U.S. Greenhouse Gas Emissions Trends and Projections from the Inflation Reduction Act

U.S. Greenhouse Gas Emissions Trends and Projections from the Inflation Reduction Act

U.S. Greenhouse Gas Emissions Trends and
January 12, 2023
Projections from the Inflation Reduction Act
Jonathan L. Ramseur
Pursuant to international climate change treaty obligations, the United States submitted a
Specialist in Environmental
nonbinding pledge in 2021 to reduce its greenhouse gas (GHG) emissions by 50%-52% below
Policy
2005 levels by 2030. The 117th Congress enacted several laws that, in part, support this GHG

emissions reduction target: the Infrastructure Investment and Jobs Act (IIJA; P.L. 117-58) and a
budget reconciliation measure commonly referred to as the Inflation Reduction Act of 2022

(IRA; P.L. 117-169). IRA, in particular, represents a milestone in U.S. federal climate policy.
Each of the eight IRA titles contains some number of provisions that directly or indirectly address U.S. GHG emissions.
Members of Congress may consider IRA and IIJA and the GHG emissions goals within a wider context, including recent
GHG emissions trends and the role of existing federal and state climate policies. In addition, Congress may consider whether
the new laws are sufficient to meet U.S. emissions reduction commitments and how the recently enacted provisions may
interact with any proposed laws or regulations. Some Members have voiced opposition to IRA provisions, which may affect
the oversight of its implementation in the 118th Congress.
U.S. GHG emissions reached their highest level in 2007 and have generally decreased since that time. The 2020 annual
emission levels were approximately 21% below levels in 2005—the year the United States uses as a benchmark for its
international GHG pledges. The decrease in emissions between 2019 and 2020 was largely due to the impacts of the
Coronavirus Disease 2019 (COVID-19) pandemic on travel and economic activity. Based on carbon dioxide (CO2) emissions
data, total U.S. GHG emissions likely increased between 2020 and 2021.
Federal climate change policies have evolved and currently include a range of activities implemented under various legal
authorities. Federal rulemakings that address GHG emissions have generated considerable interest, controversy, and court
challenges. In some cases, the rulemakings are still under development and have not been implemented.
Several recent analyses use computer simulation models to prepare estimates of U.S. GHG emissions through 2030. These
models compare baseline scenarios with emission scenarios that include the effects of legislation enacted in the 117th
Congress, particularly IRA. The models indicate that under baseline conditions (i.e., without IRA), U.S. GHG emissions
would decrease by 24% to 35% by 2030 compared with 2005 levels. The models estimate that with the addition of IRA, U.S.
GHG emissions would decrease by 30% to 43% by 2030 compared with 2005 levels. The range of estimates is due to a
number of uncertain factors, such as future oil and natural gas prices, the rate of increase in electricity transmission, and
implementation of IRA provisions, among others.
None of the modeled scenarios indicates that the United States would meet its 2030 GHG emissions target. Some of the non-
modeled provisions may promote the development of technologies that could result in emissions reductions over a longer
time horizon. In addition, the estimates indicate that most of IRA’s projected emissions reductions come from the electric
power sector in the 2030 time frame, and other provisions—particularly those affecting emissions in the transportation
sector—are expected to result in emissions reductions after 2030.
If Members want to spur U.S. GHG emissions reduction beyond the projections from the models, a range of policy options
remain available. Policymakers could increase IRA’s funding amounts or tax incentives. Alternatively, policymakers could
employ different approaches in subsequent legislation. Options include market-based approaches, such as carbon pricing
mechanisms or regulatory standards for particular facilities or sectors. To some degree, such efforts are underway at the state
level. In addition, a range of developing federal regulatory actions would likely play a role in the level of U.S. emissions over
time. The authors of the modeling studies point out that the IRA climate provisions would decrease costs associated with
other existing or future requirements or policy activity from the federal government or state and local governments. If these
additional policies were implemented, some argue, they may help achieve the 2030 target.
Congressional Research Service

link to page 4 link to page 5 link to page 7 link to page 8 link to page 10 link to page 11 link to page 11 link to page 12 link to page 12 link to page 13 link to page 14 link to page 15 link to page 18 link to page 6 link to page 7 link to page 15 link to page 16 link to page 17 link to page 19 U.S. Greenhouse Gas Emissions Trends and Projections from the Inflation Reduction Act

Contents
Introduction ..................................................................................................................................... 1
Historical U.S. GHG Emissions and Recent Trends ....................................................................... 2
U.S. Climate Change Policies—In Brief ......................................................................................... 4
Federal Policies ......................................................................................................................... 5
State and Local Policies ............................................................................................................ 7
Climate Change Legislation ............................................................................................................ 8
Legislative Approaches Prior to the 117th Congress .................................................................. 8
Climate Change Legislation in the 117th Congress ................................................................... 9
Infrastructure Investment and Jobs Act ............................................................................... 9
Inflation Reduction Act ..................................................................................................... 10
U.S. GHG Emission Reduction Goals ............................................................................................ 11
U.S. GHG Emission Estimates in 2030 ......................................................................................... 12
Considerations for the 118th Congress ........................................................................................... 15

Figures
Figure 1. Total Gross U.S. GHG Emissions and Emissions by Sector: 1990-2020 ........................ 3
Figure 2. Percentage of Total Electricity Generation by Energy Source ......................................... 4
Figure 3. Historical U.S. GHG Net Emissions Compared with U.S. Emissions Targets .............. 12
Figure 4. Net U.S. GHG Emissions, Selected Emission Estimates, and U.S. NDC ...................... 13
Figure 5. Estimated GHG Emissions Reductions by Sector in 2030 ............................................ 14

Contacts
Author Information ........................................................................................................................ 16

Congressional Research Service

U.S. Greenhouse Gas Emissions Trends and Projections from the Inflation Reduction Act

Introduction
Millions of discrete sources throughout the United States produce greenhouse gas (GHG)
emissions.1 These sources include motor vehicles, electric power plants, industrial facilities,
commercial buildings, households, and agricultural activities. Human-related GHG emissions
have increased since the beginning of the industrial era, increasing atmospheric concentrations of
GHGs.2
A wide array of actions that seek to reduce GHG emissions are underway or being developed by
international and subnational entities (e.g., U.S. state actions or regional partnerships), as well as
by the U.S. federal government. Federal climate change policies have evolved and currently
include a range of activities implemented under various legal authorities, such as the Clean Air
Act.
The 117th Congress considered and ultimately enacted two laws that include a number of
provisions that could have direct or indirect effects on U.S. GHG emission levels.
 On November 15, 2021, President Biden signed the Infrastructure Investment and
Jobs Act (IIJA; P.L. 117-58). IIJA is a broad infrastructure law that addressees
multiple economic sectors that produce GHG emissions, including transportation
and energy, among others.
 On August 16, 2022, President Biden signed a budget reconciliation measure
commonly referred to as the Inflation Reduction Act of 2022 (IRA; P.L. 117-
169). Each of the eight IRA titles contains some number of provisions that
directly or indirectly address issues related to climate change, including reduction
of U.S. GHG emissions.
Several organizations, including the Department of Energy, have used models to assess the effects
these acts may have on U.S. GHG emission levels over the next decade.3 This report examines
these assessments and considers their results in a wider context. For example, how do the
projected emissions reductions compare with historical emissions levels and recent trends? How

1 The primary greenhouse gases (GHGs) emitted by human activities—and estimated by the U.S. Environmental
Protection Agency (EPA) in its annual inventories—include carbon dioxide (CO2), methane, nitrous oxide, sulfur
hexafluoride, chlorofluorocarbons, hydrofluorocarbons, and perfluorocarbons. Other GHGs include water vapor,
carbonaceous and sulfuric aerosols, hydrochlorofluorocarbons, and elevated tropospheric ozone pollution generated by
emissions of nitrogen oxides and volatile organic compounds, such as solvents.
2 For example, atmospheric concentrations of CO2 have increased by over 45% compared with preindustrial levels (i.e.,
1850-1990). See Intergovernmental Panel on Climate Change (IPCC), AR6 Climate Change 2021: The Physical
Science Basis, August 9, 2021, p. SPM-5, at https://www.ipcc.ch/report/ar6/wg1/.
3 The modeling groups include the following: Rhodium Group, A Turning Point for US Climate Progress: Assessing
the Climate and Clean Energy Provisions in the Inflation Reduction Act, August 12, 2022, at https://rhg.com/research/
climate-clean-energy-inflation-reduction-act/ (hereinafter Rhodium Group, A Turning Point for US Climate Progress);
Princeton University Rapid Energy Policy Evaluation and Analysis Toolkit (REPEAT), Electricity Transmission is Key
to Unlock the Full Potential of the Inflation Reduction Act, September 2022, at https://repeatproject.org/docs/
REPEAT_IRA_Transmission_2022-09-22.pdf (hereinafter Princeton REPEAT, Electricity Transmission); Princeton
University REPEAT, Preliminary Report: The Climate and Energy Impacts of the Inflation Reduction Act of 2022,
August 2022, at https://repeatproject.org/docs/REPEAT_IRA_Prelminary_Report_2022-09-21.pdf (hereinafter
Princeton REPEAT, Preliminary Report); Energy Innovation, Modeling the Inflation Reduction Act Using the Energy
Policy Simulator, August 23, 2022, at https://energyinnovation.org/publication/modeling-the-inflation-reduction-act-
using-the-energy-policy-simulator/ (hereinafter Energy Innovation, Modeling the Inflation Reduction Act); and
Department of Energy, “The Inflation Reduction Act Drives Significant Emissions Reductions and Positions America
to Reach Our Climate Goals,” August 2022, at https://www.energy.gov/sites/default/files/2022-08/
8.18%20InflationReductionAct_Factsheet_Final.pdf.
Congressional Research Service

1

link to page 6 U.S. Greenhouse Gas Emissions Trends and Projections from the Inflation Reduction Act

do the projected reductions compare with hypothetical scenarios without the recent enactments of
IIJA and IRA (i.e., baseline scenarios)? How do the projected reductions compare with U.S.
emission reduction goals for 2030?
A discussion of these issues provides further context for the potential role that these acts may play
in U.S. climate policy going forward. Policymakers may consider whether the existing policies
are sufficient to meet specific objectives. Another consideration for Members is how these
recently enacted policies may interact with any subsequent laws or regulations.
This report
 discusses historical U.S. GHG emissions and trends;
 highlights federal and state climate change policies, particularly those addressing
GHG emission levels, but does not provide a comprehensive summary of all
policies related to climate change;
 briefly discusses the history of federal climate change legislation and summarizes
two enacted measures in the 117th Congress, IIJA and IRA;
 discusses U.S. goals to reduce GHG emissions by 2030 and beyond;
 discusses recent estimates of U.S. GHG emissions for 2030, particularly
regarding the potential emission effects from IRA; and
 provides considerations for policymakers in the context of the emissions
projections.
Historical U.S. GHG Emissions and Recent Trends
The U.S. Environmental Protection Agency (EPA) prepares an annual inventory of U.S. GHG
emissions. The inventory includes estimates of gross emissions, emission sinks, and net
emissions.4 The most recent inventory includes annual estimates from 1990 through 2020.5 As
illustrated in Figure 1, gross U.S. GHG emissions reached their highest level in 2007 and
generally decreased since that time. The 2020 annual emission levels were approximately 20%
below levels in 2005—the year the United States uses as a benchmark for its international GHG
pledges.
Policymakers may view the 2020 emission levels and their relationship with U.S. goals with some
caution. The 9% decrease in emissions between 2019 and 2020 was the largest annual decline in
EPA’s inventory history and, according to EPA, “largely due to the impacts of the coronavirus
(COVID-19) pandemic on travel and economic activity.”6 Carbon dioxide (CO2) emissions data
from the energy sector for 2021 appear to indicate that total U.S. GHG emissions likely increased

4 Gross emissions refer to total emissions from all sources, and it does not account for removals of CO2 emissions from
the atmosphere by emission sinks, such as forests, vegetation, and soils. U.S. sinks removed about 812 million metric
tons (MMT) in 2020, about 14% of gross emissions. Net emissions include the sum of gross emissions estimates and
removal estimates. The U.S. Nationally Determined Contribution (NDC) is measured in terms of net emissions. EPA,
Inventory of U.S. Greenhouse Gas Emissions and Sinks, 2022, at https://www.epa.gov/ghgemissions/inventory-us-
greenhouse-gas-emissions-and-sinks-1990-2020 (hereinafter EPA GHG Inventory).
5 GHG emissions data and trends can be presented in several ways, with each presentation telling a different story. The
GHG emissions in EPA’s GHG Inventory and in this report generally concern annual emission levels. Other GHG
emission measures include cumulative GHG emissions, GHG emissions intensities (e.g., emissions per gross domestic
product), and GHG emissions per capita.
6 EPA GHG Inventory, p. ES-4.
Congressional Research Service

2

link to page 6
U.S. Greenhouse Gas Emissions Trends and Projections from the Inflation Reduction Act

between 2020 and 2021. The Energy Information Administration (EIA) provides energy-related
CO2 emissions on a more up-to-date schedule than EPA’s inventory, which involves an
interagency process as well as expert and public reviews before finalization.7 EIA found that CO2
emissions account for approximately 80% of total U.S. GHG emissions, and their fluctuations
generally track with the annual percentage changes in total GHG emissions from EPA’s
inventories.8 EIA data indicate that CO2 emissions from the energy sector increased by 7%
between 2020 and 2021.9 Total GHG emissions are likely to follow a similar trend in 2021.
Figure 1 shows the GHG emissions contributions and trends by sector between 1990 and 2020.
As the figure indicates, emissions in the electricity sector decreased by 40% between 2005 and
2020. As the side-by-side comparison illustrates, the decrease in total U.S. GHG emissions over
the past 15 years is related to decreases in the electricity sector.
Figure 1. Total Gross U.S. GHG Emissions and Emissions by Sector: 1990-2020

Source: Prepared by the Congressional Research Service (CRS) using data from the U.S. Environmental
Protection Agency (EPA), Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2020, 2022, at
https://www.epa.gov/ghgemissions/inventory-us-greenhouse-gas-emissions-and-sinks (EPA GHG Inventory).
Notes: MMTCO2e = mil ion metric tons of carbon dioxide-equivalent emissions. MMTCO2e is used because
greenhouse gases (GHGs) vary by global warming potential (GWP). GWP is an index that allows comparisons of
the heat-trapping ability of different gases over a period of time. The scales of the y-axes in the above figures are
different. The figure presents gross emissions (i.e., the total emissions from all sources), and it does not account
for net removals of carbon dioxide (CO2) emissions from the atmosphere by vegetation and other sinks. U.S.

7 Although the EPA and Energy Information Administration (EIA) estimates are generally consistent, there are minor
differences in how some emissions are reported.
8 Based on a comparison of the annual rates of change between CO2 emissions in the energy sector (EIA data) and total
GHG emissions (EPA data).
9 Emission levels in 2021 were 3% below levels in 2019. See EIA, Monthly Energy Review, September 2022, at
https://www.eia.gov/totalenergy/data/monthly/#environment.
Congressional Research Service

3

link to page 7
U.S. Greenhouse Gas Emissions Trends and Projections from the Inflation Reduction Act

GHG emissions can be categorized in a variety of ways. This figure uses the economic sectors from EPA’s GHG
Inventory.
Developments in the U.S. electricity generation portfolio played a key role in the emissions
decrease in the electricity sector and total U.S. emission levels. Different fossil fuels, such as coal
and natural gas, generate different amounts of GHGs per unit of generated electricity. For
example, a typical natural-gas unit in the United States yields about 40% of the GHG emissions
of a coal-fired unit per megawatt-hour of electricity.10 Some sources of electricity generation,
such as nuclear power, wind, and solar, emit no GHG emissions at the point of power generation.
As illustrated in Figure 2, over the past decade, coal’s contribution to electricity generation
decreased, while natural gas and renewable generation both increased. Several factors likely
played a role in this change, including technological advances, particularly hydraulic fracturing,
as well as federal tax incentives for renewable energy and renewable portfolio standards in the
states.11
Figure 2. Percentage of Total Electricity Generation by Energy Source
2005-2021

Source: Prepared by CRS using data from Energy Information Administration (EIA), “Electric Power Monthly,”
Table 1.1, at https://www.eia.gov/totalenergy/data/monthly/#environment.
Notes: Renewable sources include wind, utility scale solar, wood fuels, landfil gas, biogenic municipal solid
waste, other biomass, and geothermal. Petroleum includes petroleum liquids and petroleum coke.
U.S. Climate Change Policies—In Brief
Historically, policymaking entities in the United States—Congress, federal agencies, state and
local governments—have proposed, and in some cases established, a variety of climate change

10 See EIA, “How Much Carbon Dioxide Is Produced per Kilowatthour When Generating Electricity with Fossil
Fuels,” at https://www.eia.gov/tools/faqs/faq.cfm?id=74&t=11.
11 For more discussion, see CRS Report R45453, U.S. Carbon Dioxide Emissions in the Electricity Sector: Factors,
Trends, and Projections, by Jonathan L. Ramseur.
Congressional Research Service

4

U.S. Greenhouse Gas Emissions Trends and Projections from the Inflation Reduction Act

policy approaches. In many cases, the policy approaches have generated considerable debate and
opposition from policymakers and stakeholders.
The following sections highlight developments and activities at the federal, state, and local
government levels. These policies have played varying roles in the recent trends in GHG
emissions levels and they will continue to affect levels going forward.
Federal Policies12
A variety of federal policies have indirectly affected GHG emissions through the years. These
have involved a range of activities implemented under various legal authorities. These activities
have included regulatory standards, tax incentives, data gathering and reporting, and financial
support for GHG mitigation technologies. Several of these regulatory programs continue today
and have indirectly limited GHG emission increases from vehicles,13 appliances and equipment,
buildings,14 and transportation fuels.15
A 2007 Supreme Court decision altered the federal environmental policy landscape. In
Massachusetts v. EPA, the Court ruled that EPA has authority under the Clean Air Act to regulate
GHG emissions from motor vehicles as air pollutants. This decision led to a shift in federal
policies toward more direct regulation of GHG emissions. During the Obama Administration,
EPA issued rules to limit GHGs from various sources, including electric power plants, vehicles,
and oil and natural gas production facilities. These rulemakings, and related efforts that followed,
have generated considerable interest, controversy, and court challenges.16 In some cases, the
rulemakings are still under development and have not been implemented. Other rules remain in
place.17
Executive branch policies and actions addressing U.S. GHG emissions typically reflect the policy
objectives of the incumbent Administration at the time. Recent EPA regulatory activities include,
but are not limited to, the following:

12 For more details regarding the history of federal climate change policies, see CRS Report R46947, U.S. Climate
Change Policy, coordinated by Richard K. Lattanzio.
13 For example, the Corporate Average Fuel Economy (CAFE) standards promulgated by the National Highway Traffic
Safety Administration (NHTSA) set fuel economy targets, in miles per gallon, for newly manufactured passenger cars
and light trucks sold in the United States. These standards have the co-benefit of reducing GHG emissions from these
vehicles.
14 For more information, see CRS Report R46719, Green Building Overview and Issues, by Corrie E. Clark.
15 The Energy Policy Act of 2005 (P.L. 109-58), amended by the Energy Independence and Security Act of 2007
(EISA; P.L. 110-140), established the Renewable Fuel Standard (RFS). The RFS includes scheduled volume mandates
that grow each year (starting with 9 billion gallons in 2008 and ascending to 36 billion gallons in 2022). EPA
administers the RFS. For more information, see CRS Report R44045, The Renewable Fuel Standard (RFS): Waiver
Authority and Modification of Volumes, by Kelsi Bracmort.
16 A comprehensive discussion of the history and factors that have played a role in the development of these rules is
beyond the scope of this report.
17 For example, EPA’s 2015 final rule establishing GHG emission standards for new fossil fuel-fired utility boilers and
natural gas-fired stationary combustion turbines remains in place. The New Source Performance Standard for new and
modified power plants relies in part on carbon capture and sequestration (CCS) technology to reduce emissions by
about 20% compared with the emissions of what was considered (at the time of the rule) a state-of-the-art coal-fired
plant without CCS. See EPA, “Standards of Performance for Greenhouse Gas Emissions from New, Modified, and
Reconstructed Stationary Sources: Electric Utility Generating Units,” 80 Federal Register 64509, October 23, 2015.
Congressional Research Service

5

U.S. Greenhouse Gas Emissions Trends and Projections from the Inflation Reduction Act

 In January 2021, EPA promulgated GHG emission standards for aircraft engines
equivalent to the standards adopted by the International Civil Aviation
Organization (ICAO).18
 In November 2021, EPA issued a proposed rule that would reduce methane and
other air pollution from new and existing sources in the oil and natural gas
industry.19 EPA issued a supplemental proposal in November 2022, which,
according to EPA, would “strengthen and expand” the 2021 proposal.20
 In December 2021, EPA finalized GHG emissions standards for passenger cars
and light trucks for Model Years (MY) 2023-MY2026.21
 In May 2022, EPA announced the initiation of a separate rulemaking to establish
multi-pollutant emission standards from light-duty and medium-duty vehicles for
MY2027 and later.22
 In September 2022, EPA solicited “pre-proposal” outreach with questions for
stakeholders regarding its strategy to address CO2 emissions from existing fossil-
fuel-fired power plants.23 (As mentioned above, EPA finalized regulations for
new fossil-fuel-fired power plants in 2015.) This potential rulemaking would
follow from the legal developments with the Obama Administration’s 2015 Clean
Power Plan (CPP) and the Trump Administration’s 2019 Affordable Clean
Energy (ACE) rule. Both the CPP and ACE rules were the subject of extensive
litigation, and neither was implemented.24
 In December 2022, EPA finalized regulations to address nitrogen oxide (NOx)
emissions from heavy-duty vehicles in MY2027 and beyond. The proposed rule
from March 2022 also included regulations addressing GHG emissions. EPA
stated that the agency would address these emissions in a separate rulemaking.25

18 EPA, “Control of Air Pollution From Airplanes and Airplane Engines: GHG Emission Standards and Test
Procedures,” 86 Federal Register 2136, January 11, 2021.
19 EPA, “Standards of Performance for New, Reconstructed, and Modified Sources and Emissions Guidelines for
Existing Sources: Oil and Natural Gas Sector,” 86 Federal Register 63110, November 15, 2021.
20 EPA, “Standards of Performance for New, Reconstructed, and Modified Sources and Emissions Guidelines for
Existing Sources: Oil and Natural Gas Sector Climate Review,” 87 Federal Register 74702, December 6, 2022.
21 EPA, “Revised 2023 and Later Model Year Light-Duty Vehicle Greenhouse Gas Emissions Standards,” 86 Federal
Register 74434, December 30, 2021.
22 For more information on this potential rulemaking, see EPA “Potential SBAR Panel: Multi-Pollutant Emissions
Standards for Model Years 2027 and Later Light-Duty and Medium-Duty Vehicles,” at https://www.epa.gov/reg-flex/
potential-sbar-panel-multi-pollutant-emissions-standards-model-years-2027-and-later-light.
23 See EPA, “Pre-Proposal Public Docket: Greenhouse Gas Regulations for Fossil Fuel-fired Power Plants,” at
https://www.epa.gov/stationary-sources-air-pollution/pre-proposal-public-docket-greenhouse-gas-regulations-fossil-
fuel; and EPA, “Questions for Consideration,” at https://downloads.regulations.gov/EPA-HQ-OAR-2022-0723-0002/
content.pdf.
24 For more background on these legal developments, see “West Virginia v. EPA: Greenhouse Gas Regulation and the
Major Questions Doctrine” in CRS Report R47276, Supreme Court Term October 2021: A Review of Selected Major
Rulings, coordinated by Valerie C. Brannon.
25 The final rule (signed December 20, 2022) is available at https://www.epa.gov/regulations-emissions-vehicles-and-
engines/final-rule-and-related-materials-control-air-pollution. EPA, “Control of Air Pollution from New Motor
Vehicles: Heavy-Duty Engine and Vehicle Standards,” 87 Federal Register 17414, March 28, 2022. According to EPA,
this regulation will be the first of three in a series of rulemakings that would set new standards for criteria pollutants,
such as fine particulate matter and nitrogen dioxide, and GHG emissions for heavy-duty vehicles. For more
information, see EPA, “Heavy-Duty 2027 and Beyond: Clean Trucks Proposed Rulemaking,” March 2022, at
https://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=P1014874.pdf.
Congressional Research Service

6

U.S. Greenhouse Gas Emissions Trends and Projections from the Inflation Reduction Act

State and Local Policies
In the absence of comprehensive federal controls on GHG emissions, some state and local
governments have taken a variety of actions—both legal mandates and voluntary efforts—for
approximately 20 years. Selected examples of currently implemented policies include the
following:
 California implements a GHG emissions cap-and-trade program that covers
electric power, selected industries, and fossil fuel distributors.26
 Eleven U.S. states participate in the Regional Greenhouse Gas Initiative
(RGGI),27 a cap-and-trade program that covers CO2 emissions from electric
power.
 Thirty states, three U.S. territories, and the District of Columbia require a
minimum amount of electricity generation by eligible sources such as
renewables.28
 Seventeen states have adopted California’s more stringent vehicle emissions
standards,29 and forty-five states and the District of Columbia provide incentives
for electric vehicles, hybrids, or both.
 The California Air Resources Board adopted regulations in August 2022 to phase
out the sale of conventional gas-powered vehicles by 2035.30 New York,
Washington, and Massachusetts have similar requirements in various stages of
development.
 Governors from 23 states and Puerto Rico announced a commitment to reduce
net GHG emissions from their states by at least 50%-52% below 2005 levels by
2030 and achieve net-zero GHG emissions no later than 2050.31

26 For more information, see the California Air Resources Board website at https://ww2.arb.ca.gov/our-work/programs/
cap-and-trade-program. Washington State established a comparable cap-and-trade program that is scheduled to start in
2023 (see State of Washington Department of Ecology, “Washington’s cap-and-invest program,” at
https://ecology.wa.gov/Air-Climate/Climate-Commitment-Act/Cap-and-invest).
27 The Regional Greenhouse Gas Initiative (RGGI) states are Connecticut, Delaware, Maine, Maryland, Massachusetts,
New Hampshire, New Jersey, New York, Rhode Island, Virginia, and Vermont. Through executive branch action,
Pennsylvania is seeking to join RGGI. Some policymakers in Pennsylvania’s legislative bodies have voiced strong
opposition to joining RGGI and the governor’s actions to join the program without enacting new legislation. In
addition, the governor of Virginia has proposed removing his state from RGGI.
28 Database of State Incentives for Renewables & Efficiency, “Renewable & Clean Energy Standards,” at
https://s3.amazonaws.com/ncsolarcen-prod/wp-content/uploads/2019/07/RPS-CES-June2019.pdf. See also CRS Report
R45913, Electricity Portfolio Standards: Background, Design Elements, and Policy Considerations, by Ashley J.
Lawson.
29 California Air Resources Board, “Low Emissions Vehicle Program,” at https://ww2.arb.ca.gov/our-work/programs/
low-emission-vehicle-program; and California Air Resources Board, “States that have Adopted California’s Vehicle
Standards under Section 177 of the Federal Clean Air Act,” at https://ww2.arb.ca.gov/sites/default/files/2022-05/
%C2%A7177_states_05132022_NADA_sales_r2_ac.pdf.
30 The regulations were sent to the state’s Office of Administrative Law, which will make a determination by
November 22, 2022 (see California Air Resources Board, “Advanced Clean Cars II,” at https://ww2.arb.ca.gov/
rulemaking/2022/advanced-clean-cars-ii).
31 The degree to which state and local governments can achieve these targets without federal action is uncertain, as the
legal authorities and jurisdictions over GHG emissions sources may be limited in some cases. U.S. Climate Alliance,
“U.S. Climate Alliance Commits to Achieve Net-Zero Emissions No Later than 2050,” press release, April 23, 2021, at
https://www.usclimatealliance.org/publications/newtargets.
Congressional Research Service

7

U.S. Greenhouse Gas Emissions Trends and Projections from the Inflation Reduction Act

Climate Change Legislation
Legislative Approaches Prior to the 117th Congress
Members of Congress have historically expressed a range of perspectives regarding climate
change issues. Members seeking to limit or remove GHG emissions from the atmosphere have
considered a range of policy options, including
 carbon pricing frameworks (e.g., carbon taxes or cap-and-trade programs);32
 sectoral approaches, such as a clean energy standard;
 research funding or tax policies that support low-emission technologies;
 creation of publicly funded entities to facilitate private investment into domestic
low-carbon, climate-resilient infrastructure (i.e., green banks);
 loan guarantees to support the development or deployment of low-emission
technologies; and
 support for adaptation and international cooperation.
Other legislative approaches have sought to prohibit certain approaches. For example, a number
of resolutions introduced in recent years have stated that multisector carbon pricing approaches
are not in the economic interests of the United States.33 In addition, some Members have
introduced bills that would limit the authority to regulate GHG emissions under the Clean Air
Act.
Votes on comprehensive climate change policy have been relatively rare in either chamber of
Congress.34 Prior to the 117th Congress, examples of enacted legislation involving climate change
issues included tax incentives to promote renewable energy sources and carbon capture and
sequestration efforts.35 The 116th Congress enacted the American Innovation and Manufacturing
(AIM) Act of 2020, which established a 15-year timeline to reduce domestic hydrofluorocarbons
(HFCs), a potent class of GHGs used in air conditioning and refrigeration equipment.36 The AIM
Act phasedown schedule aligns with international commitments to phase down HFCs under the

32 For more information, see CRS Report R45472, Market-Based Greenhouse Gas Emission Reduction Legislation:
108th Through 117th Congresses, by Jonathan L. Ramseur.
33 For example, between the 112th Congress and going through the 115th Congress, Members introduced resolutions in
both the House and Senate expressing the view that a carbon tax is not in the economic interests of the United States. In
2016 and 2018, the House passed resolutions “expressing the sense of Congress that a carbon tax would be detrimental
to the United States economy” (H.Con.Res. 89 and H.Con.Res. 119, respectively). In the 117th Congress, during debate
on S.Con.Res. 5, the Senate voted (50-50, not agreed to) on S.Amdt. 887, which would have established “a deficit-
neutral reserve fund relating to prohibiting a Federal carbon tax.”
34 One example is H.R. 2454, the American Clean Energy and Security Act of 2009 (“Waxman-Markey”), in the 111th
Congress, which would have established an economy-wide cap-and-trade system to reduce GHG emissions. The House
passed H.R. 2454 in 2009. Companion legislation in the Senate, S. 1733, was reported from the Committee on
Environment and Public Works; the bill was not brought up for consideration on the Senate floor.
35 For more information on the energy tax incentives available before the 117th Congress, see CRS Report R46865,
Energy Tax Provisions: Overview and Budgetary Cost, by Molly F. Sherlock.
36 The AIM Act was included in the Consolidated Appropriations Act, 2021 (P.L. 116-260, Division S, §103). The act
directed EPA to implement the requirements through regulations.
Congressional Research Service

8

U.S. Greenhouse Gas Emissions Trends and Projections from the Inflation Reduction Act

Kigali Amendment to the Montreal Protocol. The Senate advised and consented to the ratification
of the Kigali Amendment on September 21, 2022.37
Climate Change Legislation in the 117th Congress
During the 117th Congress, both President Biden and majority leadership in the House and the
Senate called for comprehensive approaches to address climate change. The following sections
focus on two enacted legislative measures in the 117th Congress: IIJA and the budget
reconciliation measure commonly referred to as the Inflation Reduction Act or IRA. These acts
include provisions that are likely to have direct or indirect effects on GHG emission levels,
particularly the provisions in IRA. In addition, both of these acts include provisions that address
other aspects of climate change policy, such as adaptation efforts. These acts and their potential
effects on GHG emissions are discussed below.
Beyond IIJA and IRA, some Members of the 117th Congress have introduced other proposals that
address climate change in some capacity. These proposals were referred to more than 35
committees,38 and some proposals were enacted. For example, P.L. 117-167 (often referred to as
the “CHIPS and Science Act”), enacted August 9, 2022, contains some provisions related to
climate change, including authorizations for appropriations for research on carbon removal and
alternative fuels, among other purposes.
Infrastructure Investment and Jobs Act
On November 15, 2021, President Biden signed the IIJA (P.L. 117-58). IIJA is a broad
infrastructure law that addresses a range of sectors, including transportation and energy, among
others. IIJA provisions include climate mitigation policies and programs in surface transportation
with increased funding for public transportation and intercity passenger rail.39 IIJA provisions
involve a number of energy issues that may have an effect on GHG emissions, including the
following:
 energy efficiency and renewable energy;
 electric grid reliability, resilience, and cybersecurity;
 carbon capture, utilization, and storage;
 hydrogen research and development;
 nuclear energy;
 battery manufacturing, recycling, and critical minerals; and
 fossil energy programs.40

37 U.S. Congress, Senate, Amendment to Montreal Protocol (“Kigali Amendment”), Senate Consideration of Treaty
Document 117-1, 117th Cong., 1st sess., November 2021. The vote was 69-27, with 4 not voting.
38 For more details, see CRS Report R46947, U.S. Climate Change Policy, coordinated by Richard K. Lattanzio; and
CRS Report R45472, Market-Based Greenhouse Gas Emission Reduction Legislation: 108th Through 117th
Congresses, by Jonathan L. Ramseur.
39 For more details, see CRS In Focus IF11921, Surface Transportation and Climate Change: Provisions in the
Infrastructure Investment and Jobs Act (P.L. 117-58), by William J. Mallett.
40 For more details on the energy provisions, see CRS Report R47034, Energy and Minerals Provisions in the
Infrastructure Investment and Jobs Act (P.L. 117-58), coordinated by Brent D. Yacobucci.
Congressional Research Service

9

U.S. Greenhouse Gas Emissions Trends and Projections from the Inflation Reduction Act

A number of studies have estimated the impact of IIJA on GHG emissions. For example, a 2022
study from Princeton University estimated that U.S. emissions would decrease to 26% below
2005 levels without IIJA and 27% below 2005 levels with IIJA.41 This analysis did not include
potential effects (e.g., changes in passenger and freight miles traveled) from IIJA funding for
transportation, rail, and public transit. However, a 2021 analysis from the Georgetown Climate
Center concluded that the emission effects from the IIJA transportation provisions are uncertain
and could result in an increase or decrease in emissions. This analysis concluded emission effects
would depend on implementation and funding decisions made by state, federal, and local
governments.42
Inflation Reduction Act
On August 16, 2022, President Biden signed H.R. 5376 (P.L. 117-169), the IRA. The eight titles
in IRA address a range of issues, including climate change matters, among other policy
objectives. Each of the titles contain some number of provisions that directly or indirectly address
issues related to climate change, including reduction of U.S. GHG emissions or promotion of
adaptation and resilience to climate change impacts.43 Many of these provisions involve funding
for new or existing programs, including provisions that
 modify, extend, or provide new tax credits for electricity from “clean” and
renewable resources, alternative fuels, energy efficiency, manufacturing, and
clean vehicles;44
 impose a charge on methane emissions from specific oil and gas facilities;45
 provide funding for carbon removal activities;
 provide funding for energy efficiency projects;
 provide funding for low-emission fuels and technologies;
 provide funding for energy rebates and efficiency, electricity transmission,
industrial and energy infrastructure, and advanced vehicle manufacturing;
 provide funding for offshore wind energy development and increase royalty rates
for federal land and offshore oil and gas leases;
 provide funding to support zero-emission technologies in low-income areas;
 provide funding for use of low-carbon construction materials in transportation
projects;
 provide funding to for low-carbon building materials and low- or no-emission
energy projects; and
 provide funding for a tribal electrification program.

41 Princeton REPEAT, Preliminary Report.
42 Georgetown Climate Center, “Issue Brief: Estimating the Greenhouse Gas Impact of Federal Infrastructure
Investments in the IIJA,” December 2021, at https://www.georgetownclimate.org/articles/federal-infrastructure-
investment-analysis.html.
43 For more details on the climate change-related provisions of the budget reconciliation measure commonly referred to
as the Inflation Reduction Act of 2022 (IRA), see CRS Report R47262, Inflation Reduction Act of 2022 (IRA):
Provisions Related to Climate Change, coordinated by Jane A. Leggett and Jonathan L. Ramseur.
44 For more information on these tax provisions, see CRS Report R47202, Tax Provisions in the Inflation Reduction Act
of 2022 (H.R. 5376), coordinated by Molly F. Sherlock.
45 The methane charge is the first federal price (i.e., carbon price) on GHG emissions.
Congressional Research Service

10

link to page 15 link to page 5 U.S. Greenhouse Gas Emissions Trends and Projections from the Inflation Reduction Act

U.S. GHG Emission Reduction Goals
The United Nations Framework Convention on Climate Change (UNFCCC) is the principal
international treaty to acknowledge and address human-driven climate change. The United States
ratified the treaty in 1992.46 Pursuant to the 2015 Paris Agreement (PA), the second major
subsidiary agreement under the UNFCCC,47 countries must submit GHG emission reduction
pledges referred to as a Nationally Determined Contribution (NDC). Targets and actions pledged
in NDCs are nonbinding. Participating countries must update their NDCs every five years. U.S.
NDCs include the following:
 2015 NDC: reduce net GHG emissions48 by 26%-28% below 2005 levels by
2025; and
 2021 NDC: reduce net GHG emissions by 50%-52% below 2005 levels by 2030.
According to the Biden Administration, the 2021 NDC “exceeds a straight-line path to achieve
net-zero emissions, economy-wide, by no later than 2050.”49
Figure 3 illustrates actual U.S. GHG emissions (including an estimate for 2021) and the
reduction targets for 2025 and 2030 and Biden’s goal to achieve net-zero emissions in 2050. As
the figure indicates, 2020 emissions were 21% below 2005 levels. Estimated emissions in 2021
were 16% below 2005 levels.

46 U.S. Treaty Number 102-38.
47 See CRS In Focus IF11746, United States Rejoins the Paris Agreement on Climate Change: Options for Congress,
by Jane A. Leggett.
48 Net emissions includes the sum of gross emissions estimates and removal estimates (see footnote 4).
49 The White House, “The United States of America Nationally Determined Contribution Reducing Greenhouse Gases
in the United States: A 2030 Emissions Target,” April 22, 2021, at https://www4.unfccc.int/sites/ndcstaging/
PublishedDocuments/United%20States%20of%20America%20First/
United%20States%20NDC%20April%2021%202021%20Final.pdf.
Congressional Research Service

11

U.S. Greenhouse Gas Emissions Trends and Projections from the Inflation Reduction Act

Figure 3. Historical U.S. GHG Net Emissions Compared with U.S. Emissions Targets

Source: Prepared by CRS; actual U.S. GHG emissions from EPA GHG Inventory.
Notes: NDC = Nationally Determined Contribution pursuant to the United Nations Framework Convention
on Climate Change (UNFCCC) Paris Agreement. MMTCO2e = mil ion metric tons of CO2 equivalent. This
measure is used because GHGs vary by global warming potential (GWP). GWP is an index that allows
comparisons of the heat-trapping ability of different gases over a period of time. The GHG emissions in the
figure are net GHG emissions. Net GHG emissions account for removals of CO2 emissions from the atmosphere
by emission sinks, such as forests, vegetation, and soils. The U.S. NDC is measured in terms of net emissions.
CRS calculated the 2021 U.S. GHG emission estimate based on CO2 data from EIA. EIA provides energy-related
CO2 emissions on a more up-to-date schedule than EPA’s inventory, which includes GHGs from all sources. The
CO2 emissions in EIA’s reports account for approximately 80% of total U.S. GHG emissions, and their
fluctuations generally track with the annual percentage changes in total GHG emissions from EPA’s inventories.
EIA data indicate that CO2 emissions from the energy sector increased by 7% between 2020 and 2021. CRS
applied this percentage increase to total net GHG emissions in 2020, resulting in an estimate of 5,588 MMTCO2e
in 2021 (see EIA, Monthly Energy Review, September 2022, at https://www.eia.gov/totalenergy/data/monthly/
#environment).
U.S. GHG Emission Estimates in 2030
Several recent analyses from groups in the private sector, academia, and the federal government
used computer simulation models to prepare estimates of U.S. net GHG emissions through
2030.50 These models compare baseline scenarios (without IRA) with emission scenarios that
include IRA. Based on the results from these models, IRA’s climate change provisions are likely
to result in net GHG emissions reductions as compared to emissions scenarios without IRA. Each
of the analyses included multiple IRA scenarios to account for uncertain factors, such as future oil

50 Rhodium Group, A Turning Point for US Climate Progress: Assessing the Climate and Clean Energy Provisions in
the Inflation Reduction Act, August 12, 2022, at https://rhg.com/research/climate-clean-energy-inflation-reduction-act/
(hereinafter Rhodium Group, A Turning Point for US Climate Progress); Princeton REPEAT, Electricity Transmission;
Energy Innovation, Modeling the Inflation Reduction Act Using the Energy Policy Simulator, August 23, 2022, at
https://energyinnovation.org/publication/modeling-the-inflation-reduction-act-using-the-energy-policy-simulator/
(hereinafter Energy Innovation, Modeling the Inflation Reduction Act); and Department of Energy, “The Inflation
Reduction Act Drives Significant Emissions Reductions and Positions America to Reach Our Climate Goals,” August
2022, at https://www.energy.gov/sites/default/files/2022-08/8.18%20InflationReductionAct_Factsheet_Final.pdf.
Congressional Research Service

12

link to page 16
U.S. Greenhouse Gas Emissions Trends and Projections from the Inflation Reduction Act

and natural gas prices, the rate of increase in electricity transmission, and implementation of IRA
provisions, among others.
Figure 4 illustrates the results of these analyses and indicates that under baseline conditions
(without IRA), U.S. net GHG emissions would decrease by 23% to 35% by 2030 compared with
2005 levels. The models estimated that with the addition of IRA, U.S. net GHG emissions would
decrease by 30% to 43% by 2030 compared with 2005 levels.
Figure 4. Net U.S. GHG Emissions, Selected Emission Estimates, and U.S. NDC

Source: Prepared by CRS; actual U.S. GHG emissions from EPA GHG Inventory; Rhodium Group emission
estimates from Rhodium Group, A Turning Point for US Climate Progress: Assessing the Climate and Clean Energy
Provisions in the Inflation Reduction Act, August 12, 2022, at https://rhg.com/research/climate-clean-energy-inflation-
reduction-act/ (hereinafter Rhodium Group, A Turning Point for US Climate Progress); and Princeton estimates from
Princeton University REPEAT, Electricity Transmission is Key to Unlock the Full Potential of the Inflation Reduction Act,
September 2022, at https://repeatproject.org/docs/REPEAT_IRA_Transmission_2022-09-22.pdf; Energy
Innovation estimates from Energy Innovation, Modeling the Inflation Reduction Act Using the Energy Policy Simulator,
August 23, 2022, at https://energyinnovation.org/publication/modeling-the-inflation-reduction-act-using-the-
energy-policy-simulator/; and Department of Energy estimates from Department of Energy, “The Inflation
Reduction Act Drives Significant Emissions Reductions and Positions America to Reach Our Climate Goals,”
August 2022, https://www.energy.gov/sites/default/files/2022-08/
8.18%20InflationReductionAct_Factsheet_Final.pdf.
Notes: NDC = National y Determined Contribution pursuant to the UNFCCC Paris Agreement. MMTCO2e =
mil ion metric tons of CO2 equivalent. This measure is used because GHGs vary by global warming potential
(GWP). GWP is an index that allows comparisons of the heat-trapping ability of different gases over a period of
time. The GHG emissions in the figure are net GHG emissions. Net GHG emissions account for removals of
CO2 emissions from the atmosphere by emission sinks, such as forests, vegetation, and soils. The U.S. NDC is
measured in terms of net emissions.
Congressional Research Service

13

link to page 17 link to page 17 link to page 16
U.S. Greenhouse Gas Emissions Trends and Projections from the Inflation Reduction Act

The 2021 U.S. GHG emission estimate is calculated by CRS based on CO2 data from EIA. EIA provides energy-
related CO2 emissions on a more up-to-date schedule than EPA’s inventory, which includes GHGs from all
sources. The CO2 emissions in EIA’s reports account for approximately 80% of total U.S. GHG emissions, and
their fluctuations generally track with the annual percentage changes in total GHG emissions from EPA’s
inventories. EIA data indicate that CO2 emissions from the energy sector increased by 7% between 2020 and
2021. CRS applied this percentage increase to total net GHG emissions in 2020, resulting in an estimate of 5,588
MMTCO2e in 2021 (see EIA, Monthly Energy Review, September 2022, at https://www.eia.gov/totalenergy/data/
monthly/#environment).
The modeling results all find that most of IRA’s projected emissions reductions come from the
electric power sector in the 2030 time frame. As an illustrative example, Figure 5 displays the
results from one of the studies,51 depicting the GHG emissions reductions estimated by sector:
electric power, industry, transportation, and carbon removal. Compared with a baseline scenario
(without IRA), electric power sector emissions decrease by 51%. In contrast, transportation sector
emissions are projected to remain roughly level (decrease by 1%).52 As discussed below, many of
the IRA provisions may take longer than 2030 to have full effect, such as tax incentives for
electric or zero-emission vehicles that would penetrate vehicle markets slowly and would have
more influence on GHG emissions after 2030. Therefore, these estimates do not represent a full
accounting of potential effects of the law.
Figure 5. Estimated GHG Emissions Reductions by Sector in 2030
Based on Rhodium Group Modeling

Source: Prepared by CRS; emissions estimates from Rhodium Group, A Turning Point for US Climate Progress.
Notes: MMTCO2e = mil ion metric tons of CO2 equivalent. This measure is used because GHGs vary by global
warming potential (GWP). GWP is an index that allows comparisons of the heat-trapping ability of different
gases over a period of time. Carbon removal includes “forest and soil practices, direct air capture and other
actions.”

51 Figure 5 depicts the results from the Rhodium Group’s “central case,” which is identified as “Case 2” in Figure 4.
52 The Energy Innovation model produced comparable results for the electric power and transportation sectors (Figure 2
in Energy Innovation estimates from Energy Innovation, Modeling the Inflation Reduction Act). The Princeton model
produced larger reductions in the transportation sector compared with the other models (Princeton REPEAT, Electricity
Transmission, p. 9).
Congressional Research Service

14

link to page 16 U.S. Greenhouse Gas Emissions Trends and Projections from the Inflation Reduction Act

Considerations for the 118th Congress
The GHG emissions modeling results presented in this report may be instructive for policymakers
as they consider climate change policies in the 118th Congress. As Figure 4 illustrates, none of the
modeled scenarios indicate that the United States would meet its GHG emissions target for 2030:
50%-52% below 2005 levels. The range of estimates for emissions levels in 2030 indicate the
amount of uncertainty in the modeling results.
In addition to the 2030 GHG emissions estimates, some of the models provide additional analysis,
examining the role of particular factors in the estimates. One of the factors generating the
uncertainty and the range of estimated emissions reductions in 2030 is the rate in which
electricity transmission is expected to expand over the next decade. The Princeton model
examined the specific role of this factor by isolating this variable in its modeling scenarios.53 The
Princeton model found that the annual rate of transmission expansion is likely to play a pivotal
role in the degree to which IRA provisions reduce U.S. GHG emissions. Historically, electricity
transmission has expanded by about 1% per year. One model indicates that less than 20% of the
potential emission reduction from IRA would be realized if transmission expansion remains at
this pace. To achieve the full potential of IRA’s emissions reductions, the same model indicates
that transmission would need to expand by 2.3% per year.54 The 117th Congress enacted
legislation aimed at accelerating transmission development (e.g., IIJA) and considered a range of
issues, such as permit reform, that could increase expansion.55 The IRA modeling results and the
role of transmission expansion may provide further context for the consideration of these issues in
the 118th Congress.
In addition, authors of some of the models note that, in some cases, IRA provisions could not be
included in their emissions analyses. The treatment of these and other provisions vary by
simulation model.56 Some of the provisions not modeled include those that promote the
development of technologies that could result in emissions reductions over a longer time horizon
(i.e., beyond 2030), but the estimated effects of these provisions is uncertain.
Some of the models examine the effects of IRA provisions beyond the 2030 time horizon. These
models indicate that the emission effects of the IRA climate provisions are expected to produce
results on different time horizons. In some cases, the results indicate greater emission reductions
are achieved after 2030, for example:
 The transportation-related provisions are likely to take longer to yield GHG
emissions reductions than the provisions affecting the electric power sector due
to the duration of vehicle stock turnover cycles.57 For instance, the Princeton

53 The other modeling groups did not specifically analyze the role of transmission. For example, the Energy Innovation
model assumed, among other things, that “necessary transmission will be built, interconnection delays are addressed”
(Energy Innovation, Modeling the Inflation Reduction Act).
54 Princeton REPEAT, Electricity Transmission.
55 For further information, see CRS In Focus IF12253, Introduction to Electricity Transmission, by Ashley J. Lawson.
56 For example, the Princeton study states that such provisions include the tax incentives for hydrogen production and
support advanced energy and manufacturing activities. See, for example, Princeton REPEAT, Preliminary Report, pp.
16-18; the Energy Innovation study states, “some provisions or funding mechanisms were excluded from the modeling
due to difficulty translating certain spending categories or incentives into emissions reductions. These programs could
likely yield small additional GHG reductions beyond what we have modeled.”
57 See, for example, David R. Keith et al., “Vehicle Fleet Turnover and the Future of Fuel Economy,” Environmental
Research Letters, 2019. This study found that “it takes 19.6 years for the new technology to account for 90% of the on-
road fleet.”
Congressional Research Service

15

U.S. Greenhouse Gas Emissions Trends and Projections from the Inflation Reduction Act

study indicates that the emissions reductions in 2035 in the transportation sector
are almost double the reductions in 2030.58 In addition, the Energy Innovation
study states that transportation emissions reductions in 2035 or 2040 will be
“significantly greater than in 2030 given the stock turnover dynamic.”59
 Carbon capture and storage activity is estimated by some of models to increase
substantially after 2030. For example, the Rhodium Group study estimated that
installed carbon capture would more than double between 2030 and 2035.60 The
Princeton study indicated similar results.61
If Members want to incentivize U.S. GHG emissions reduction beyond the projections from the
models discussed in this report, a range of policy options remain available. IRA contains a
number of climate-related provisions across multiple economic sectors. The general approach of
IRA’s climate provisions is to promote GHG reduction through tax incentives and direct funding.
Policymakers could increase the funding amounts or tax incentives in these provisions.
Alternatively, policymakers could employ different approaches in subsequent legislation. Options
include market-based approaches, such as carbon pricing mechanisms (e.g., fee on emissions or a
cap-and-trade program) or regulatory standards for particular facilities or sectors.62 As discussed
above, to some degree, such efforts are underway at the state level. The authors of the studies
discussed in this report point out that the IRA climate provisions may support the development of
additional requirements from the federal government or state and local governments by reducing
the costs of lower-carbon energy sources and technologies. If these additional policies are
implemented, some argue, they may help achieve the 2030 target.63
In addition, a range of regulatory actions from the Biden Administration (discussed above) may
contribute to further emissions reductions over the next decade and beyond. The role of these
regulations is uncertain, as their implementation is likely to face opposition from policymakers
and stakeholders.

Author Information

Jonathan L. Ramseur

Specialist in Environmental Policy

58 Princeton REPEAT, Electricity Transmission, p. 5. In addition, the Energy Innovation study states “transportation
emissions reductions in 2035 or 2040 will be significantly greater than in 2030 given the stock turnover dynamic.”
Energy Innovation, Modeling the Inflation Reduction Act.
59 Energy Innovation, Modeling the Inflation Reduction Act.
60 Rhodium Group, A Turning Point for US Climate Progress, p. 6. For further information on carbon capture and
sequestration, see CRS Report R44902, Carbon Capture and Sequestration (CCS) in the United States, by Angela C.
Jones and Ashley J. Lawson.
61 Princeton REPEAT, Preliminary Report, figure on p. 13.
62 For more discussion of general approaches to GHG emissions mitigation, see CRS In Focus IF11791, Mitigating
Greenhouse Gas Emissions: Selected Policy Options, by Jonathan L. Ramseur et al.
63 See, for example, Rhodium Group, A Turning Point for US Climate Progress.
Congressional Research Service

16

U.S. Greenhouse Gas Emissions Trends and Projections from the Inflation Reduction Act

Acknowledgments
Amber Wilhelm, CRS Visual Information Specialist, helped create many of the figures in this
report.
The brief discussion of the history of U.S. climate change policies in this report is based on a
more comprehensive discussion from CRS Report R46947, U.S. Climate Change Policy,
coordinated by Richard K. Lattanzio.

Disclaimer
This document was prepared by the Congressional Research Service (CRS). CRS serves as nonpartisan
shared staff to congressional committees and Members of Congress. It operates solely at the behest of and
under the direction of Congress. Information in a CRS Report should not be relied upon for purposes other
than public understanding of information that has been provided by CRS to Members of Congress in
connection with CRS’s institutional role. CRS Reports, as a work of the United States Government, are not
subject to copyright protection in the United States. Any CRS Report may be reproduced and distributed in
its entirety without permission from CRS. However, as a CRS Report may include copyrighted images or
material from a third party, you may need to obtain the permission of the copyright holder if you wish to
copy or otherwise use copyrighted material.

Congressional Research Service
R47385 · VERSION 1 · NEW
17