E7: TIL about carbon pricing


What exactly is a carbon price, and how does it work? What would it look like and how would it change everyday life? In this episode of TILclimate (Today I Learned: Climate), MIT economics professor Christopher Knittel joins host Laur Hesse Fisher to break down the complexities of carbon pricing. Together, they explain different types of programs, give us a sense of how much it would cost, and explore how countries and U.S. states are experimenting with carbon pricing now.

Christopher Knittel is a professor of applied economics at MIT’s Sloan School of Management, director of the MIT Center for Energy and Environmental Policy Research (CEEPR), and co-director of the MIT Electric Power Systems Low Carbon Energy Center. Prof. Knittel’s research focuses on energy and environmental economics, and he works to compare the efficiency and costs of different programs and policies that aim to reduce greenhouse gas emissions.

For more climate explainers, check out: www.tilclimate.mit.edu.


Special thanks to Tom Kiley and MIT Open Learning.
Produced by the MIT Environmental Solutions Initiative at the Massachusetts Institute of Technology.

CK: [00:00:00] You don't require the government to be heavy-handed. Or to even know how firms and consumers are going to reduce pollution. You let the market figure it out.

LHF: [00:00:16] Welcome to TILclimate, the show where you learn about climate change with real scientists. I’m your host Laur Hesse Fisher from the MIT Environmental Solutions Initiative.

You might have heard about something called a carbon tax or cap and trade, or putting some kind of price on carbon dioxide emissions. Today, we’re going to break down what all that means and why carbon pricing is so commonly talked about.

To do this, I connected with MIT’s Prof. Christopher Knittel.

CK: [00:00:45] I'm the George Shultz Professor of Applied Economics in the Sloan School of Management. I also direct the Center for Energy and Environmental Policy Research

LHF: [00:00:57] The first question I have for you is why even talk about carbon pricing?

CK: [00:01:03] Yeah. I think the short answer to that is that it's free to put greenhouse gases in the air even though they cause cost to society. So in order to fix the market, you can charge, whether it's firms or customers, the damage that they're doing when they emit those greenhouse gases in the air and the most direct way you could put a price on the pollutant is by taxing it directly.

LHF: [00:01:31] This is the first kind of carbon pricing, called a carbon tax. You can emit as much as you’d like, you just have to pay for it. It makes products and services that emit a lot of CO2 more expensive, incentivizing companies and people to innovate and to choose less-polluting options. If you want the market to emit less CO2, you raise the tax.

One of the big debates is what would happen to the money that’s collected from a carbon tax.

CK: [00:02:01] You could have a plan which taxes carbon dioxide, takes the money into the government coffers, and then redistributes that money on a per capita basis in some way. Alternatively, you can tax carbon dioxide, collect the money and use it to subsidize solar panels or so on.

LHF: [00:02:19] So the collected tax money could help support some kind of program, like investing in technologies that suck CO2 out of the atmosphere or to help towns prepare for climate change. Or the collected tax money could also be given back to people to help them pay for the increased cost of energy.

That’s a carbon tax… There’s also something called a “cap and trade” system.

CK: [00:02:46] A cap and trade system is slightly different although it also leads to a price on the pollutant. What a cap and trade system does is the government caps the amount of the pollutant that is allowed to be released into the atmosphere. And then the second step is to issue permits that allow whoever's holding that permit to emit say a ton of carbon dioxide in the atmosphere, and also allows that holder of the permit to sell it if they wanted to. And that's the trade part of cap and trade.

LHF: [00:03:21] This kind of carbon pricing is kind of like how hunting permits work. A state park sets limits on how much game can be hunted and then issues permits to people who want to hunt them. And if the state park wanted to protect more game, then they could lower the number of permits that are for sale.

Now with cap and trade, you could actually sell and buy permits on a market. So if your company didn’t emit as much carbon dioxide, you could sell your permit to another company; or if you wanted to emit more, you could buy one from someone else.

CK: [00:03:56] Whoever holds onto or has one of those permits has a valuable asset that they can sell or use themselves.

LHF: [00:04:03] Let's get real here. If a carbon price were to be implemented tomorrow, people are going to see gas prices go up. They're going to see their home energy prices go up. They're going to see other things go up. What would our new world look like?

CK: [00:04:17] Yeah, the average American emits or buys products that lead to about 20 tons of CO2 in the atmosphere. So a $40 carbon tax would be about $800 burden per person per year.

LHF: [00:04:33] That's pretty substantial.

CK: [00:04:34] It’s... And a lot of my work focuses on understanding how carbon taxes impact low income consumers. So it's not something we can just sweep under the rug, it's real. But I come back to the fact that a carbon tax generates that same amount of money per person per year.

So what a plan would look like is that the average person would be taxed $800 per year, but then the average person would also receive $800 check per year. Now, you might ask yourself, "well then. What does it do? Why how does that have any impact?" And the reason why it has an impact is that if there's something I can do to reduce my greenhouse gas burden, I know I'm going to get get that much money back in the the following year. That is if I somehow am able to go from instead of emitting 20 tons to 10 tons, then I'm going to be able to save $400 per year if the carbon tax is $40.

So I'm going to have an incentive to change the thermostat slightly during the winter or the summer. Anything I can do to reduce my carbon footprint, I'm going to pocket that cash. And that's going to lead to a lot of behavioral changes that don't exist absent that carbon tax.

LHF: [00:05:55] Now, a $40 carbon tax is just an example. There are proposals in the US being discussed that are calling for prices ranging from $12.50 a ton to $50 a ton.

Of course, there are a lot of people who don’t want to see more taxes. And companies who don’t want their products and services to become more expensive. I mean, not many of us want to pay for something that used to be free.

A carbon price would, at least initially, create a cost that society would have to agree is worth it. Because a lot of the things we use and do now would cost more, until we change to buying products and services that produce less CO2.

It’s worth noting that the U.S. federal government did something like this in the past.

LHF: [00:06:42] In the 1980s, the U.S. implemented a program under President George Bush to limit pollutants that were causing asthma, premature deaths, and hurting our waterways and forests. One of these pollutants is sulfur dioxide, which is also called SO2.

CK: [00:06:58] When SO2 pricing came about, what that did is it increased the cost of burning high-sulfur coal. Now it turned out that there was this very cheap way to reduce SO2 emissions and that was to switch from high-sulfur coal to low sulfur coal. So in the absence of that SO2 Market, a lot of the policy discussions were going to require power plants to adopt these very expensive technologies to take the SO2 out of the emissions as opposed to switch to the type of coal. And had we gone down that path we would have spent a lot more money under that where you tell power plants what to do rather than let the market incentivize them to find the cheapest way to reduce SO2 emissions.

So you don't require the government to be heavy-handed. Or to even know how firms and consumers are going to reduce pollution. You let the market figure it out. That led to a much cheaper alternative than what anybody ever envisioned.

LHF: [00:08:10] In fact, pricing pollution is generally considered by both liberal and conservative economists as the most cost-effective way to reduce that pollution.

CK: [00:08:21] Researchers including myself have done a lot of research comparing alternatives to carbon taxes to reduce CO2 emissions and there's many, whether it's subsidizing electric vehicles, or subsidizing solar panels, or requiring a certain number of electric vehicles to be bought and sold. And that research suggests that those alternative policies are often up to 10 times more expensive, which means leveraging those policies for a given amount of money society is spending we're not reducing as much pollution as we could.

LHF: [00:09:02] Carbon pricing can be a contentious subject. It would force entities -- like energy and manufacturing companies, who emit a lot of carbon dioxide -- to start paying for that. That’s a big shift in our economy and it could cost a lot of money upfront, but also could be a very effective way for reducing emissions.

Countries around the world and even U.S. states are already experimenting with carbon pricing.

There are a bunch of cap and trade programs out there: the European Union has one, the state of California has one, a collection of Northeastern states also have a regional cap and trade system. And China has one scheduled to start in 2020.

Right to the north of the United States., there’s the province of British Columbia, in Canada. They implemented a carbon tax program that sent checks before the tax started to each resident to help them adjust to the increased costs.

There is a ton more that we didn’t cover in today’s episode, but I hope we’ve given you at least an overview of what carbon pricing is about.

You might have a lot more questions about this so feel free to send them to us on Twitter @TILclimate or email us: tilclimate@mit.edu

In our show notes and on Twitter, we’ll include some other resources that you can dig into, including a map where you can look at carbon pricing programs around the world and a quick list of carbon pricing proposals that on the table in the United States.

What questions do you still have? Send us your comments and questions on Twitter @TILclimate.

Thanks for joining today. I’m your host Laur Hesse Fisher from the MIT Environmental Solutions Initiative. Thank you to Prof. Knittel for speaking with us and thank you for listening. We’ll see you next time.

An educator guide for this episode can be found below. 

For more information on carbon pricing, check out:

The work of Prof. Knittel:

Overviews of carbon pricing:

Examples of carbon pricing policies outside of the U.S.:

Examples of carbon pricing policies in the U.S.:

About the US sulfur dioxide (SO2) cap and trade program

An overview of climate change:


Educator Guide

Created by Olivia Burek, Alyssa Farkas, and Aaron Krol, with thanks to Sarah Hansen and MIT Open Learning


The following questions can be used to encourage your students to reflect on, extend, and apply what they’ve learned from the podcast episode. Re-use and remix them as writing prompts, discussion guides, or ideas for project-based learning in your classroom.


Critical Thinking 

  • How would carbon pricing affect your current way of life? How might your community be positively or negatively affected by such a system, and why? How might consumers be affected in your community? And businesses? How could we make a carbon pricing system equitable and fair to groups of all socioeconomic statuses? How might other regions be affected differently from your own? If implemented on an international scale, should certain areas or countries adopt more of the burden than others? If so, why?
  • Who are the key people or groups involved in making decisions about carbon pricing in your city? How about in your state? Who should be consulted in order for the most economically optimal decision to be made? How about the most socially optimal?
  • Imagine your city or town were considering creating a new price on carbon emissions. Who might support this policy? Who might oppose it? What are the major challenges to cooperation between different stakeholders and policymakers in your town? Are these the same or different from the challenges to cooperation between different states in the U.S., or between different countries? How could you go about negotiating a compromise in each of these contexts? How might different solutions be more effective in different locations?


  • Many countries, such as Canada, Australia, the U.K., China, and parts of the U.S. have implemented some form of carbon pricing. Research one of these existing carbon pricing systems. What were the goals of the policy? How has it succeeded or failed in meeting those goals? How has it changed since being implemented? What other initiatives is this government taking to combat climate change, if any? If the policy generates revenue, what is done with that revenue? How do you think these factors have affected the success of the program? 
  • What do existing carbon pricing systems have in common? Compare and contrast two or more systems. How have different carbon pricing schemes varied by pricing structure, location, or application? Have differences between these policies contributed to different results?
  • A cap-and-trade scheme for sulfur dioxide (SO₂), known as the Acid Rain Program, was introduced as an amendment to the Clean Air Act in 1990. Research how this program worked, why it was created, and what the outcomes were. Why have similar programs not been attempted for other types of pollutants, like greenhouse gases? What, or who, is preventing the formulation of such programs?
  • Who makes the decisions regarding carbon pricing in your region? What kinds of policies have been made, or proposed, thus far? How can you share your opinion about carbon pricing with decision makers?


  • Have you heard of carbon pricing before? Do you think it’s a useful method to combat climate change? Why or why not? Do you think it will become more widespread in the future? Do you support it?


  • Host a mock town hall forum to discuss a carbon pricing system being proposed by a candidate in your district. The roles may include: the candidate proposing the system, one or more other candidates in the district, and constituents of varying political ideologies. 
  • Debate: one group in favor of a carbon tax vs. one group in favor of a cap-and-trade program
  • Debate: one group in favor of carbon pricing vs. one group in favor of non-market-based (command-and-control) policies
  • Have a round table discussion about the proposed implementation of an international carbon pricing system (carbon tax, cap-and-trade, or undecided). Each student may be a spokesperson for a different country. Be sure to have representatives of countries in different parts of the world, as well as of varying levels of wealth/development, and countries that already have carbon pricing vs. those that don’t.


The following infographic was used to develop many of the critical thinking questions in this guide. You may also find it helpful:
Watanabe-Crockett, L. (2016, December 12). The critical thinking skills cheatsheet [Infographic]  [Web log post]. Retrieved May 1, 2019, from https://www.wabisabilearning.com/blog/critical-thinking-skills-cheatshee...


Need additional open educational resources related to the topics of planes and climate change? You may find these free teaching materials from MIT OpenCourseWare (ocw.mit.edu) helpful: 

Environmental Policy and Economics
Level: Undergraduate
This course, taught by Dr. Hunt Allcott, explores the role of government in the regulation of the environment and helps students develop the tools to estimate the costs and benefits of environmental regulations, including the costs of measures to prevent or mitigate climate change in the U.S. and worldwide. Educators have access to the reading list, lecture slides, and PDF versions of the lecture notes and assignments.
Global Climate Change: Economics, Science, and Policy
Level: Graduate
This course, taught by Professors Henry Jacoby, Ronald G. Prinn, and Mort Webster, introduces scientific, economic, and ecological issues underlying the threat of global climate change, developing an integrated approach to the analysis of climate change processes and the assessment of proposed policy measures. Educators have access to the reading list and to PDF versions of the lecture notes and problem sets.
Planning Economics
Level: Graduate
This course, taught by Professor Frank Levy, applies microeconomic theory to issues that markets don't always handle well and so are not usually covered in a standard microeconomics course. Educators have access to PDF versions of the recitation notes, problem sets with solutions, and the final exam, as well as links to related resources, including the professor’s own website explaining the fundamental concepts of economics.