As part of his climate agenda, President-elect Joe Biden promises to pass legislation that “establishes an enforcement mechanism” to curb harmful greenhouse gas emissions. What this means is far from clear. Biden expressed support for a price on carbon emissions during the primary, but Biden’s team has recently indicated he prefers a legislative approach centered on economic stimulus, clean energy investments, and sector-specific decarbonizations standards. Meanwhile, clean energy advocates are also pushing sector-specific decarbonization standards—such as a national standard for the power sector—instead of economy-wide carbon emissions fees.
Even with this shift in focus, the once-vaunted carbon-tax is not dead. Both House Democrats and Senate Democrats have independently released policy menus to tackle the climate crisis; each embraced a carbon tax to some degree. The House report specifically states that “Congress should establish a carbon pricing system designed to achieve America’s economy-wide greenhouse gas emissions reduction goal of net-zero by no later than 2050.” The Senate report endorses adopting market signals (like a carbon price) as part of a suite of policies to drive down emissions.
However, with the Senate nearly evenly split, a Biden Administration will likely need Republican support to enact “enforcement mechanism” legislation. Regardless of the ultimate composition of the Senate, former Energy Secretary Ernest Moniz (a Biden climate advisor) has argued that Republican support is necessary if the new administration wants to build a durable climate policy. Some Republicans have expressed support for carbon pricing and there are at least four carbon price bills with Republican co-sponsors. Most notably, the current Chair of the Senate Energy and Natural Resources Committee, Senator Lisa Murkowski (R-AK), has observed that a “price on carbon . . . should be one of the options that is on the table” if Congress takes up bipartisan climate legislation.
Apart from Republicans, industry has also inched towards supporting a carbon price. This year, the Business Roundtable endorsed the enactment of a “market-based emissions reduction strategy that includes a price on carbon,” though it did not signal support for any specific proposal. This fall, executives from J.P. Morgan Chase, Morgan Stanley, and BP all signed off on a Commodities Futures Trading Commissions report that calls for the United States to price carbon consistent with the Paris Climate Agreement. In another show of support, BP and Shell each pledged $1 million to Americans for Carbon Dividends, a group that lobbies for revenue-neutral carbon pricing. However, in exchange for a carbon fee, Americans for Carbon Dividends supports a repeal of the Environmental Protection Agency’s (EPA) regulatory authority over greenhouse gases, a position that may be politically unpalatable for Congressional Democrats.
President-elect Biden’s climate focus, the current composition of the Senate, and industry’s recent support, all indicate that a carbon price remains a viable policy in the corridors of Capitol Hill. Variations in current carbon pricing proposals in Congress suggest two key policy issues will need to be ironed out to move forward: (1) the subject and rate of taxation and (2) how it impacts EPA’s regulatory authority. In this post I discuss the fee structures of various proposals to date as well as how these proposals would affect EPA’s regulatory authority.
The Fee Itself
Economists broadly support carbon pricing; they consider greenhouse gas emissions to be a classic “market failure” that can be corrected with a tax. This tax would increase every year until emissions reductions targets are met and would ideally be set at a price that accurately reflects the costs of carbon emissions to society.
Recently, some economists have argued that policymakers should design a carbon price to align with specific decarbonization goals, instead of pricing carbon based on the social cost of emissions. Other economists have argued that climate modeling incorrectly focuses on pricing the damage caused by climate change. Instead, a carbon price should reflect the system-level risks caused by emissions. Under these risk-based models, a carbon fee takes the opposite shape of the “market-failure” models. It would start high, increase in the short-term, and then begin declining as the global risks posed by climate change decline.
While existing Congressional proposals vary widely, they all hue to the traditional “market failure” view by setting an initially low fee that increases over time to meet emission reduction targets. Assuming this would constitute the basis for a bipartisan “enforcement mechanism” bill, the most critical legislative questions will be what sources and greenhouse gases are taxed and at what rate this fee will be applied.
1. What is taxed?
A minority of the carbon fee bills pending in Congress apply only to carbon dioxide emissions specifically from the energy sector. Meanwhile, the remaining bills are better described as “greenhouse gas” taxes (not simply carbon fees) because they apply to all heat-trapping emission from any covered sources, including those outside the energy industry. Importantly, this broader coverage reaches methane, which has 80 times the heat-trapping power of carbon dioxide and makes up nearly 10% of all greenhouse gas emissions in the United States..
2. At what rate is the tax set?
Apart from varying with respect to the subject of taxation, congressional carbon fee proposals diverge significantly in their initial assessment amount and their subsequent increases. Each of the congressional proposals set an initial fee for the first year of taxation. This fee applies to each metric ton of carbon dioxide emissions (or carbon dioxide equivalent emissions for the broader greenhouse gas fees), as demonstrated in the following chart:
|Initial Fee Per Metric Ton||Yearly Increase||Additional Increase If Emissions Target Is Not Met?|
|H.R. 5457||Maloney||Just CO2||$40/metric ton||Inflation||No additional increase specified.|
|H.R. 4142||Larsen||Just CO2||$52/metric ton||Inflation||No additional increase specified.|
|H.R. 3966||Lipinski||Just CO2||$40/metric ton||Inflation||+ 2.5%|
|H.R. 4058||Rooney||CO2-eq||$30/metric ton||5% + inflation||+ $3 (only before 2031)|
|H.R. 4520||Fitzpatrick||CO2-eq||$35/metric ton||5% + inflation||+ $4 (only before 2031)|
|H.R. 763||Deutch/EICDA||CO2-eq||$15/metric ton||$10 + inflation||+ $5|
|H.R. 8175||McNerney||Just CO2||$25/metric ton||$10||No additional increase specified|
|S. 1128||Whitehouse||CO2-eq||$52/metric ton||Inflation||+ 6%|
|S. 2294||Coons||CO2-eq||$15/metric ton||$15||+ $15|
|S. 4484||Durbin||CO2-eq||$25/metric ton||$10 + inflation||+ $5 (2025-30); + $10 (2031-40); + $15 (2041+)|
For each subsequent year, the fees have a scheduled mandatory increase. If emissions reduction targets are not met, many of the proposals apply an additional increase for that year.
As an illustration for how this system could work, compare Sen. Coons’ proposals with Rep. Larsen’s bill. Under Sen. Coons’ bill the initial fee is set at $15/ton of CO2-eq emissions. The next year the fee would be $30/ton, unless the emissions reduction target was not met, in which case it would be $45/ton. While Sen. Coons’ proposals starts with the lowest initial fee, its sharp rate of increase means it could very well impose the most aggressive tax. On the other hand, Rep. Larsen begins with a seemingly aggressive $52/fee. However, Larsen’s bill would only adjust the fee for inflation; it would not mandate any real yearly increases, nor would it increase the assessed tax should carbon emissions continue to rise at an unsustainable rate.
3. Border Adjustment Mechanisms
Regardless of the subject and rate of taxation, all the carbon fee bills include some form of a border adjustment mechanism. Because a carbon tax could put manufacturers of carbon-intensive products at a disadvantage compared to their competitors in countries without a comparably stringent policy, these border adjustments require importers of carbon-intensive goods to pay a tax and providing a rebate to exporters of the same products. The Biden campaign has embraced a “carbon adjustment fee” to stop “polluting countries from undermining our workers and manufacturers,” indicating a Biden administration may support a border adjustment mechanism.
Repeal of Regulatory Authority under the Clean Air Act?
Many proponents of a carbon tax (in particular, prominent center-right thinkers like former Secretaries of State George Schultz and Jim Baker) argue that the EPA should be stripped of its authority to regulate greenhouse gases in exchange for enacting a carbon tax to reduce emissions. The logic is that a sufficiently aggressive tax would make additional regulation unnecessary and allow companies to reduce their emission in the most efficient method possible.
The most popular carbon fee proposal in Congress endorses this view. This bill, the Energy Innovation and Carbon Dividend Act (EICDA) of 2019, has 83 bipartisan co-sponsors and would suspend EPA’s ability to issue and enforce Clean Air Act regulations that “limit the emission of greenhouse gases from the combustion of” specified fossil fuels “on the basis of the emission’s greenhouse gas effects.” However, this repeal of regulatory authority would only apply to carbon emissions from stationary sources, such as power plants; EPA would retain authority to regulate methane emissions from power plants and oil & gas facilities. In effect, this means that EPA could not enact a new “Clean Power Plan” or “Affordable Clean Energy Rule” regulations put forward by the Obama and Trump administrations, respectively, to mitigate greenhouse gas emissions from the power sector.
Notably, EICDA would allow EPA to continue enacting greenhouse gas regulations for the transportation sector, which is the top source of U.S. carbon emissions. In particular, EPA would retain authority to set greenhouse gas standards for new passenger vehicles as well as light and heavy duty trucks. This type of vehicle emissions standard has been the subject of intense litigation during the Trump Administration and “developing new rigorous fuel economy standards” is a key part of Vice President Biden’s climate plan.
Additionally, under EICDA, EPA would retain authority to regulate airline emissions so long as such regulations are “not more stringent than the standards adopted by the International Civil Aviation Organization” (ICAO). The EPA has recently proposed limiting aircraft greenhouse emissions in line with the ICAO’s standards. However, both state attorneys general and environmental groups have critiqued the EPA’s proposal as insufficient. Under EICDA, EPA would not be able to adopt more stringent emissions limits for aircrafts until the ICAO updated its own standards.
Despite authorizing the repeal of some regulatory authority, EICDA does build in an important safeguard: if emissions reductions targets are not met by 2030, EPA regains its ability to regulate greenhouse gas emissions. This reinstatement of regulatory authority helps ensure that emissions decrease even if the carbon pricing mechanism proves ineffective. How easily greenhouse gas regulatory and enforcement programs could be reinstated in such circumstances remains an unanswered question.
While the 83 co-sponsors of EICDA, Schultz, and Baker all seem to agree on repealing at least some of EPA’s regulatory authority, many Congressional Democrats oppose such a measure. The House Democrat’s Climate Crisis Report explicitly states that “Congress should not offer liability relief or nullify Clean Air Act authorities or other existing statutory duties to cut pollution in exchange for a carbon price” and emphasizes that “Carbon pricing is not a silver bullet.” While the Senate Climate Crisis Report does not reject a repeal of EPA’s regulatory authority outright, it does conclude that a carbon price (acting alone) is unlikely to sufficiently reduce emissions. Accordingly, Senate Democrats recommend enacting “supporting policies like standards and regulatory requirements” to “ensure the intended outcome of net-zero emissions.” Additionally, none of the carbon price bills proposed by Democratic Senators endorse a repeal of EPA’s regulatory authority. Given these proposals, the majority of Congressional Democrats would likely oppose any efforts to repeal EPA’s regulatory in exchange for the enactment of a carbon fee. This disagreement on whether to repeal EPA’s existing regulatory authority could become the primary impediment to bipartisan Congressional action.
Politics: The Ultimate Decider
The ultimate test of whether a carbon “enforcement mechanism” will be enacted (and what shape it will take) depends on the dynamics in the Senate and the broader political climate. The history of Congressional efforts to enact carbon pricing leaves plenty of room for pessimism. Even when Democrats controlled both the House and the Senate, President Obama’s efforts to pass a cap-and-trade bill were ultimately defeated by the failure to reach bipartisan agreement. In Washington (a state that has thrice elected noted climate-leader Jay Inslee as Governor) efforts to pass a carbon tax failed in both 2016 and 2018.
Most importantly, if Democrats fail to take control of the Senate this January, the fate of all legislation will depend on the graces of current Senate Majority Leader Mitch McConnell, who represents many coal mining communities in Kentucky and has historically opposed climate-related measures. President-elect Biden’s ability to push forward climate legislation may depend on how well his touted deal-making abilities can forge legislative action in this difficult political environment.
 CNN, Climate Crisis Town Hall with Joe Biden (D), Presidential Candidate (Aired September 4, 2019 – 20:00 ET) (COOPER: Would you support a carbon tax? Some other candidates say they would. BIDEN: Yeah, no, I would.”) http://transcripts.cnn.com/TRANSCRIPTS/1909/04/se.05.html.
 See Amy Harder, Joe Biden unlikely to push carbon tax as part of climate change plan, Axios (Aug. 20, 2020) (“The [climate] community has largely moved into a different framework,” said John Podesta, a longtime Democratic political operative who has advised the last two Democratic presidents. “A real disadvantage of just a pricing scheme is you can’t directly attack the environmental injustice problem,” said Podesta, who is in regular contact with the Biden campaign. “In contrast, Biden has proposed that 40% of the [clean energy] investments go to distressed communities.”) https://www.axios.com/joe-biden-carbon-tax-climate-change-plan-e8d522a8-5015-45fc-8164-3ec5c8a0d8a3.html; see also Biden For President, The Biden Plan To Build A Modern, Sustainable Infrastructure And An Equitable Clean Energy Future (Announcing that Biden will seek to make a $2 Trillion investment in clean energy technology and “move ambitiously to generate clean, American-made electricity to achieve a carbon pollution-free power sector by 2035”) https://joebiden.com/clean-energy/.
 Dave Roberts, At last, a climate policy platform that can unite the left, VOX (July 9, 2020) (Noting that carbon taxes never saw the bipartisan support their backers always promised and that the political left is unifying around decarbonization approach focused on sector-specific standards) https://www.vox.com/energy-and-environment/21252892/climate-change-democrats-joe-biden-renewable-energy-unions-environmental-justice; Leah C. Stokes & Matto Mildenberger, Trouble With Carbon Pricing, Boston Policy Review (Sept. 24, 2020) (rejecting a carbon price as politically infeasible and favoring an approach centered on “standards, investments, and justice”) (http://bostonreview.net/science-nature-politics/matto-mildenberger-leah-c-stokes-trouble-carbon-pricing.
 House Select Committee on the Climate Crisis, Solving the Climate Crisis: The Congressional Action Plan for a Clean Energy Economy and a Healthy, Resilient, and Just America at 286 (June 2020) [hereinafter House Climate Report] https://climatecrisis.house.gov/sites/climatecrisis.house.gov/files/Climate%20Crisis%20Action%20Plan.pdf.
 Senate Democrat’s Special Committee on the Climate Crisis, The Case for Climate Action: Building a Clean Economy for the American People, at 38 (Aug. 25, 2020) (“a carbon price—if implemented alone—would need to be quite high to drive deep emission reductions. Supporting policies like standards and regulatory requirements, when implemented with a reasonable carbon price, can help ensure the intended outcome of net-zero emissions.”)[ hereinafter Senate Climate Report] https://www.schatz.senate.gov/imo/media/doc/SCCC_Climate_Crisis_Report.pdf
 Paul Kane, Control of the Senate heads into overtime as Georgia braces for runoff elections, Washington Post (Nov. 5, 2020) https://www.washingtonpost.com/politics/senate-georgia-election-trump/2020/11/05/8d491038-1f7f-11eb-90dd-abd0f7086a91_story.html.
 Juliet Eilperin & Annie Linskey, How Biden aims to amp up the government’s fight against climate change, Washington Post (Nov. 11, 2020) (“Ernest Moniz, Obama’s former energy secretary, said legislation passed with support from both parties tends to be the best way to make durable change — and that it is still worth trying. ‘My view of reality is that it’s very, very hard to get major systemic change in this country without some considerable degree of bipartisan support,’ Moniz said.”)
 See Resources for the Future, Carbon Pricing Bill Tracker (Oct 1. 2020) (showing four bills in the 116th Congress with Republican co-sponsors) https://www.rff.org/publications/data-tools/carbon-pricing-bill-tracker/.
 Stanford | Institute for Economic Policy Research, Prospects for Significant Bipartisan Climate-Change Legislation In the Next U.S. Congress: A Conversation with Senators Lisa Murkowski and Sheldon Whitehouse (October 21, 2020) (at 23:00) (When asked about the prospects of bi-partisan climate legislation, Senator Murkowski (R-AK) said, “. . . as I’m talking to the folks Senator Whitehouse was just mentioning, those in the corporate sector, they’re looking more and more to give us, give us some certainty with a price signal and I know that a price on carbon is one that makes Republicans more than a little bit nervous but I do think that that can be and that should be one of the options that is one the table for discussion in terms of how you can move policies forward.” ) https://siepr.stanford.edu/events/prospects-significant-bipartisan-climate-change-legislation-next-us-congress-conversation?fbclid=IwAR0iLhxvqg3_RBvwMGcF6P37s_hhccbrF30qfbVQZN3nR_TO_rcgmsT-1PE.
 See Eric Roston & Benjamin Bain, JPMorgan, Morgan Stanley Join Call for U.S. Carbon Pricing, Bloomberg Green (Sept. 9, 2020) https://www.bloomberg.com/news/articles/2020-09-09/jpmorgan-morgan-stanley-bp-join-call-for-u-s-carbon-pricing.
 Amy Harder, The big corporate shift on climate change, Axios https://www.axios.com/the-big-corporate-shift-on-climate-change-1edea61e-ca43-4df9-a293-d42e00f08caa.html.
 See Americans for Carbon Dividends, 4 Steps To Solving Climate Change (“The third pillar is the streamlining of regulations that are no longer necessary upon the enactment of a rising carbon fee. In the majority of cases where a carbon fee offers a more cost-effective solution, the fee will replace regulations. All current and future federal stationary source carbon regulations, for example, would be displaced or preempted.”) https://www.afcd.org/the-four-pillars/.
 The House Climate Report explicitly rejects this policy. House Climate Report at 286 (“Congress should not offer liability relief or nullify Clean Air Act authorities or other existing statutory duties to cut pollution in exchange for a carbon price”).
 See, e.g., William D. Nordhaus, Rolling the “Dice”: An Optimal Transition Path for Controlling Greenhouse Gases, Cowles Foundation for Research in Economics at Yale University (June 1992) (arguing that a modest carbon tax would yield more in climate benefits than it would cost, should start at a modest level, and rise over time) http://cowles.yale.edu/sites/default/files/files/pub/d10/d1019.pdf; see also Economists Statement on Carbon Dividends, Wall Street Journal (Jan. 16, 2019) https://www.wsj.com/articles/economists-statement-on-carbon-dividends-11547682910.
 See, e.g., Pigou, A. C., The Economics of Welfare (Macmillan, 1932).
 See Kaufman, N., Barron, A.R., Krawczyk, W. et al. A near-term to net zero alternative to the social cost of carbon for setting carbon prices. Nat. Clim. Chang. 10, 1010–1014 (2020). https://doi.org/10.1038/s41558-020-0880-3.
 See Kent D. Daniel, Robert B. Litterman, and Gernot Wagner, Declining CO2 Price Paths, PNAS October 15, 2019 116 (42) 20886-20891; first published October 1, 2019; https://doi.org/10.1073/pnas.1817444116.
 Three proposals assess fees specifically on each metric ton of carbon dioxide emissions (as opposed to all greenhouse gases) emitted by coal, petroleum, and natural gas production. .R. 3966 (Imposing fee for “carbon dioxide emission potential” of coal, petroleum products and natural gas); H.R. 5457 (“In the case of a coal mine or an oil or gas well, there is hereby imposed a tax equal to $40 per ton of carbon contained in fuel produced”); H.R. 4142 (taxing “applicable amount per ton of carbon dioxide content of such substance on coal, petroleum/any petroleum product, and natural gas”). The remaining five bills tax greenhouse gases apart from carbon dioxide. For instance, Sen Whitehouse’s bill requires an assessment of the “associated emissions” attributable to venting, flaring, and leakage in order to account for “methane and other greenhouse gases” emitted across the supply chains of coal, natural gas, and petroleum products. S. 1128, §4694. These associated emissions are then taxed at their carbon dioxide equivalent rate (CO2-eq). Id. Meanwhile, the remaining four bills all apply a single fee for the CO2-eq of the total greenhouse gas emissions from coal, petroleum, and natural gas production. See H.R. 763; S.2284; H.R. 4520; H.R. 4508. Unlike Sen. Whitehouse’s bill, which first imposes a fee for CO2 emissions and then imposes an additional fee for associated emissions, these four proposals apply one fee for the total greenhouse gas content of the covered fuel. See, e.g., S. 2284, § 4692 (“(b) AMOUNT OF THE CARBON FEE.—The carbon fee imposed by this section is an amount equal to— (1) the greenhouse gas content of the covered fuel, multiplied by (2) the carbon fee rate.”)
 See Coral Davenport, E.P.A. to Lift Obama-Era Controls on Methane, a Potent Greenhouse Gas, New York Times (August 10, 2020) https://www.nytimes.com/2020/08/10/climate/trump-methane-climate-change.html.
 The bills vary in their annual targets. For instance, both the Whitehouse and Lipinski bills specify that annual emissions reduction targets are not met in any year where greenhouse gas emissions exceed 20% of 2005 emission levels. S. 1128; H.R. 3966 Meanwhile, both the Coons bill and EICDA provide a schedule of yearly emissions reduction targets designed to reach net-zero emissions by 2050. The Coons bill provides a ten-year schedule aiming for 45% of 2017 emissions by 2030. Thereafter, it requires annual decreases of 2.5% from 2017 emissions levels until reaching net-zero emissions in 2050 S. 2284, § 4693. Meanwhile, EICDA sets the following targets: 2020-2024: No emissions reduction target; 2025-2034: 5% reduction from 2016 emissions per year; 2035-2050: 2.5% reduction from 2016 emissions per year. .H. R. 763. Finally, both Rooney and Fitzpatrick set annual targets for each year based on the cumulative amount of carbon dioxide equivalent emissions, measured from the beginning of 2021. For instance, if at the end of 2021, total emissions are 5,000 million metric tons of carbon dioxide equivalent emissions, the emissions target has been met. However, at the end of the next year, the annual target will be met if cumulative emissions for the past two years are 9,800 million metric tons of carbon dioxide equivalent emissions. These cumulative emission targets are set through 2031, when the target for the preceding 10 years is 49,700 million metric tons of carbon dioxide equivalent emissions. H.R. 4058; H.R. 4520.
 For example, EICDA and Sen. Coons’ bill create similar statutory processes for setting border adjustments for fuels and carbon-intensive products. For imported fuels and carbon intensive products, these bills impose a fee equal to the difference between the domestic and foreign cost of carbon. See H.R. 763, §9908 (imposing fee on imported covered fuels for the full fuel cycle GHG emissions of such fuels over the total foreign cost of carbon carried by such fuel and imposes fee on carbon-intensive products on the production greenhouse gas emission so much products over the total foreign cost of carbon carried for that product); see also S. 2284, § 4696 (imposing fee on imports equal to equal to amount of full fuel cycle GHG emissions of such fuel times the ratio of the domestic carbon fee rate over the foreign carbon fee rate). For exported fuels and carbon intensive products, these bills provide a refund to offset any differences in the domestic and foreign costs of carbon. See H.R. 763, §9908; see also S. 2284, § 4696. Both proposals allow the Treasury Secretary to designate products as “carbon intensive” while also providing an initial list of covered products, such as iron, steel, cement, aluminum, and glass. S. 2284 § 4691; H.R. 734.
 Jason Bordoff & Noah Kaufman, A Federal U.S. Carbon Tax: Major Decisions and Implications, Joule (December 19, 2018) https://www.energypolicy.columbia.edu/sites/default/files/pictures/A%20FederalUSCarbon.pdf
 Climate Leaders Council, The Conservative Case For Carbon Dividends (“The final pillar is the elimination of regulations that are no longer necessary upon the enactment of a rising carbon tax whose longevity is secured by the popularity of dividends. Much of the EPA’s regulatory authority over carbon dioxide emissions would be phased out, including an outright repeal of the Clean Power Plan. Robust carbon taxes would also make possible an end to federal and state tort liability for emitters. To build and sustain a bipartisan consensus for regulatory simplification of this magnitude, the initial carbon tax rate should be set to exceed the emissions reductions of current regulations.”) https://www.clcouncil.org/media/2017/03/The-Conservative-Case-for-Carbon-Dividends.pdf.
 Id. (“because many regulations would become unnecessary, the plan would give companies the flexibility to reduce emissions in the most efficient way.”)
 H.R.763 – Energy Innovation and Carbon Dividend Act of 2019, Congress.Gov https://www.congress.gov/bill/116th-congress/house-bill/763/cosponsors.
 See H.R. 763, § 8(a).
 See, e.g., H.R. 763, § 8(a).
 The language in several bills provides that “nothing in this section limits the Administrator’s authority to regulate greenhouse gas emissions from . . . facilities that . . . are subject to subpart OOOO or OOOOa of part 60 of title 40, Code of Federal Regulations.” H.R. 763 § 8(a). These subparts cover EPA regulation of methane and volatile organic compound emissions from both existing and new oil and natural gas facilities. See 40 CFR § 60.5360a.
 For information on these rules, see EELP Staff, Clean Power Plan / Carbon Pollution Emission Guidelines, Environmental & Energy Law Program https://eelp.law.harvard.edu/2017/09/clean-power-plan-carbon-pollution-emission-guidelines/.
 Transportation Replaces Power in U.S. as Top Source of CO2 Emissions, Yale Environment 360 (December 4, 2017) https://e360.yale.edu/digest/transportation-replaces-power-in-u-s-as-top-source-of-co2-emissions
 See, e.g., EELP Staff, Heavy-duty Truck “Glider Kit” Rule, Environmental and Energy Law Program, https://eelp.law.harvard.edu/2018/02/heavy-duty-truck-glider-kit-rule/ (last visited June 25, 2020); Corporate Average Fuel Economy Standards & Greenhouse Gas Standards for Passenger Cars and Light Duty Trucks, Environmental and Energy Law Program, http://eelp.law.harvard.edu/wp-content/uploads/EELP-Car-Rules-Backgrounder-Final.pdf (last visited June 25, 2020).
 See, e.g., EELP Staff, Corporate Average Fuel Economy Standards / Greenhouse Gas Standards, Environmental and Energy Law Program https://eelp.law.harvard.edu/2017/09/corporate-average-fuel-economy-standards-greenhouse-gas-standards/ ; see also Coral Davenport, U.S. to Announce Rollback of Auto Pollution Rules, a Key Effort to Fight for Climate Change, New York Times (March 30, 2020) https://www.nytimes.com/2020/03/30/climate/trump-fuel-economy.html.
 Biden for President, The Biden Plan for a Clean Energy Revolution and Environmental Justice, https://joebiden.com/climate-plan/ (“Reducing greenhouse gas emissions from transportation – the fastest growing source of U.S. climate pollution – by preserving and implementing the existing Clean Air Act, and developing rigorous new fuel economy standards aimed at ensuring 100% of new sales for light- and medium-duty vehicles will be electrified and annual improvements for heavy duty vehicles.”)
 H.R. 763 §§ 8(e)-(d).
 Control of Air Pollution From Airplanes and Airplane Engines: GHG Emission Standards and Test Procedures, 85 Fed. Reg. 51556 (Aug. 20, 2020).
 See, e.g. Environmental Defense Fund et al., Comment to Proposed Rule on Control of Air Pollution From Airplanes and Airplane Engines: GHG Emission Standards and Test Procedures (Oct. 19, 2020) (“EPA’s proposal would finalize standards that have no effect on emissions and require no technological improvements; instead, it would adopt as a matter of domestic U.S. regulations international standards that themselves are a decade behind what the industry will achieve absent any regulatory effort.”); California et al., Comment to Comment to Proposed Rule on Control of Air Pollution From Airplanes and Airplane Engines: GHG Emission Standards and Test Procedures (Oct. 19, 2020) (“The substantive standards that EPA proposes to adopt—the 2016 GHG standards developed by the International Civil Aviation Organization (ICAO)—lag existing technology by more than 10 years and would result in no GHG reductions at all compared to business-as-usual. In fact, EPA has not even considered any form of emission control that would reduce GHGs, despite the agency’s determination that these emissions endanger public health and welfare.”).
 H.R. 763 § 8(a).
 House Climate Report at 286.
 Senate Climate Report at 38.
 See, e.g., Stephen Power, Senate Halts Effort to Cap CO2 Emissions, Wall Street Journal (July 23, 2010) https://www.wsj.com/articles/SB10001424052748703467304575383373600358634; Ryan Lizza, As the World Burns, The New Yorker (October 3, 2010) https://www.newyorker.com/magazine/2010/10/11/as-the-world-burns.
 David Roberts, Washington votes no on a carbon tax – again, Vox (Nov. 6, 2018) https://www.vox.com/energy-and-environment/2018/9/28/17899804/washington-1631-results-carbon-fee-green-new-deal.
 James Bruggers, Senate 2020: Mitch McConnell Now Admits Human-Caused Global Warming Exists. But He Doesn’t Have a Climate Plan, Inside Climate News (Sept. 9, 2020) https://insideclimatenews.org/news/03092020/kentucky-2020-senate-climate-change-election-mitch-mcconnell-amy-mcgrath.
 Janet Hook, Biden the dealmaker: Can his approach work in a polarized post-Trump America?, Los Angeles Times (Aug. 16, 2020) https://www.latimes.com/politics/story/2020-08-16/biden-bipartisan-deals-possible-anymore.