous week in Bonn.  The two weeks of meetings of the Article 6 group were reported to be much tougher than they had been previously, yet the progress on the Article 6 work is actually ahead of that of groups focused on other parts of the Paris Agreement.  Although positions on Article 6 are hardening, there is no clear blocking party or coalition (unlike in the work on some of the other parts of the Agreement).  There may be less resistance to agreement simply because participation in Article 6 instruments would ultimately be voluntary.

The Path Ahead

So, as the negotiations proceed, a combination of common accounting rules and an absence of restrictive conditions can accelerate linkage, allow for broader and deeper climate policy cooperation, facilitate the emergence of a robust global carbon market, and – most important – increase the latitude of the Parties to the Paris Agreement to scale up the ambition of their long-term contributions to global greenhouse gas emission reductions.

Whether that will come to pass, we simply do not know as of now.  As usual, only time will tell.

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