REGULATORY 

IMPACT ANALYSIS

Development of 

Social Cost of Carbon 

Estimates

Report to Congressional Requesters

July 2014

GAO-14-663

United States Government Accountability Office
United States Government Accountability Office

Highlights of GAO-14-663, a report to 

congressional requesters

July 2014

REGULATORY IMPACT ANALYSIS

Development of Social Cost of Carbon Estimates

Why GAO Did This Study

Executive Order 12866 directs federal 

agencies to assess the economic 

effects of their proposed significant 

regulatory actions, including a 

determination that a regulation’s 

benefits justify the costs. In 2008, a 

federal appeals court directed DOT to 

update a regulatory impact analysis 

with an estimate of the social cost of 

carbon—the dollar value of the net 

effects (damages and benefits) of an 

increase in emissions of carbon 

dioxide, a greenhouse gas. 

In 2009, the Interagency Working 

Group on Social Cost of Carbon was 

convened to develop estimates for use 

governmentwide, and it issued final 

estimates in its 2010 Technical 

Support Document. In 2013, the group

issued revised estimates that were 

about 50 percent higher than the 2010 

estimates, which raised public interest.

GAO was asked to review the working 

group’s development of social cost of 

carbon estimates. This report 

describes the participating entities and 

processes and methods they used to 

develop the 2010 and 2013 estimates. 

GAO reviewed executive orders, OMB 

guidance, the Technical Support 

Document, its 2013 update, and other 

key documents. GAO interviewed 

officials who participated in the working 

group on behalf of the EOP offices and 

agencies involved. GAO did not 

evaluate the quality of the working 

group’s approach. 

GAO is making no recommendations in 

this report. Of seven agencies, OMB 

and Treasury provided written or oral 

comments and generally agreed with 

the findings in this report. Other 

agencies provided technical comments 

only or had no comments. 

What GAO Found

To develop the 2010 and 2013 social cost of carbon estimates, the Office of 

Management and Budget (OMB) and Council of Economic Advisers convened

and led an informal interagency working group in which four other offices from 

the Executive Office of the President (EOP) and six federal agencies

participated. Participating agencies were the Environmental Protection Agency 

(EPA) and the Departments of Agriculture, Commerce, Energy, Transportation 

(DOT), and the Treasury. According to several working group participants, the 

working group included relevant subject-matter experts and the agencies likely to 

use the estimates in future rulemakings. According to OMB staff, there is no 

single approach for convening informal interagency working groups and no 

requirement that this type of working group should document its activities or 

proceedings. However, OMB and EPA participants stated that the working group 

documented all major issues discussed in the Technical Support Document, 

which is consistent with federal standards for internal control. According to the 

Technical Support Document and participants GAO interviewed, the working 

group’s processes and methods reflected the following three principles: 

• Used consensus-based decision making. The working group used a 

consensus-based approach for making key decisions in developing the 2010 

and 2013 estimates. Participants generally stated that they were satisfied 

that the Technical Support Document addressed individual comments on 

draft versions and reflected the overall consensus of the working group. 

• Relied on existing academic literature and models. The working group 

relied largely on existing academic literature and models to develop its 

estimates. Specifically, the working group used three prevalent academic 

models that integrate climate and economic data to estimate future economic 

effects from climate change. The group agreed on three modeling inputs

reflecting the wide uncertainty in the academic literature, including discount 

rates. Once the group reached agreement, EPA officials—sometimes with 

the assistance of the model developers—calculated the estimates. All other 

model assumptions and features were unchanged by the working group, 

which weighted each model equally to calculate estimates. After the 

academic models were updated to reflect new scientific information, such as 

in sea level rise and associated damages, the working group used the 

updated models to revise its estimates in 2013, resulting in higher estimates. 

• Took steps to disclose limitations and incorporate new information. The 

Technical Support Document discloses several limitations of the estimates 

and areas that the working group identified as being in need of additional 

research. It also sets a goal of revisiting the estimates when substantially 

updated models become available. Since 2008, agencies have published 

dozens of regulatory actions for public comment that use various social cost 

of carbon estimates in regulatory analyses and, according to working group 

participants, agencies received many comments on the estimates throughout

this process. Several participants told GAO that the working group decided to 

revise the estimates in 2013 after a number of public comments encouraged 

revisions because the models used to develop the 2010 estimates had been 

updated and used in peer-reviewed academic literature. 

View GAO-14-663. For more information, 

contact J. Alfredo Gómez at (202) 512-3841 or 

gomezj@gao.gov.
Page i GAO-14-663 Social Cost of Carbon

Letter 1

Background 3

Approach Used to Develop Estimates of the Social Cost of Carbon 8

Agency Comments 20

Appendix I Regulatory Actions, by Agency and Type of Social Cost of Carbon 

Estimates Used, 2008-2014 22

Appendix II Comments from the Department of the Treasury 30

Appendix III GAO Contact and Staff Acknowledgments 31

Tables

Table 1: Central Values for the Social Cost of Carbon Estimates 

Issued by the Interagency Working Group on Social Cost 

of Carbon in 2010 and 2013 7

Table 2: Offices and Agencies Participating in the Interagency 

Working Group on Social Cost of Carbon to Develop the 

2010 and 2013 Social Cost of Carbon Estimates 9

Table 3: Regulatory Actions, by Agency and Type of Social Cost 

of Carbon Estimates Used in the Regulatory Impact 

Analysis, 2008-2014 22

Contents
Page ii GAO-14-663 Social Cost of Carbon

Abbreviations

ADS-B Automatic Dependent Surveillance-Broadcast

ATC Air Traffic Control

DICE Dynamic Integrated Climate and Economy

DOT Department of Transportation

EOP Executive Office of the President

EPA Environmental Protection Agency

FUND Climate Framework for Uncertainty, Negotiation, 

and Distribution

NHTSA National Highway Traffic Safety Administration

OMB Office of Management and Budget

PAGE Policy Analysis of the Greenhouse Effect

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Page 1 GAO-14-663 Social Cost of Carbon

441 G St. N.W.

Washington, DC 20548

July 24, 2014

The Honorable David Vitter

Ranking Member

Committee on Environment and Public Works

United States Senate

The Honorable Tim Murphy

Chairman

Subcommittee on Oversight and Investigations

Committee on Energy and Commerce

House of Representatives

The Honorable John Culberson

House of Representatives

The Honorable Duncan Hunter

House of Representatives

To encourage a regulatory system that protects and improves health, 

safety, the environment, and the economy, without imposing 

unreasonable costs on society, federal agencies are required to assess 

the economic effects of proposed significant regulatory actions. Agencies 

can use regulatory impact analysis to assess whether a proposed 

regulation’s benefits justify the costs. For example, regulations aimed at 

benefiting society by decreasing health risks associated with air pollution 

may require regulated entities, such as power plants, to incur costs for 

installing pollution control technologies. According to Environmental 

Protection Agency (EPA) officials, beginning in 2008, some agencies’

regulatory impact analyses incorporated estimates of the social cost of 

carbon,1 which agencies use to value the net effects of reducing or 

 1

The social cost of carbon (measured in dollars per metric ton of carbon dioxide) is the 

monetized net effects (damages and benefits) associated with an incremental increase in 

carbon emissions in a given year. Estimates of the social cost of carbon depend on the 

data and the models used to calculate them and can include a wide range of damage 

categories, such as projected changes in net agricultural productivity, human health, and 

property damages from increased flood risk due to increased carbon emissions.

Monetization is the process of estimating the dollar value of benefits and costs. 
Page 2 GAO-14-663 Social Cost of Carbon

increasing carbon dioxide emissions.2 In 2009, in part because agencies 

used varying estimates of the social cost of carbon, the Executive Office 

of the President’s (EOP) Office of Management and Budget (OMB) and 

Council of Economic Advisers convened an interagency working group to 

develop social cost of carbon estimates for federal agencies to use in 

their regulatory impact analyses. The working group finalized its 

estimates in 2010 and included them in a document—called the Technical 

Support Document—that also provides guidance for agencies on using 

the estimates.3 In May 2013, the working group issued an update to the 

Technical Support Document that included revised estimates of the social 

cost of carbon.4 These 2013 estimates of the social cost of carbon were 

approximately 50 percent higher than the 2010 estimates, which raised 

public interest.

You asked us to review the interagency working group’s development of 

social cost of carbon estimates. This report describes the approach used, 

including participating entities and processes and methods, to develop 

the 2010 and 2013 social cost of carbon estimates for regulatory impact 

analysis.

To address this objective, we reviewed pertinent requirements and 

guidance, including executive orders and OMB guidance; the Technical 

Support Document and its 2013 update; published materials and 

presentations by working group participants on the development of the 

social cost of carbon estimates; and related GAO reports. We interviewed 

current and former federal officials or staff who participated in the working 

group on behalf of the EOP offices and agencies named in the Technical 

 2

Carbon dioxide is a greenhouse gas recognized as a major contributor to climate change. 

Concentrations of greenhouse gases—including carbon dioxide, methane, nitrous oxide, 

and synthetic chemicals such as fluorinated gases—trap heat in the atmosphere and 

prevent it from returning to space. 

3

Interagency Working Group on Social Cost of Carbon, United States Government, 

Technical Support Document: Social Cost of Carbon for Regulatory Impact Analysis under 

Executive Order 12866 (Washington, D.C.: February 2010). 

4

Interagency Working Group on Social Cost of Carbon, United States Government, 

Technical Support Document: Technical Update of the Social Cost of Carbon for 

Regulatory Impact Analysis under Executive Order 12866 (Washington, D.C.: May 2013). 

This document was reissued with minor technical corrections in November 2013. 
Page 3 GAO-14-663 Social Cost of Carbon

Support Document.5 We identified these participants by contacting all of 

the agencies and OMB and then following up with additional individuals 

identified during our discussions with them. Through this process, we 

interviewed over 20 individuals who participated in the working group to 

develop the estimates in the Technical Support Document or its 2013 

update, or both. We also corresponded with researchers who developed 

key academic materials the working group used. Our review describes 

the approach the working group used to develop estimates of the social 

cost of carbon; evaluating the quality of the approach is outside the scope 

of this review.

We conducted this performance audit from November 2013 to July 2014 

in accordance with generally accepted government auditing standards. 

Those standards require that we plan and perform the audit to obtain 

sufficient, appropriate evidence to provide a reasonable basis for our 

findings and conclusions based on our audit objectives. We believe that 

the evidence obtained provides a reasonable basis for our findings and 

conclusions based on our audit objectives.

Executive Order 12866 directs federal agencies to assess the potential 

costs and benefits of their significant regulatory actions, consisting of 

several categories of regulatory actions, including those likely to result in 

a rule that may have an annual effect on the economy of $100 million or 

more or that have a material adverse effect on the economy; a sector of 

the economy; productivity; competition; jobs; the environment; public 

health or safety; or state, local, or tribal governments or communities.6

Under the executive order, for regulatory actions expected to meet this 

 5

According to the Technical Support Document, the working group consisted of 

participants from the Council of Economic Advisers, Council on Environmental Quality, 

EPA, National Economic Council, Office of Energy and Climate Change, OMB, Office of 

Science and Technology Policy, and the Departments of Agriculture, Commerce, Energy, 

Transportation, and the Treasury. In March 2011, the Office of Energy and Climate 

Change joined the Domestic Policy Council. 

6

Exec. Order No. 12866, 58 Fed. Reg. 51,735 (Sept. 30, 1993). Other significant 

regulatory actions include those that are likely to result in a rule that may create a serious 

inconsistency or otherwise interfere with an action taken or planned by another agency; 

materially alter the budgetary impact of entitlements, grants, user fees, or loan programs 

or the rights and obligations of recipients thereof; or raise novel legal or policy issues 

arising out of legal mandates, the President’s priorities, or the principles set forth in 

Executive Order 12866. 

Background
Page 4 GAO-14-663 Social Cost of Carbon

threshold, or economically significant regulatory actions, agencies must 

also assess costs and benefits of reasonably feasible alternatives and

explain why the planned regulatory action is preferable to the identified 

alternatives. For each significant regulatory action, the agency is to 

develop the proposed regulation and associated regulatory impact 

analysis and submit them to OMB for formal review. After OMB concludes 

its review, the agency is to publish the proposed rule in the Federal 

Register for public comment. The agency is to issue a document 

summarizing its consideration of the public comments and, if appropriate, 

modify the proposed rule in response to the comments. This phase of 

regulatory development may also include further internal and external 

review. For significant regulatory actions, the agency is to submit the final 

regulatory impact analysis and regulation to OMB for review before it 

publishes the final rule.

In 2003, OMB issued Circular A-4 to provide guidance to federal agencies 

on the development of regulatory analysis as directed by Executive Order 

12866.7 Circular A-4 states that it is designed to assist agencies by 

defining good regulatory analysis and standardizing the way benefits and 

costs of federal regulatory actions are measured and reported. In 

particular, the guidance provides for systematic evaluation of qualitative 

and quantitative benefits and costs, including their monetization. Circular 

A-4 also provides guidance on the selection of discount rates to adjust the 

estimated benefits and costs for differences in timing.8 According to 

Circular A-4, a regulatory impact analysis should include an evaluation of 

the benefits and costs of the proposed action and any reasonable 

alternatives, as well as a description of assumptions and uncertainty.9 It 

acknowledges that agencies cannot analyze all regulations according to a 

 7

OMB, Circular A-4: Regulatory Analysis (Sept. 17, 2003). 

8

When the benefits and costs of a regulatory action will occur in the future, agencies must 

determine the present value of future benefits and costs by applying an appropriate 

discount rate—the interest rate used to convert benefits and costs occurring in different 

time periods to a common present value.

9

Circular A-4 states that agencies should discount future benefits and costs using rates of 

3 and 7 percent but notes that agencies may, in addition, consider a lower discount rate if 

a rule will have important intergenerational benefits or costs. In July 2014, we reported on 

the application of the guidance in Circular A-4 and the Technical Support Document and 

made recommendations to OMB to help clarify the relationship between those two 

documents. See GAO, Environmental Regulation: EPA Should Improve Adherence to 

Guidance for Selected Elements of Regulatory Impact Analyses, GAO-14-519

(Washington, D.C.: July 18, 2014).
Page 5 GAO-14-663 Social Cost of Carbon

formula, and that different regulations may call for different emphases in 

the analysis. Executive Order 13563, which reaffirmed and supplemented 

Executive Order 12866 in 2011, generally directs federal agencies to 

conduct regulatory actions based on the best available science.10 It also 

directs agencies to use the best available techniques to quantify benefits 

and costs accurately.

Federal agencies began including estimates of the social cost of carbon 

in regulatory impact analyses following a decision by the U.S. Court of 

Appeals for the Ninth Circuit. Specifically, in 2006, the Department of 

Transportation’s National Highway Traffic Safety Administration (NHTSA) 

issued a final rule on fuel economy standards for certain vehicles which, 

like other regulations at the time, did not include estimates of the social 

cost of carbon.11 The final rule stated that the agency had identified a 

benefit from a significant reduction in carbon dioxide emissions but stated 

that the dollar value of the benefit could not be determined because of the 

wide variation in published estimates of the social cost of carbon. In 2008, 

in response to a challenge from 11 states and several other 

organizations, the Ninth Circuit held that NHTSA had acted arbitrarily and 

capriciously by failing to monetize the value of carbon emissions 

reduction and directed NHTSA to include such a monetized value in an 

updated regulatory impact analysis for the regulation.12 The court stated 

that, “[w]hile the record shows that there is a range of values, the value of 

carbon emissions reduction is certainly not zero.”

13 Following the court’s 

decision, the Department of Energy, the Department of Transportation, 

and EPA incorporated a variety of individually developed estimates of the 

social cost of carbon into their regulatory analyses. These estimates were 

derived from academic literature and ranged, in general, from $0 to $159 

(in 2006, 2007, or 2008 dollars) per metric ton of carbon dioxide emitted 

 10Exec. Order No. 13563, 76 Fed. Reg. 3821 (Jan. 18, 2011). 

11Average Fuel Economy Standards for Light Trucks Model Years 2008-2011, 71 Fed. 

Reg. 17,566 (Apr. 6, 2006). According to EPA officials, other regulations at the time did 

not typically quantify changes in carbon emissions. 

12Ctr. For Biological Diversity v. Nat’l Highway Traffic Safety Admin., 538 F.3d 1172, 1203 

(9th Cir. 2008). The Ninth Circuit issued the 2008 opinion after vacating and withdrawing 

its prior opinion, 508 F.3d 508, issued on Nov. 15, 2007. 

13Id. at 1200. 
Page 6 GAO-14-663 Social Cost of Carbon

in 2007. They also varied in whether they reflected domestic or global 

measures of the social cost of carbon.14

In early 2009, in part to improve consistency in agencies’ use of social 

cost of carbon estimates for regulatory impact analysis, OMB’s Office of 

Information and Regulatory Affairs and the Council of Economic Advisers 

convened the Interagency Working Group on Social Cost of Carbon. The 

working group developed interim governmentwide social cost of carbon 

estimates based on an average of selected estimates published in 

academic literature. The interim estimates first appeared—and, thus, 

were first available for public review—in August 2009 in the Department 

of Energy’s final rule on energy standards for vending machines.15

Agencies subsequently incorporated the interim estimates into several 

published regulatory actions that sought public comments to inform the 

development of final estimates for future use. The middle or “central”

value for the range of interim estimates was $19 (in 2006 dollars) per 

metric ton of carbon dioxide emitted in 2007.16

In October 2009, after developing the interim estimates, the working 

group reassembled to begin developing the final social cost of carbon 

estimates issued in the Technical Support Document. While the Technical 

Support Document is dated February 2010, it was first released publicly in 

March 2010 as an appendix to the Department of Energy’s final rule on 

energy standards for small electric motors.17 Subsequently, dozens of 

published regulatory actions incorporated the estimates. The Technical 

 14The benefits and costs of reducing most greenhouse gas emissions, including carbon 

dioxide, differ from most other benefits and costs in at least two respects: (1) greenhouse 

gas emissions can contribute to global damages even when emitted in the United States 

because these emissions can disperse widely throughout the atmosphere, and (2) these 

emissions generally remain in the atmosphere for years, causing subsequent long-term 

damages. While Circular A-4 states that agencies should generally estimate domestic 

benefits and costs of regulations, it also provides latitude to include global economic 

effects resulting from regulations when relevant and states that such effects should be 

reported separately and in addition to domestic effects. 

15Energy Conservation Program: Energy Conservation Standards for Refrigerated Bottled 

or Canned Beverage Vending Machines, 74 Fed. Reg. 44,914 (Aug. 31, 2009). 

16The working group calculated five interim estimates of the social cost of carbon using 

different discount rate scenarios and referred to $19—the middle of the five estimates—as 

the “central value.”

17Energy Conservation Program: Energy Conservation Standards for Small Electric 

Motors, 75 Fed. Reg. 10,874 (Mar. 9, 2010). 
Page 7 GAO-14-663 Social Cost of Carbon

Support Document states that the working group agreed to regularly 

update the social cost of carbon estimates as the research underlying the 

estimates evolves. In June 2013, after using the 2010 estimates in an 

earlier proposal of the rule, the Department of Energy’s final rule on 

energy standards for microwaves was the first regulatory action to 

incorporate the revised estimates developed by the working group in the 

2013 update to the Technical Support Document.18 Table 1 shows the 

central values for the range of 2010 and 2013 social cost of carbon 

estimates for carbon emissions occurring in selected years.

Table 1: Central Values for the Social Cost of Carbon Estimates Issued by the 

Interagency Working Group on Social Cost of Carbon in 2010 and 2013

Dollars are 2007 dollars per metric ton of carbon dioxide

Year 2010 central values 2013 central values

2010 $21 $32

2020 26 43

2030 33 52

2040 39 61

2050 $45 $71

Source: Interagency Working Group on Social Cost of Carbon’s Technical Support Document and 2013 update. | GAO-14-663

Note: The Technical Support Document states that the working group calculated the social cost of 

carbon for emissions occurring in multiple future years to cover the time horizons anticipated for 

upcoming regulatory analysis. When the benefits and costs of a regulatory action will occur in the 

future, agencies must determine the present value of future benefits and costs by applying an 

appropriate discount rate—the interest rate used to convert benefits and costs occurring in different 

periods to a common present value. According to the Technical Support Document, the social cost of 

carbon estimates increase over time because future emissions are expected to produce larger 

incremental damages as the environment and the economy become more stressed in response to 

greater climate change. The working group selected four values of the social cost of carbon for 

regulatory analysis. The first three values are based on the average of estimates calculated at 

discount rates of 2.5 percent, 3 percent, and 5 percent, and the fourth value was included to 

represent higher-than-expected economic impacts at the 3 percent discount rate. The Technical 

Support Document refers to the average of estimates calculated at the 3 percent discount rate as the 

“central value” of the social cost of carbon and states that agencies should consider all four values 

when conducting regulatory analyses.

Appendix I lists regulatory actions from 2008 to 2014 and the type of 

social cost of carbon estimates (i.e., individually developed, interim, 2010, 

or 2013) incorporated in the actions’ regulatory analyses.

 18Energy Conservation Program: Energy Conservation Standards for Standby Mode and 

Off Mode for Microwave Ovens, 78 Fed. Reg. 36,316 (June 17, 2013). 
Page 8 GAO-14-663 Social Cost of Carbon

According to the Technical Support Document and participants we 

interviewed, the working group consisted of participants representing six 

EOP offices and six federal agencies and was convened under Executive 

Order 12866. The working group’s processes and methods for developing 

the estimates reflected three key principles. Specifically, according to 

participants, the working group (1) used consensus-based decision 

making; (2) relied largely on existing academic literature and models, 

including technical assistance from outside resources; and (3) took steps 

to disclose limitations and incorporate new information by considering 

public comments and revising the estimates as updated research became 

available.

According to the Technical Support Document and participants we spoke 

with, OMB and the Council of Economic Advisers convened and led the 

working group, and four other EOP offices and six federal agencies 

actively participated in the group. According to several participants, the 

participating EOP offices included the relevant subject-matter experts to 

best contribute on behalf of the EOP,19 and the other participating 

agencies were those likely to conduct rulemakings affecting carbon 

emissions and, therefore, use the social cost of carbon estimates in the 

future. For example, EPA and the Department of Energy have issued 

numerous rules using the social cost of carbon estimates (see app. I).

OMB staff and EPA officials told us that OMB and the Council of 

Economic Advisers decided which EOP offices and federal agencies to 

invite to participate in the working group and, according to participants we 

interviewed from several agencies, each agency that chose to participate 

decided which of its internal offices would send representatives. OMB 

staff stated that any federal agency was welcome to participate in the 

working group, and EPA officials told us that at least two invited agencies 

declined to participate. OMB staff recalled that the working group 

generally included up to several participants from each participating office 

and agency and numbered approximately two dozen participants in total. 

 19We previously reported that four of these EOP offices—the Council on Environmental 

Quality, Office of Energy and Climate Change, OMB, and Office of Science and 

Technology Policy—provide high-level policy direction for federal climate change 

programs and activities and commonly lead formal and informal interagency initiatives on 

related issues. See GAO, Climate Change: Improvements Needed to Clarify National 

Priorities and Better Align Them with Federal Funding Decisions, GAO-11-317

(Washington, D.C.: May 20, 2011). 

Approach Used to 

Develop Estimates of 

the Social Cost of 

Carbon

Participating Entities
Page 9 GAO-14-663 Social Cost of Carbon

Table 2 lists the 12 participating offices and agencies, along with the 

internal offices they sent to represent them on the working group.

Table 2: Offices and Agencies Participating in the Interagency Working Group on Social Cost of Carbon to Develop the 2010 

and 2013 Social Cost of Carbon Estimates

Participating office or agency 2010 estimates 2013 estimates

Executive Office of the President

Council of Economic Advisers X a X

Council on Environmental Quality X X

National Economic Council X X

Office of Energy and Climate Change X b X

Office of Management and Budgeta X

Office of Information and Regulatory Affairs

X

Office of Science and Technology Policy X X

Federal agencies

Department of Agriculture

• Office of the Chief Economist X X

Department of Commercec

• International Trade Administration, Office of 

Competition and Economic Analysis

X d

• National Oceanic and Atmospheric Administration, 

National Marine Fisheries Servicee X

Department of Energyf

• Office of Climate Change Policy and Technology X g X

Department of Transportation

• Office of the Secretary X X

• Volpe, The National Transportation Systems Center X

Department of the Treasury

• Office of Economic Policy X

• Office of International Affairs, Office of Environment 

and Energy 

X X

Environmental Protection Agency

• Office of Air and Radiation, Office of Atmospheric 

Programs

X X

• Office of Policy, National Center for Environmental 

Economics

X X

Source: GAO analysis of information provided by the Office of Management and Budget, Environmental Protection Agency, and Departments of Agriculture, Commerce, Energy, Transportation, and the 

Treasury. | GAO-14-663

a

The Council of Economic Advisers and the Office of Management and Budget convened and led the 

working group to develop the 2010 and 2013 estimates.

b

In March 2011, the Office of Energy and Climate Change joined the Domestic Policy Council.
Page 10 GAO-14-663 Social Cost of Carbon

c

An official from the Department of Commerce’s Economics and Statistics Administration told us that 

he attended two working group meetings as an observer during the development of the 2013 

estimates, but that he did not review any materials produced by the group or otherwise contribute to 

the development of the estimates.

d

The International Trade Administration’s Office of Competition and Economic Analysis is now known 

as the Office of Trade and Economic Analysis.

e

An official from the Department of Commerce’s National Oceanic and Atmospheric Administration 

told us that she participated in the working group to develop the 2010 estimates while serving on 

detail to the Office of Science and Technology Policy.

f

A former Administrator of the Energy Information Administration told us that he participated as a 

technical advisor to the working group to develop the 2010 estimates and not as a representative of 

the Department of Energy. Participants told us that the Energy Information Administration also sent a 

representative to some working group meetings as an observer during the development of the 2013 

estimates.

g

The Office of Climate Change Policy and Technology is now known as the Office of Climate, 

Environment, and Efficiency.

In establishing the working group, several participants told us that OMB 

and the Council of Economic Advisers made efforts to ensure that the 

group’s members, collectively, brought the necessary technical expertise 

for developing social cost of carbon estimates. For example, according to 

these participants and EPA documentation, participants from the EOP 

offices included individuals with expertise in pertinent topics, such as 

economics and climate science. The former Deputy Assistant Secretary 

for Environment and Energy at the Department of the Treasury stated that 

he was invited to participate in the working group because of his prior 

experience researching ways to discount costs and benefits across 

generations. In addition, the former Administrator of the Energy 

Information Administration told us that he was asked to participate, in 

part, based on his previous experience evaluating climate models while 

conducting research with the National Academy of Sciences. According to 

an OMB staff member, the six participating federal agencies were also 

responsible for ensuring that they provided adequate technical expertise 

to the working group. Agency representatives included environmental 

economists and climate scientists, among other key professionals. 

According to EPA documentation, participants from EPA also provided 

technical expertise in climate science, economics, and academic 

modeling to the broader group, as needed.

When the working group reconvened in 2013 to update the estimates, the 

same EOP offices and agencies generally participated, although some of 

the individuals participating on behalf of offices or agencies changed, in 

part due to individuals changing positions or leaving the government 

altogether. Also, some participants who previously had been serving 

details at other participating agencies had returned to their home 

agencies. For example, certain participants who were on detail to the 
Page 11 GAO-14-663 Social Cost of Carbon

Council of Economic Advisers during the development of the 2010 

Technical Support Document instead represented EPA on the working 

group during the development of the 2013 update.

According to the Technical Support Document, the working group was 

convened under the broad direction of Executive Order 12866 for 

agencies to assess the costs and benefits of intended regulations.20 In 

addition, participants from several agencies told us that the executive 

order was the key requirement driving the working group’s effort to 

develop social cost of carbon estimates. OMB staff stated that, while 

there is no single requirement or other approach for convening 

interagency working groups, it is appropriate for OMB to form interagency 

working groups to collaborate on policy or analytic needs identified under 

Executive Order 12866. These OMB staff members said that, instead of 

being organized under a written agreement or other requirements, the 

working group was an informal interagency working group with no charter 

or other convening document. According to OMB staff, there was no 

requirement that the informal working group should document its activities 

or proceedings, including the meetings held or specific discussions that 

occurred at each. However, OMB staff and EPA officials stated that all 

major issues discussed during working group meetings are documented 

in the Technical Support Document and its 2013 update, which is 

consistent with the control activities standard in the federal standards for 

internal control.21 We have also reported that interagency working groups 

use a variety of mechanisms to implement interagency collaborative 

efforts, including temporary working groups,22 and that not all 

collaborative arrangements, particularly those that are informal, need to 

be documented through written guidance and agreements.23

 20The 2013 update to the Technical Support Document adds that Executive Order 13563, 

issued after the working group developed the 2010 social cost of carbon estimates, 

commits the administration to regulatory decision making based on the best available 

science. 

21GAO, Standards for Internal Control in the Federal Government, GAO/AIMD-00-21.3.1

(Washington, D.C.: November 1999). 

22GAO, GAO-11-317; Managing for Results: Key Considerations for Implementing 

Interagency Collaborative Mechanisms, GAO-12-1022 (Washington, D.C.: Sept. 27, 

2012); and Managing for Results: Implementation Approaches Used to Enhance 

Collaboration in Interagency Groups, GAO-14-220 (Washington, D.C.: Feb. 14, 2014). 

23GAO-12-1022. 
Page 12 GAO-14-663 Social Cost of Carbon

Participants told us that the working group’s processes and methods 

reflected three key principles. First, the group used consensus-based 

decision making. Second, the group relied largely on existing academic 

literature and models, including technical assistance from outside 

resources. Third, the group took steps to disclose limitations and 

incorporate new information by considering public comments and revising 

the estimates as updated research became available.

All of the participants we spoke with said that the working group used a 

consensus-based approach for making key decisions on developing the 

social cost of carbon estimates. Most participants said that the working 

group’s overall approach was open and collegial, and that participants 

had many opportunities to make contributions and raise issues for 

discussion that were important to them.

OMB staff stated that the working group did not assign roles or 

responsibilities, and many participants told us that different working group 

participants and agencies volunteered to take responsibility for various 

aspects of the development of the estimates that fell within their particular 

areas of expertise. For example, OMB staff stated that, while OMB and 

the Council of Economic Advisers were the official leaders of the working 

group meetings, all EOP offices that participated played a large role 

during the meetings, and discussions were informal. According to these 

staff and other officials we spoke with, participants could generally 

choose the extent of their involvement, and all participants’ contributions 

were considered equally.

According to many participants, the Council of Economic Advisers 

coordinated drafting the Technical Support Document, including gathering 

feedback from working group members. Specifically, they told us that, 

following the meetings, officials from the Council of Economic Advisers 

summarized the group discussions to include in the latest draft of the 

Technical Support Document and circulated draft sections of the 

Technical Support Document for the working group to review. For 

example, a participant told us that he raised concerns about whether the 

Technical Support Document provided adequate information on domestic 

measures of the social cost of carbon. The participant said that, in 

response to this feedback, the working group decided to include a 

separate discussion in the Technical Support Document on estimating 

domestic benefits and costs. The Technical Support Document states that 

reported domestic effects should be calculated using a range of values 

from 7 to 23 percent of the global measure of the social cost of carbon, 

although it cautions that these values are approximate, provisional, and 

Processes and Methods

Used Consensus-Based 

Decision Making
Page 13 GAO-14-663 Social Cost of Carbon

highly speculative due to limited evidence. None of the participants we 

spoke with expressed concerns about how their contributions were 

incorporated into the final Technical Support Document. The participants 

generally stated that they were satisfied that the final Technical Support 

Document successfully addressed individual comments on the draft 

version and the overall consensus of the working group and its 

participating offices and agencies.

The Technical Support Document states that the main objective of the 

working group was to develop a range of estimates of the social cost of 

carbon using a defensible set of modeling inputs based on existing 

academic literature. Many participants confirmed that the working group 

relied largely on existing academic literature and models to develop its 

estimates. According to the Technical Support Document and many 

participants we spoke with, the working group calculated its estimates 

using three models that integrate climate and economic data into a single 

modeling framework for estimating future economic effects resulting from 

climate change.24 In general, each model translates carbon dioxide 

emissions scenarios into changes in greenhouse gas concentrations in 

the atmosphere, greenhouse gas concentrations in the atmosphere into 

temperature changes, and temperature changes into net economic 

effects (i.e., damages and benefits). However, each model uses its own 

methods to estimate these effects. The Technical Support Document 

states that the three models are frequently cited in peer-reviewed 

literature. They have also been used in climate assessments by the 

Intergovernmental Panel on Climate Change—an organization within the 

United Nations that assesses scientific, technical, and economic 

information on the effects of climate change. In addition, the National 

Research Council of the National Academies recognized these three 

models as three of the most widely used models of their kind.25

Many participants told us that the working group spent most of its meeting 

time reviewing and discussing academic literature to help decide on 

 24The three models are Dynamic Integrated Climate and Economy (DICE), Climate 

Framework for Uncertainty, Negotiation, and Distribution (FUND), and Policy Analysis of 

the Greenhouse Effect (PAGE). They were first developed in the early 1990s by 

researchers acknowledged as leaders in their field and are updated regularly based on 

new developments in climate and economic research. 

25National Research Council, Hidden Costs of Energy: Unpriced Consequences of Energy 

Production and Use (Washington, D.C.: National Academies Press, 2010). 

Relied on Existing Academic 

Literature and Models
Page 14 GAO-14-663 Social Cost of Carbon

values for three key modeling inputs to run in each model. The key 

modeling inputs the working group selected were based on data from 

prevalent research organizations, such as the Stanford Energy Modeling 

Forum, and reflected the wide uncertainty in the academic literature, 

according to the Technical Support Document.26 These inputs were as 

follows:

• scenarios for future population and economic growth (i.e., gross 

domestic product) and carbon dioxide emissions,

• a measure of the climate’s responsiveness to increased 

concentrations of greenhouse gases in the atmosphere—known as 

equilibrium climate sensitivity,27 and

• discount rates.

Several participants told us that different meetings focused on different 

modeling inputs and included technical presentations by participants with 

expertise in each technical area. For example, due to their previous 

experience working with the models, EPA officials made presentations on 

how each model works. OMB staff stated that the technical presentations 

focused on the academic materials cited in the Technical Support 

Document, including dozens of peer-reviewed journal articles. They also 

said that all technical decisions discussed in the Technical Support 

Document were arrived at by consensus through this process. Several 

participants said that a significant amount of the group’s discussions 

focused on selecting discount rates that best reflect the most current 

academic literature, while also comporting with OMB’s guidance in 

Circular A-4. The Technical Support Document cites guidance from 

Circular A-4 in its discussion of many technical topics, including its 

selection of discount rates. It states that the discount rate (i.e., 3 percent) 

used to calculate the central value of the social cost of carbon estimates 

is consistent with Circular A-4 guidance. Some working group participants 

told us that they recognized the importance of using OMB guidance, 

including Circular A-4, in developing the Technical Support Document. 

The Technical Support Document states that the working group decided 

 26The Stanford Energy Modeling Forum is an international forum for sharing and 

facilitating discussions on energy policy and global climate issues among researchers. 

27Equilibrium climate sensitivity is the long-term increase in the annual global-average 

surface temperature from a sustained doubling of the concentration of carbon dioxide in 

the atmosphere relative to preindustrial levels of the concentration of carbon dioxide in the 

atmosphere. 
Page 15 GAO-14-663 Social Cost of Carbon

to calculate estimates for several discount rates (2.5, 3, and 5 percent) 

because the academic literature shows that the social cost of carbon is 

highly sensitive to the discount rate chosen, and because no consensus 

exists on the appropriate rate. It further states that, in light of such 

uncertainties, the working group determined that these three discount 

rates reflect reasonable judgments about the appropriate rate to use. 

Several participants stated that the working group chose this approach to 

capture varied concerns and interests, including participants’ respective 

knowledge of the academic literature, on selecting the discount rate.

Once the working group agreed on these modeling inputs, EPA officials 

supervised their use in running the models to calculate the social cost of 

carbon estimates. All other model assumptions and features were 

unchanged by the working group, which weighted each model equally to 

calculate the final estimates. Several participants stated that an important 

principle for the leaders of the working group was that the working group 

reach consensus on the modeling inputs before running the models and 

agree, in advance, to accept the results based on the inputs selected, 

whatever the outcome. Through this approach, the working group 

developed a set of four social cost of carbon estimates for use in 

regulatory impact analyses. The first three values are based on the 

average of the estimates produced by all three models and selected 

modeling inputs at the three discount rates chosen. The fourth value was 

included to represent higher-than-expected economic impacts from 

climate change, and it is based on an average of certain values produced 

by each model at a 3 percent discount rate.28 To capture uncertainties 

involved in regulatory impact analysis, the Technical Support Document 

emphasizes the importance of agencies considering all four estimates 

when conducting analyses.

According to EPA documentation and several participants, groups from 

outside the federal government did not participate in the working group, 

but the working group used some outside resources, specifically technical 

assistance. As noted in the Technical Support Document, the working 

group explored technical literature in relevant fields for developing the 

social cost of carbon estimates. Members of the working group 

 28According to the Technical Support Document, the working group determined the fourth 

value by combining the values appearing at the furthest reaches of the distributions 

produced by each model. For this purpose, the working group used values produced from 

all three models for the 95th percentile at a 3 percent discount rate. 
Page 16 GAO-14-663 Social Cost of Carbon

sometimes contacted researchers or developers of key data in an effort to 

ensure that the working group had a clear understanding of the 

information and how to use it. For example, according to several 

participants, members of the working group consulted with lead authors of 

a chapter on climate sensitivity that appears in the Fourth Assessment 

Report of the Intergovernmental Panel on Climate Change.

29 According to 

the Technical Support Document, after consulting with the chapter 

authors, the working group was able to make some decisions to assist 

with statistical analyses needed to develop the social cost of carbon 

estimates. Many participants stated that the working group also consulted 

with the developers of the models used by the group to develop the 

estimates. For example, EPA officials told us that, while they conducted 

runs for one model that was readily available to the public, they spent a 

few days training with the developer of a second model before using it to 

conduct runs. They also contracted with the developer of a third model to 

run the model according to the decisions reached by the working group. 

They stated that they ran all of the 2013 estimates themselves, but that 

they continued to consult with the model developers to do so.

According to many participants and the 2013 update to the Technical 

Support Document, the only changes made to the models used for the 

2013 revisions were those that the model developers incorporated into 

the latest versions of the models and that were subsequently used in 

peer-reviewed academic literature. Specifically, the developers updated 

the academic models to reflect new scientific information, such as in sea 

level rise and associated damages, resulting in higher estimates.30 The 

working group did not make changes in the modeling inputs that it used 

 29Intergovernmental Panel on Climate Change, Climate Change 2007: The Physical 

Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the 

Intergovernmental Panel on Climate Change (S. Solomon, et al. [eds.])(Cambridge, UK: 

Cambridge University Press, 2007). 

30This new scientific information included an explicit representation of sea level rise and 

associated damages, updated climate change adaptation assumptions, and updated 

damage functions for agricultural impacts. 
Page 17 GAO-14-663 Social Cost of Carbon

for the 2010 estimates.31 Several participants said that, while the original 

working group included frequent, hours-long meetings over several 

months, the working group assembled to discuss the 2013 revisions only 

met a few times. According to the 2010 Technical Support Document, the 

working group is committed to updating its estimates as the science and 

economic understanding of climate change and its impacts on society 

improve over time.

According to several participants and the Technical Support Document, 

the working group’s processes and methods took steps to disclose 

limitations and incorporate new information by considering public 

comments and revising the estimates as updated economic and scientific 

research became available. The Technical Support Document discusses 

several limitations of its estimates and areas that the working group 

identified as being in particular need of additional exploration and 

research. For example, it points out that none of the three models 

accounts for damages from wildlife loss or ocean acidification caused by 

carbon dioxide emissions. Also, the models cannot completely predict 

how technology may adapt to warmer temperatures. In addition, 

according to the Technical Support Document, the models may not fully 

consider the effects of damages due to potential catastrophic events, 

such as the melting of Antarctic ice sheets. As a result of such limitations, 

the models may underestimate damages from increased carbon 

emissions, according to the Technical Support Document. The Technical 

Support Document states that, as a result of these limitations, the social 

cost of carbon estimates should continue to evolve as knowledge is 

gained, and available models improve. Some of the participating agencies 

have incorporated discussions of these limitations into regulatory impact 

analyses using social cost of carbon estimates. For example, in a 2012 

rule setting pollution standards for certain power plants, EPA noted that 

 31In January 2014, a former coleader of the working group discussed some of the reasons 

behind this approach in a presentation before the annual meeting of the American 

Economic Association, a leading economic interest group. See Cass Sunstein, “On Not 

Revisiting Official Discount Rates: Institutional Inertia and the Social Cost of Carbon”

(paper presented at the annual meeting of the American Economic Association, 

Philadelphia, PA, Jan. 3, 2014). In 2013, another former coleader of the working group 

published a paper detailing the working group’s methodology. See Greenstone, Michael et 

al., “Developing a Social Cost of Carbon for U.S. Regulatory Analysis: A Methodology and 

Interpretation,” Review of Environmental Economics and Policy 7, no. 1: 23-46 (2013). 

Took Steps to Disclose 

Limitations and Incorporate 

New Information
Page 18 GAO-14-663 Social Cost of Carbon

the social cost of carbon estimates are subject to limitations and 

uncertainties.32

Over the years, there have been opportunities for public comment on the 

various individually developed and working group estimates of the social 

cost of carbon for regulatory impact analysis, and several participants 

stated that these estimates were developed with input from the public. 

Since 2008, agencies have published over three dozen regulatory actions 

for public comment in the Federal Register that use various social cost of 

carbon estimates in regulatory impact analyses. While some of them 

specifically sought comments on the development of the social cost of 

carbon estimates used, and others did not, these regulatory actions were 

open to public comment, in general, for approximately 60 days and, 

according to OMB staff and other participants, agencies received many 

comments on the estimates through this process. Several participants 

stated that, while they discussed such public comments during working 

group meetings, individual agencies typically do not coordinate formally 

with other agencies on their reviews of comments received. According to 

the Technical Support Document, the working group convened, in part, to 

consider public comments on issues related to the social cost of carbon. 

After considering public comments on the interim values that agencies 

used in several rules, the working group developed the Technical Support 

Document, according to these participants and to the Technical Support 

Document. Several participants told us that the working group decided to 

revise the estimates for the first time in 2013 after agencies received a 

number of public comments encouraging revisions because the models 

used to develop the 2010 estimates had been subsequently updated and 

used in peer-reviewed academic literature. OMB staff stated that this 

theme was reflected in several public comments on regulations using the 

2010 estimates.

In November 2013, OMB published a request in the Federal Register for 

public comments on all aspects of the Technical Support Document and 

 32National Emission Standards for Hazardous Air Pollutants From Coal- and Oil-Fired 

Electric Utility Steam Generating Units and Standards of Performance for Fossil-FuelFired Electric Utility, Industrial-Commercial-Institutional, and Small Industrial-CommercialInstitutional Steam Generating Units, 77 Fed. Reg. 9304 (Feb. 16, 2012). 
Page 19 GAO-14-663 Social Cost of Carbon

its use of the models to develop estimates of the social cost of carbon.33

The notice stated that OMB is particularly interested in comments on the 

selection of the models for use in developing the estimates, how the 

distribution of estimates should be represented in regulatory impact 

analyses, and the strengths and limitations of the overall approach. OMB 

staff told us that they decided to issue the request in response to calls for 

additional transparency, and that they received over 100 unique 

comments and thousands of identical form-letter comments in response 

to the request. They said that, since they were still reviewing the 

comments received, they had not yet decided on steps for responding to 

them, but that they expect to review them with the working group to 

determine whether they could inform future updates to the Technical 

Support Document. OMB staff stated that they have already made most 

of the comments publicly available online at http://www.regulations.gov/

and that all of the comments would be made available soon.

The Technical Support Document states that the working group would 

regularly revisit the social cost of carbon estimates as new information 

becomes available due to improved scientific and economic research. 

The Technical Support Document set a goal of revisiting the estimates 

within 2 years, or when substantially updated models become available. 

Many participants told us that, to revise the estimates in 2013, the 

working group met only a few times and mostly for participants from EPA 

to present information about updates made to the models since the group 

last met in 2010. The updates touched on a variety of issues, including 

how some models represent damages from sea level rise. The 2013 

update to the Technical Support Document states that it acknowledges 

the continued limitations described in the original Technical Support 

Document, and that it updates the estimates based on new versions of 

the underlying models without revisiting the working group’s decisions on 

modeling inputs. Several participants stated that they reviewed drafts of 

the 2013 update to the Technical Support Document, but that there was 

little new information to review because only the models had been 

updated. In addition to stating that the working group would regularly 

 33Technical Support Document: Technical Update of the Social Cost of Carbon for 

Regulatory Impact Analysis under Executive Order No. 12866, 78 Fed. Reg. 70,586 (Nov. 

26, 2013). In January 2014, OMB extended the public comment period through February 

26, 2014. See Technical Support Document: Technical Update of the Social Cost of 

Carbon for Regulatory Impact Analysis Under Executive Order No. 12866, 79 Fed. Reg. 

4359 (Jan. 27, 2014). 
Page 20 GAO-14-663 Social Cost of Carbon

revisit its estimates, the Technical Support Document states that the 

working group will continue to support research to improve the estimates 

and hopes to develop methods to value other greenhouse gases as part 

of its ongoing work.34

We provided a draft of this report for review and comment to the 

Departments of Agriculture, Commerce, Energy, Transportation, and the 

Treasury; EPA; and OMB. Only the Department of the Treasury provided 

written comments, which we received on July 14, 2014, and are 

reproduced in appendix II; in its written comments, the Department of the 

Treasury stated that the draft report does a good job of capturing the 

interagency process through which the estimates of the social cost of 

carbon were developed. In oral comments provided on July 15, 2014, 

OMB staff confirmed that OMB generally agreed with the report findings. 

OMB staff also provided technical comments, which we incorporated into 

the report, as appropriate. The Department of Energy and EPA provided 

technical comments only, which we incorporated into the report, as 

appropriate. In e-mails received on July 1, July 9, and July 14, 2014, 

respectively, the liaisons from the Departments of Agriculture, Commerce, 

and Transportation stated that the departments did not have any 

comments on the draft report.

As agreed with your offices, unless you publicly announce the contents of 

this report earlier, we plan no further distribution until 30 days from the 

report date. At that time, we will send copies to the appropriate 

congressional committees; the Secretaries of Agriculture, Commerce, 

Energy, Transportation, and the Treasury; the Administrator of EPA; the 

 34In late 2010 and early 2011, EPA and the Department of Energy sponsored two 

workshops on valuing climate change damages for regulatory analysis. The agencies 

reported that they sponsored the workshops to prepare for and inform future working 

group activities. See ICF International, Workshop Report: Improving the Assessment and 

Valuation of Climate Change Impacts for Policy and Regulatory Analysis – Part 1 (January 

2011); summary of workshop sponsored by EPA and the Department of Energy and titled 

“Modeling Climate Change Impacts and Associated Economic Damages” (Washington, 

D.C.: Nov. 18-19, 2010) and Workshop Report: Improving the Assessment and Valuation 

of Climate Change Impacts for Policy and Regulatory Analysis – Part 2 (March 2011); 

summary of workshop sponsored by EPA and the Department of Energy and titled 

“Research on Climate Change Impacts and Associated Economic Damages”

(Washington, D.C., Jan. 27-28, 2011). 

Agency Comments
Page 21 GAO-14-663 Social Cost of Carbon

Director of OMB; and other interested parties. In addition, the report will 

be available at no charge on the GAO website at http://www.gao.gov.

If you or your staff members have any questions about this report, please 

contact me at (202) 512-3841 or gomezj@gao.gov. Contact points for our 

Offices of Congressional Relations and Public Affairs may be found on 

the last page of this report. Key contributors to this report are listed in 

appendix III.

J. Alfredo Gómez

Director, Natural Resources and Environment
Appendix I: Regulatory Actions, by Agency 

and Type of Social Cost of Carbon Estimates 

Used, 2008-2014

Page 22 GAO-14-663 Social Cost of Carbon

This appendix lists regulatory actions from 2008 to 2014 and the type of 

social cost of carbon estimates used (i.e., individually developed, interim, 

2010, or 2013) in the actions’ regulatory impact analyses. For each 

regulatory action, table 3 lists the date published in the Federal Register, 

the agency conducting the action, the name and status of the rule 

associated with the action, and the action’s citation in the Federal 

Register.

Table 3: Regulatory Actions, by Agency and Type of Social Cost of Carbon Estimates Used in the Regulatory Impact Analysis, 

2008-2014

Date published in the 

Federal Register Agency Rule Status of rule

Federal 

Register

citation

Individually developed agency estimates

May 2, 2008 Department of 

Transportation 

(Transportation), National 

Highway Traffic Safety 

Administration (NHTSA)

Average Fuel Economy Standards, 

Passenger Cars and Light Trucks; 

Model Years 2011-2015 

Proposed 73 Fed. Reg. 

24,352

July 30, 2008 Environmental Protection 

Agency (EPA)

Regulating Greenhouse Gas 

Emissions Under the Clean Air Act

Advanced Notice of 

Proposed 

Rulemaking

73 Fed. Reg. 

44,354

Aug. 25, 2008 Department of Energy 

(Energy)

Energy Conservation Program for 

Commercial and Industrial 

Equipment: Energy Conservation 

Standards for Commercial IceCream Freezers; Self-Contained 

Commercial Refrigerators, 

Commercial Freezers, and 

Commercial Refrigerator-Freezers 

Without Doors; and Remote 

Condensing Commercial 

Refrigerators, Commercial Freezers, 

and Commercial RefrigeratorFreezers

Proposed 73 Fed. Reg. 

50,072

Oct. 7, 2008 Energy Energy Conservation Program for 

Commercial and Industrial 

Equipment: Packaged Terminal Air 

Conditioner and Packaged Terminal 

Heat Pump Energy Conservation 

Standards

Final 73 Fed. Reg. 

58,772

Appendix I: Regulatory Actions, by Agency 

and Type of Social Cost of Carbon Estimates 

Used, 2008-2014
Appendix I: Regulatory Actions, by Agency 

and Type of Social Cost of Carbon Estimates 

Used, 2008-2014

Page 23 GAO-14-663 Social Cost of Carbon

Date published in the 

Federal Register Agency Rule Status of rule

Federal 

Register

citation

Oct. 17, 2008 Energy Energy Conservation Program: 

Energy Conservation Standards for 

Certain Consumer Products 

(Dishwashers, Dehumidifiers, 

Electric and Gas Kitchen Ranges 

and Ovens, and Microwave Ovens) 

and for Certain Commercial and 

Industrial Equipment (Commercial 

Clothes Washers)

Proposed 73 Fed. Reg. 

62,034

Jan. 9, 2009 Energy Energy Conservation Program for 

Commercial and Industrial 

Equipment: Energy Conservation 

Standards for Commercial IceCream Freezers; Self-Contained 

Commercial Refrigerators, 

Commercial Freezers, and 

Commercial Refrigerator-Freezers 

Without Doors; and Remote 

Condensing Commercial 

Refrigerators, Commercial Freezers, 

and Commercial RefrigeratorFreezers

Final 74 Fed. Reg. 

1092

Mar. 30, 2009 Transportation, NHTSA Average Fuel Economy Standards 

Passenger Cars and Light Trucks 

Model Year 2011

Final 74 Fed. Reg. 

14,196

Apr. 8, 2009 Energy Energy Conservation Program: 

Energy Conservation Standards for 

Certain Consumer Products 

(Dishwashers, Dehumidifiers, 

Microwave Ovens, and Electric and 

Gas Kitchen Ranges and Ovens) 

and for Certain Commercial and 

Industrial Equipment (Commercial 

Clothes Washers)

Final 74 Fed. Reg. 

16,040

Apr. 13, 2009 Energy Energy Conservation Program: 

Energy Conservation Standards for 

General Service Fluorescent Lamps 

and Incandescent Reflector Lamps

Proposed 74 Fed. Reg. 

16,920

May 26, 2009 EPA Regulation of Fuels and Fuel 

Additives: Changes to Renewable 

Fuel Standard Program

Proposed 74 Fed. Reg. 

24,904

May 29, 2009 Energy Energy Conservation Program: 

Energy Conservation Standards for 

Refrigerated Bottled or Canned 

Beverage Vending Machines

Proposed 74 Fed. Reg. 

26,020
Appendix I: Regulatory Actions, by Agency 

and Type of Social Cost of Carbon Estimates 

Used, 2008-2014

Page 24 GAO-14-663 Social Cost of Carbon

Date published in the 

Federal Register Agency Rule Status of rule

Federal 

Register

citation

July 14, 2009 Energy Energy Conservation Program: 

Energy Conservation Standards and 

Test Procedures for General Service 

Fluorescent Lamps and 

Incandescent Reflector Lamps

Final 74 Fed. Reg. 

34,080

July 22, 2009 Energy Energy Conservation Program for 

Certain Industrial Equipment: Energy 

Conservation Standards and Test 

Procedures for Commercial Heating, 

Air-Conditioning, and Water-Heating 

Equipment

Final 74 Fed. Reg. 

36,312

Interim governmentwide estimates

Aug. 31, 2009 Energy Energy Conservation Program: 

Energy Conservation Standards for 

Refrigerated Bottled or Canned 

Beverage Vending Machines

Final 74 Fed. Reg. 

44,914

Sep. 28, 2009 EPA and Transportation, 

NHTSA

Proposed Rulemaking to Establish 

Light-Duty Vehicle Greenhouse Gas 

Emission Standards and Corporate 

Average Fuel Economy Standards

Proposed 74 Fed. Reg. 

49,454

Nov. 9, 2009 Energy Energy Conservation Program: 

Energy Conservation Standards for 

Certain Consumer Products 

(Dishwashers, Dehumidifiers, 

Microwave Ovens, and Electric and 

Gas Kitchen Ranges and Ovens) 

and for Certain Commercial and 

Industrial Equipment (Commercial 

Clothes Washers)

Supplemental Notice 

of Proposed 

Rulemaking

74 Fed. Reg. 

57,738

Nov. 24, 2009 Energy Energy Conservation Program: 

Energy Conservation Standards for 

Small Electric Motors

Proposed 74 Fed. Reg. 

61,410

Dec. 11, 2009 Energy Energy Conservation Program: 

Energy Conservation Standards for 

Residential Water Heaters, Direct 

Heating Equipment, and Pool 

Heaters

Proposed 74 Fed. Reg. 

65,852

Jan. 8, 2010 Energy Energy Conservation Program: 

Energy Conservation Standards for 

Certain Consumer Products 

(Dishwashers, Dehumidifiers, 

Microwave Ovens, and Electric and 

Gas Kitchen Ranges and Ovens) 

and for Certain Commercial and 

Industrial Equipment (Commercial 

Clothes Washers)

Final 75 Fed. Reg. 

1122
Appendix I: Regulatory Actions, by Agency 

and Type of Social Cost of Carbon Estimates 

Used, 2008-2014

Page 25 GAO-14-663 Social Cost of Carbon

Date published in the 

Federal Register Agency Rule Status of rule

Federal 

Register

citation

Mar. 26, 2010 EPA Regulation of Fuels and Fuel 

Additives: Changes to Renewable 

Fuel Standard Program

Final 75 Fed. Reg. 

14,670

June 21, 2010 EPA Hazardous and Solid Waste 

Management System; Identification 

and Listing of Special Wastes; 

Disposal of Coal Combustion 

Residuals From Electric Utilities

Proposed 75 Fed. Reg. 

35,128

2010 governmentwide estimates

Mar. 9, 2010 Energy Energy Conservation Program: 

Energy Conservation Standards for 

Small Electric Motors

Final 75 Fed. Reg. 

10,874

Apr. 16, 2010 Energy Energy Conservation Program: 

Energy Conservation Standards for 

Residential Water Heaters, Direct 

Heating Equipment, and Pool 

Heaters

Final 75 Fed. Reg. 

20,112

May 7, 2010 EPA and Transportation, 

NHTSA

Light Duty Vehicle Greenhouse Gas 

Emission Standards and Corporate 

Average Fuel Economy Standards

Final 75 Fed. Reg. 

25,324

May 28, 2010 Transportation, Federal 

Aviation Administration

Automatic Dependent Surveillance—

Broadcast (ADS-B) Out 

Performance Requirements to 

Support Air Traffic Control (ATC) 

Service

Final 75 Fed. Reg. 

30,160

Aug. 2, 2010 EPA Federal Implementation Plans To 

Reduce Interstate Transport of Fine 

Particulate Matter and Ozone

Proposed 75 Fed. Reg. 

45,210

Sep. 9, 2010 EPA National Emission Standards for 

Hazardous Air Pollutants from the 

Portland Cement Manufacturing 

Industry and Standards of 

Performance for Portland Cement 

Plants

Final 75 Fed. Reg. 

54,970

Oct. 14, 2010 EPA Standards of Performance for New

Stationary Sources and Emission 

Guidelines for Existing Sources: 

Sewage Sludge Incineration Units

Proposed 75 Fed. Reg. 

63,260

Nov. 30, 2010 EPA and Transportation, 

NHTSA

Greenhouse Gas Emissions 

Standards and Fuel Efficiency 

Standards for Medium- and HeavyDuty Engines and Vehicles

Proposed 75 Fed. Reg. 

74,152
Appendix I: Regulatory Actions, by Agency 

and Type of Social Cost of Carbon Estimates 

Used, 2008-2014

Page 26 GAO-14-663 Social Cost of Carbon

Date published in the 

Federal Register Agency Rule Status of rule

Federal 

Register

citation

Mar. 14, 2011 EPA National Emission Standards for 

Hazardous Air Pollutants: Mercury 

Emissions from Mercury Cell ChlorAlkali Plants

Supplemental 

Proposed Rule

76 Fed. Reg. 

13,852

Mar. 21, 2011 EPA Standards of Performance for New 

Stationary Sources and Emission 

Guidelines for Existing Sources: 

Sewage Sludge Incineration Units

Final 76 Fed. Reg. 

15,372

Mar. 21, 2011 EPA National Emission Standards for 

Hazardous Air Pollutants for Major 

Sources: Industrial, Commercial, 

and Institutional Boilers and Process 

Heaters

Final 76 Fed. Reg. 

15,608

Apr. 11, 2011 Energy Energy Conservation Program: 

Energy Conservation Standards for 

Fluorescent Lamp Ballasts

Proposed 76 Fed. Reg. 

20,090

Apr. 21, 2011 Energy Energy Conservation Program: 

Energy Conservation Standards for 

Residential Clothes Dryers and 

Room Air Conditioners

Direct Final 76 Fed. Reg. 

22,454

June 27, 2011 Energy Energy Conservation Program: 

Energy Conservation Standards for 

Residential Furnaces and 

Residential Central Air Conditioners 

and Heat Pumps

Direct Final 76 Fed. Reg. 

37,408

Aug. 8, 2011 EPA Federal Implementation Plans: 

Interstate Transport of Fine 

Particulate Matter and Ozone and 

Correction of SIP Approvals

Final

a

76 Fed. Reg. 

48,208

Sep. 15, 2011 EPA and Transportation, 

NHTSA

Greenhouse Gas Emissions 

Standards and Fuel Efficiency 

Standards for Medium- and HeavyDuty Engines and Vehicles

Final 76 Fed. Reg. 

57,106

Sep. 15, 2011 Energy Energy Conservation Program: 

Energy Conservation Standards for 

Residential Refrigerators, 

Refrigerator-Freezers, and Freezers

Final 76 Fed. Reg. 

57,516

Nov. 14, 2011 Energy Energy Conservation Program: 

Energy Conservation Standards for 

Fluorescent Lamp Ballasts

Final 76 Fed. Reg. 

70,548

Dec. 1, 2011 EPA and Transportation, 

NHTSA

2017 and Later Model Year LightDuty Vehicle Greenhouse Gas 

Emissions and Corporate Average 

Fuel Economy Standards

Proposed 76 Fed. Reg. 

74,854
Appendix I: Regulatory Actions, by Agency 

and Type of Social Cost of Carbon Estimates 

Used, 2008-2014

Page 27 GAO-14-663 Social Cost of Carbon

Date published in the 

Federal Register Agency Rule Status of rule

Federal 

Register

citation

Dec. 23, 2011 EPA Commercial and Industrial Solid 

Waste Incineration Units: 

Reconsideration and Proposed 

Amendments; Non-Hazardous 

Secondary Materials That Are Solid 

Waste

Proposed 76 Fed. Reg. 

80,452

Jan. 17, 2012 Energy Energy Conservation Program for 

Certain Industrial Equipment: Energy 

Conservation Standards and Test 

Procedures for Commercial Heating, 

Air-Conditioning, and Water-Heating 

Equipment

Proposed 77 Fed. Reg. 

2356

Feb. 10, 2012 Energy Energy Conservation Program: 

Energy Conservation Standards for 

Distribution Transformers

Proposed 77 Fed. Reg. 

7282

Feb. 14, 2012 Energy Energy Conservation Program: 

Energy Conservation Standards for 

Standby Mode and Off Mode for 

Microwaves

Supplemental Notice 

of Proposed 

Rulemaking

77 Fed. Reg. 

8526

Feb. 16, 2012 EPA National Emission Standards for 

Hazardous Air Pollutants from Coaland Oil-Fired Electric Utility Steam 

Generating Units and Standards of 

Performance for Fossil-Fuel-Fired 

Electric Utility, IndustrialCommercial-Institutional, and Small 

Industrial-Commercial-Institutional 

Steam Generating Units

Final 77 Fed. Reg.

9304

Mar. 27, 2012 Energy Energy Conservation Program: 

Energy Conservation Standards for 

Battery Chargers and External 

Power Supplies

Proposed 77 Fed. Reg. 

18,478

Apr. 13, 2012 EPA Standards of Performance for 

Greenhouse Gas Emissions for New 

Stationary Sources: Electric Utility 

Generating Units

Proposed 77 Fed. Reg. 

22,392

May 30, 2012 Energy Energy Conservation Program: 

Energy Conservation Standards for 

Residential Dishwashers

Direct Final 77 Fed. Reg. 

31,918

May 31, 2012 Energy Energy Conservation Program: 

Energy Conservation Standards for 

Residential Clothes Washers

Direct Final 77 Fed. Reg. 

32,308

Oct. 15, 2012 EPA and Transportation, 

NHTSA

2017 and Later Model Year LightDuty Vehicle Greenhouse Gas 

Emissions and Corporate Average 

Fuel Economy Standards

Final 77 Fed. Reg. 

62,624
Appendix I: Regulatory Actions, by Agency 

and Type of Social Cost of Carbon Estimates 

Used, 2008-2014

Page 28 GAO-14-663 Social Cost of Carbon

Date published in the 

Federal Register Agency Rule Status of rule

Federal 

Register

citation

Apr. 18, 2013 Energy Energy Conservation Program: 

Energy Conservation Standards for 

Distribution Transformers

Final 78 Fed. Reg. 

23,336

June 7, 2013 EPA Effluent Limitations Guidelines and 

Standards for the Steam Electric 

Power Generating Point Source 

Category

Proposed 78 Fed. Reg. 

34,432

2013 revised governmentwide estimates

June 17, 2013 Energy Energy Conservation Program: 

Energy Conservation Standards for 

Standby Mode and Off Mode for 

Microwave Ovens

Final 78 Fed. Reg. 

36,316

Aug. 20, 2013 Energy Energy Conservation Program: 

Energy Conservation Standards for 

Metal Halide Lamp Fixtures

Proposed 78 Fed. Reg. 

51,464

Sep. 11, 2013 Energy Energy Conservation Program: 

Energy Conservation Standards for 

Walk-In Coolers and Freezers

Proposed 78 Fed. Reg. 

55,782

Sep. 11, 2013 Energy Energy Conservation Program: 

Energy Conservation Standards for 

Commercial Refrigeration 

Equipment

Proposed 78 Fed. Reg. 

55,890

Oct. 25, 2013 Energy Energy Conservation Program for 

Consumer Products: Energy 

Conservation Standards for 

Residential Furnace Fans

Proposed 78 Fed. Reg. 

64,068

Dec. 6, 2013 Energy Energy Conservation Program: 

Energy Conservation Standards for 

Commercial and Industrial Electric 

Motors

Proposed 78 Fed. Reg. 

73,590

Jan. 8, 2014 EPA Standards of Performance for 

Greenhouse Gas Emissions from 

New Stationary Sources: Electric 

Utility Generating Units

Proposed 79 Fed. Reg. 

1430

Feb. 10, 2014 Energy Energy Conservation Program: 

Energy Conservation Standards for 

Metal Halide Lamp Fixtures

Final 79 Fed. Reg. 

7746

Feb. 10, 2014 Energy Energy Conservation Program: 

Energy Conservation Standards for 

External Power Supplies

Final 79 Fed. Reg. 

7846

Mar. 4, 2014 Energy Energy Conservation Program: 

Energy Conservation Standards for 

Commercial Clothes Washers

Proposed 79 Fed. Reg. 

12,302
Appendix I: Regulatory Actions, by Agency 

and Type of Social Cost of Carbon Estimates 

Used, 2008-2014

Page 29 GAO-14-663 Social Cost of Carbon

Date published in the 

Federal Register Agency Rule Status of rule

Federal 

Register

citation

Mar. 17, 2014 Energy Energy Conservation Program: 

Energy Conservation Standards for 

Automatic Commercial Ice Makers

Proposed 79 Fed. Reg. 

14,846

Mar. 28, 2014 Energy Energy Conservation Program: 

Energy Conservation Standards for 

Commercial Refrigeration 

Equipment

Final 79 Fed. Reg. 

17,726

Apr. 29, 2014 Energy Energy Conservation Program: 

Energy Conservation Standards for 

General Service Fluorescent Lamps 

and Incandescent Reflector Lamps

Proposed 79 Fed. Reg. 

24,068

May 29, 2014 Energy Energy Conservation Program: 

Energy Conservation Standards for 

Commercial and Industrial Electric 

Motors

Final 79 Fed. Reg. 

30,934

June 3, 2014 Energy Energy Conservation Program: 

Energy Conservation Standards for 

Walk-In Coolers and Freezers

Final 79 Fed. Reg. 

32,050

June 18, 2014 EPA Carbon Pollution Emission 

Guidelines for Existing Stationary 

Sources: Electric Utility Generating 

Units

Proposed 79 Fed. Reg. 

34,830

Sources: Environmental Protection Agency and Federal Register. | GAO-14-663

Notes:

Regulatory actions in this table are as of June 18, 2014.

In 2008 and early 2009, individual estimates of the social cost of carbon were developed by each 

agency and typically based on estimates published in academic literature. The interim 

governmentwide estimates were developed in early 2009 by the Interagency Working Group on 

Social Cost of Carbon and derived from an average of selected estimates published in academic 

literature. The 2010 governmentwide estimates were developed by the Interagency Working Group 

on Social Cost of Carbon and issued in its February 2010 Technical Support Document. The 2013 

revised governmentwide estimates were developed by the Interagency Working Group on Social Cost 

of Carbon and issued in a May 2013 update to the Technical Support Document, which was reissued 

with minor technical corrections in November 2013. 

a

SIP refers to State Implementation Plan.
Appendix II: Comments from the Department 

of the Treasury

Page 30 GAO-14-663 Social Cost of Carbon

Appendix II: Comments from the Department 

of the Treasury
Appendix III: GAO Contact and Staff 

Acknowledgments

Page 31 GAO-14-663 Social Cost of Carbon

J. Alfredo Gómez, (202) 512-3841, or gomezj@gao.gov

In addition to the individual named above, Janet Frisch (Assistant 

Director), Elizabeth Beardsley, Stephanie Gaines, Cindy Gilbert, Chad M. 

Gorman, Tim Guinane, Patricia Moye, Susan Offutt, Alison O’Neill, and 

Kiki Theodoropoulos made key contributions to this report.

Appendix III: GAO Contact and Staff 

Acknowledgments

GAO Contact

Staff 

Acknowledgments

(361544)
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