The Future of U.S. Carbon-Pricing Policy

In 2007, I was asked by the leaders of the Brookings Institution’s Hamilton Project to write a paper describing a national emissions trading system to reduce U.S. carbon dioxide (CO2) emissions to help address the threat of global climate change.  I responded that I would prefer to write broadly about carbon-pricing instruments, including what I considered to be the symmetric instruments of a carbon tax and a carbon trading program.  But the Hamilton Project leaders said no, they would find someone else to write about carbon taxes (which turned out to be Gib Metcalf), and they wanted me to “make the strongest case possible for” what is today called a cap-and-trade system.  I did my best, and in the process I came to be identified – and to some degree may have become – an advocate for CO2 cap-and-trade.  For better or for worse, during the Obama administration transition, the design recommendations in my Hamilton Project paper became one of the starting points for efforts to structure the administration’s proposed CO2 cap-and-trade system that became part of the failed Waxman-Markey legislation, H.R. 2454, the American Clean Energy and Security Act of 2009.

More than a decade later, I have written a new paper in which I seek to approach this question as I wished to in the first place, treating both instruments in a balanced manner, examining their merits and challenges, without necessarily favoring one or the other.  On May 16, 2019, I presented this new paper at the National Bureau of Economic Research’s first annual Environmental and Energy Policy and the Economy Conference, held at the National Press Club in Washington, D.C.  My topic was, “The Future of U.S. Carbon-Pricing Policy.”  (It will be forthcoming in Environmental and Energy Policy and the Economy, volume 1, edited by Matthew Kotchen, James Stock, and Catherine Wolfram, published by the University of Chicago Press.)  In today’s blog essay, I provide a very brief summary of the paper, based upon the presentation I made at the NBER conference.  I hope you will find this of sufficient interest to download and read the complete paper.

Premises, Questions, and Conclusions

I began this research with two major premises:  first, that economists and most other policy analysts agree that carbon-pricing will likely be a necessary (although not sufficient) part of any meaningful, long term U.S. climate change policy, because of:  (1) feasibility – the necessity of affecting millions, indeed hundreds of millions, of decentralized decisions; (2) cost-effectiveness, given the tremendous heterogeneity of marginal abatement costs; and (3) the importance of providing incentives for carbon-friendly technological change.  My second premise was that there is much less agreement among economists (and other policy analysts) regarding the choice of specific carbon-pricing policy instrument – carbon tax or cap-and-trade.

This prompts two questions:  (1) how do the two major approaches to carbon pricing compare on relevant dimensions, including but not limited to efficiency, cost-effectiveness, and distributional equity?  (2) Which approach is more likely to be adopted in the future in the United States?

Having carried out an exhaustive examination, two major conclusions stand out (among others).  First, that the specific designs of carbon taxes and cap-and-trade are more consequential than the choice between the two instruments.  And second, that political feasibility affects the normative merits of the two instruments, and vice versa.

Similarities & Symmetries

Of fourteen separate issues I examine, some appear at first to be key differences (in theory), but many of these differences fade on closer inspection, and depend on specifics of design.

First of all, carbon taxes and commensurate cap-and-trade turn out to be perfectly equivalent in regard to:   (a) incentives for emission reduction (both can be upstream on the carbon content of fossil fuels); (b) aggregate abatement costs (both can be cost-effective, both provide the same incentives for technological change, and both can utilize offsets to further lower aggregate abatement costs); and (c) effects on competitiveness (both can lessen these impacts via appropriate border adjustment mechanisms).

Next, the two instruments are nearly equivalent in regard to possibilities for raising revenue (cap-and-trade can utilize auctions, but given the structure of Congressional committees, revenue recycling may be easier with taxes).

And these instruments are similar in regard to:  (a) costs to regulated firms (cap-and-trade systems can freely allocate allowances, and taxes can provide inframarginal exemptions below a specified level of emissions); and (b) distributional impacts (the two instruments can be designed to be roughly equivalent in this regard).

Differences & Distinctions

Beginning with the least significant differences, there are relatively minor distinctions in terms of transaction costs (decreasing marginal transaction costs in cap-and-trade systems – such as with volume discounts on brokers’ fees – can violate the independence property, whereby the equilibrium allocation of allowances and hence aggregate costs are ordinarily independent of the initial allocation).

There are more meaningful, but still subtle differences with regard to:  (a) performance in the presence of uncertainty (for this, I urge you to read at least this section of the complete paper, because new research suggests that the implications of the classic Weitzman rule in the presence of a stock externality are moderated – if not reversed – due to the persistent effects of technology shocks, which foster positive correlation between marginal benefits and marginal costs); and (b) linkage with other jurisdictions (it is easier with cap-and-trade systems, but tax systems can also be linked).

That said, there are significant differences between the instruments in terms of:  (a) carbon-price volatility (a problem only with cap-and-trade systems, but a problem that can be mitigated with price collars and banking of allowances); (b) interactions with complementary policies (a significant issue with cap-and-trade systems, which is much less severe with carbon taxes, because the “waterbed effect” is eliminated); (c) market manipulation (there is a need for regulatory oversight in cap-and-trade systems, but tax evasion is a parallel issue in tax systems, although presumably less severe in the U.S. context); and (d) complexity and administrative requirements (cap-and-trade is certainly more complex and has greater administrative requirements, but one might ask whether a simple tax will remain “simple” as it works its way through the Congress).

Hybrid Policy Instruments and a Policy Continuum

Many of the remaining differences can diminish further with implementation.  Indeed, hybrid policies which mix features of tax and cap-and-trade blur distinctions.  For example, auctioning of allowances and the use of price collars bring cap-and-trade closer to a tax system; and quantity formula employed to adjust a tax, and the use of tax revenues to mitigate emissions bring a tax closer to cap-and-trade.  The result is that the dichotomous choice between a carbon tax and cap-and-trade can become a choice of design elements along a policy continuum, and the design of these instruments can be more consequential than the choice between the two.

Which is More Likely to be Adopted – Taxes or Trading?  Positive Political Theory

Framing this question in terms of the metaphor of a political market, it is helpful to think about political demand and political supply of policy instruments.  In terms of the demand from interest groups, first, regulated industry may oppose an ordinary tax approach, as it typically leads to greater costs than the simplest cap-and-trade (or than a performance standard, for that matter), because private industry is paying not only for compliance costs, but also for the tax on residual emissions.  Second, regulated industry may favor cap-and-trade, because it conveys scarcity rents to firms, and can provide entry barriers for potential new entrants, which can make the rents sustainable.

Environmental advocacy groups favor cap-and-trade, due to the emissions certainty it provides, but also because presumably they have a preference for policies that help obscure costs, and cap-and-trade does a better job of sweeping discussion of costs under the rug than does a tax.  However, in the era since cap-and-trade was demonized as “cap-and-tax,” this difference may be much less than it was!

Turning to the supply side (within the legislature), the revenue from either a tax or auctioning of allowances can be attractive to government.  And because of the independence property of cap-and-trade, legislators can allocate allowances to build political support without increasing the costs or reducing the effectiveness of the policy.  Of course, this important political advantage becomes an economic disadvantage if it invites particularly harmful rent-seeking behavior.  Finally, environmental policy makers tend to think in terms of pollution quantities, not prices.

Experience with Carbon Pricing:  Emissions Coverage & Price in Implemented Initiatives

            There are some fifty carbon-pricing systems in operation worldwide, with equal numbers of carbon taxes and carbon cap-and-trade systems.  A quick comparison of these policies reveals two striking realities.  First, the highest carbon prices (the height of the bars in the figure below) are for carbon taxes (in norther Europe).  Second, the scope of coverage (the width of each bar in the figure) of cap-and-trade systems greatly exceeds that of carbon taxes.  Putting the two features (severity and scope) together, a reasonable measure of the relative importance of the policies is given by multiplying the carbon price (tax level or market price of allowances) by the tons of coverage, that is, the respective areas in the figure.  On this basis, it appears that political revealed preference has been weighted toward cap-and-trade (at least up until now).

Carbon Price & Emissions Coverage of Implemented Carbon-Pricing Initiatives

Which Has Worked Better – Experiences with Trading and Taxes

Based upon more than thirty years of experience with cap-and-trade systems, including but not limited to CO2 programs, lessons regarding the design and efficacy of these systems can be drawn.  In brief, there is empirical evidence for the following:  cap-and-trade has proven to be environmentally effective and economically cost-effective; downstream, sectoral programs have been common, but economy-wide upstream systems are feasible; transaction costs have been low to trivial; a robust market requires a cap below business-as-usual; banking has been exceptionally important, representing a large share of the gains from trade; price collars are very beneficial; free allocation of allowances fosters political support, with a likely transition to greater auctioning over time; competitiveness impacts can be mitigated with an output-based updating allocation; “complementary policies” are common, but in some cases can have perverse consequences, including no additional emissions reduction, an increase in aggregate costs, and suppressed allowance prices.

Turning to experiences with carbon taxes, two applications stand out.  First, there are the northern European carbon tax systems, initiated in the 1990s in Norway, Sweden, Denmark, and Finland.  Typically these were elements of broader energy and excise tax reform initiatives, and some are at the highest levels of any carbon-pricing regimes worldwide.  However, fiscal cushioning has been common for industries expressing concerns.  That said, these taxes have raised significant revenues to finance spending or to lower other tax rates, but unfortunately, there is little empirical evidence of their emissions impacts.

More striking is British Columbia’s carbon tax, initiated in 2008, which comes closest to that recommended by economists.  Currently, it is an upstream tax of $27/ton of CO2, but with important exemptions in place for key industries.  Importantly, 100% of tax revenue was originally refunded through general tax rate cuts, but over time, there has been more focus on tax cuts for specific sectors and locations.  Although there is some debate in the literature, it appears to have been effective in reducing emissions.

Empirical Evidence for Positive Assessment

Given that the normative differences between the two instruments are minimal, a key question becomes which instrument is more politically feasible, and which is more likely — in practice — to be well designed.  Based on experiences with cap-and-trade and carbon taxes, the relative masses in the figure above suggest that political revealed preference has favored the former.  Furthermore, after years of deliberation, China has chosen trading for its national program (although it appears to be a set of sectoral tradable performance standards, not a true, mass-based cap-and-trade system).  In addition, the new “Transportation and Climate Initiative” in the northeast United States was first proposed in terms of fuel taxes but is gravitating toward cap-and-trade.  Also, New Jersey is preparing to rejoin the Regional Greenhouse Gas Initiative, and Oregon is poised to enact an economy-wide CO2 cap-and-trade system this year.  On the other hand, Washington State has twice defeated a carbon tax.

But past may not be prologue.  The demonization of the Waxman-Markey trading system as “cap-and-tax” may have reduced the political advantage of cap-and-trade (that it can hide the costs).  And there is clearly increasing interest in a national carbon tax in the policy world, including several bills in Congress and the prominent Climate Leadership Council proposal.  On the other hand, the “Green New Deal” is silent about carbon-pricing of any kind.

It is worthwhile focusing on the political economy of the British Columbia carbon tax.  Its successful enactment has been attributed to “the confluence of political conditions ripe for carbon taxation”:  untapped hydroelectric potential; a strongly environmentalist electorate (as in the case of California’s move to cap-and-trade with Assembly Bill 32); a right-center government with trust from the business community (as with the George H.W. Bush administration’s SO2 allowance trading system in the Clean Air Act amendments of 1990); and a premier with institutional capacity to pursue personal policy preferences.  There has been increasing public support over time, due to the perception of emissions reductions without severe economic impacts, but political pressures have caused the evolution of the system from using revenues exclusively to cut distortionary taxes to greater use of tax cuts to favor specific sectors and regions.

Clearly, political pressures can drive up social costs with either type of carbon-pricing instrument.  On the one hand, politics may disfavor the auctioning of allowances in cap-and-trade systems, while, on the other hand, politics may disfavor cost-effective cuts of distortionary taxes in tax systems.

Does Either Carbon-Pricing Instrument Dominate in Normative or Positive Terms?

When carbon taxes and cap-and-trade are designed to be truly comparable, their characteristics and outcomes are similar, and in some cases fully equivalent (normatively), in terms of their:  emission reductions, abatement costs, revenue raising, costs to regulated firms, distributional impacts, and competitiveness effects.  But on some other dimensions, there can be real differences in performance.  The tax approach is favored by administrative requirements, interactions with complementary policies, and effects on carbon-price volatility; whereas cap-and-trade is favored by linkage with policies in other jurisdictions, and possibly by anticipated performance in the presence of uncertainty.  In the positive political economy domain, the evidence is also decidedly mixed.  Hence, there is not a strong case for the blanket superiority of either instrument.  Differences in design simply dominate differences between the instruments themselves.

Can Carbon-Pricing be Made More Politically Acceptable?

The track record of 50 carbon-pricing policies cited above should be contrasted with the 176 countries with renewable energy policies or energy efficiency standards, as well as another 110 national and sub-national jurisdictions with feed-in tariffs.  Hence, carbon pricing has not in general been the favored approach to climate change policy.  Why is this the case?  Survey and other evidence indicates that public perceptions – some of which are inaccurate – are primary factors behind aversion to carbon taxes:  “personal costs too great; policy is regressive; could damage economy; will not discourage carbon-intensive behavior; and government just want the revenues.”  So, one way to improve public acceptance could be through better information, that is, education.

But another way forward could be through judicious policy design, which may well depart from first-best design, including:  phasing in taxes/caps over time (which was effective in California and British Columbia); earmarking revenues from taxes/auctions to finance additional climate mitigation, in contrast with optimizing the system via cuts in distortionary taxes; and/or using revenues for fairness purposes, such as with lump-sum rebates or rebates targeted to low-income and other particularly burdened constituencies (a carbon tax with “carbon dividends” or a cap-and-trade system in the form of “cap-and-dividend”).

Has the Defeat of National CO2 Cap-and-Trade Initiatives Provided Openings for Carbon Tax Proposals?

Political polarization has decimated the key source of Congressional support for environmental/energy action, the political middle.  And the successful political battle against the Obama administration’s CO2 cap-and-trade legislation featured the effective demonization of that instrument as “cap-and-tax.”  Does the consequent reputational loss for cap-and-trade provide a meaningful opening for the other carbon-pricing instrument – a carbon tax?

It would seem that large budgetary deficits ought to increase the attraction of new sources of revenue, but existing carbon tax proposals have largely been revenue-neutral.  That said, it is surely true that there has been increased attention to carbon taxes from the “policy community,” with support coming not just from Democrats, but also from prominent Republican academic economists and former Republican high government officials.  But – finally – what about in the real political world of those currently holding elective office in the federal government?

It is presumably good news for carbon tax proposals that they are not “cap-and-trade.”  Perhaps that helps with the political messaging.  But if conservative opposition could tarnish cap-and-trade as “cap-and-tax,” surely it will not be difficult to label a tax as a tax!  And in addition to such opposition from the political right, it is – as of now – questionable whether the new left will want a carbon tax to be part of its “Green New Deal.”

Hence, in the short term, national carbon pricing of either type will likely continue to face an uphill battle.  Therefore, in addition to considering second-best carbon-pricing design (as I recommended above), economists can work productively to catch up with political realities by considering better designs of second-best non-pricing instruments, such as clean energy standards.

But, at some point the politics will change, and it is important to be ready, which is why – for the longer term – ongoing research on carbon-pricing is very much warranted, particularly if it can be carried out in the context of real-world politics, and focus on policies that are likely at some point to prove feasible.


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.

A video of the entire event is available here.

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,


                                                      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.


California’s Crude Oil Production and its Climate Change Policies

California is among the most aggressive jurisdictions in the world in its pursuit of public policies to reduce its emissions of greenhouse gases (GHGs), linked with climate change. At a time when the Trump administration in Washington is working to reverse the Obama administration’s climate policy achievements, California and other sub-national entities are taking the lead in the development and implementation of meaningful domestic policies to mitigate the impact of human activity on the climate.

At the same time, California is a producer of crude oil.  Is this inconsistent, or even counter-productive?  In a recent report, advocates have criticized Governor Jerry Brown, and proposed a ban on crude oil production within the State, in furtherance of California’s climate policies.  The thinking goes, crude oil production leads to environmental impacts, so how can it be allowed?

The logic is flawed, and the prohibition – if adopted – would impose tremendous costs on the State with little or no environmental benefit.  As California has developed its climate policies, the need to balance the benefits of these policies with their economic and human consequences has always been a challenging issue.  Achieving aggressive climate goals will not be cheap, so designing sensible, effective policies is critical.  Simply adopting any and all restrictions that might achieve some emission reductions would unnecessarily raise the human cost of limiting GHG emissions.  This is no doubt obvious to some readers of this blog, but for others, let me explain.

At its heart, the climate problem arises because of CO2 emissions associated with the use of energy and related services.  We heat our homes in the winter and cool them in the summer using electricity and natural gas.  We use gasoline to get to work and take vacations.  As each country or state – including California – tries to reduce its GHG emissions, the policies and regulations adopted to achieve this end nearly always target the activities that lead to GHG emissions – the generation of electricity, the use of transportation, and the heating of living spaces.

The proposed ban on crude oil extraction would flip this on its head, focusing instead on the supply of a fossil fuel.  But the simple reality is that the sources of fossil fuel supply are so ubiquitous that crude oil from other regions of the world will replace supplies from California, if California chose not to supply its own on-going needs.  Oil and gas used to heat homes and to power vehicles comes not only from California, but from most every region of the globe.  Many of these regions have expanding supplies of crude oil due to technological improvements, including the Bakken shale of North Dakota, and vast supplies available with relatively little effort, such as in the Middle East.

Advocates claim that reduction of California crude oil production would reduce global consumption of crude – a claim of questionable validity.  But that is not even the right question.  There are many things that can be done to reduce GHG emissions, and a sensible, affordable, and sustainable policy will be one that achieves reductions at the lowest cost.  Even if restricting California’s oil production might reduce global crude consumption, California would certainly bear all of the economic consequences of this policy, as the state would then rely solely on crude oil imports.

In fact, a restriction on California’s crude production is unlikely to reduce GHG emissions within California. The State’s total GHG emissions are limited by the cap of California’s GHG cap-and-trade system.  The most a restriction on California’s crude production can do is to increase costs, while achieving little or no incremental improvement in GHG emissions.

Moreover, supply-side restrictions can limit technological progress that can have very positive economic and environmental consequences.  The same advocates oppose shale “fracking,” but the innovative combination of hydraulic fracturing and horizontal drilling has led both to tremendous economic benefits by expanding supplies of low-cost domestic energy and reducing energy imports, and to environmental benefits by allowing lower-carbon natural gas to displace higher-carbon coal in the generation of electricity across the United States.

By focusing on policies aimed at achieving the appropriate policy goal of reducing GHG emissions – rather than trying to choose winners and losers among technologies and energy sources used to achieve those goals – California can achieve its climate policy goals in ways that are environmentally effective, economically sensible, and ultimately sustainable.  In my view, Governor Brown merits compliments rather than criticism for California’s progressive environmental and energy policies.


In the past, I have periodically advised the Western States Petroleum Association (WSPA), although on a very different issue, namely the design of California’s CO2 cap-and-trade system.  That was about two years ago, and neither WSPA nor any of its member companies are aware of my writing this essay.  As always in this blog, I am expressing my personal views, and not speaking on behalf of any of the institutions, organizations, or firms with which I am or have been associated.