United States Court of Appeals

FOR THE DISTRICT OF COLUMBIA CIRCUIT

Argued April 8, 2005 Decided July 15, 2005

Reissued September 13, 2005

No. 03-1361

COMMONWEALTH OF MASSACHUSETTS, ET AL.,

PETITIONERS

v.

ENVIRONMENTAL PROTECTION AGENCY,

RESPONDENT

ALLIANCE OF AUTOMOBILE MANUFACTURERS, ET AL.,

INTERVENORS

Consolidated with Nos.

03-1362, 03-1363, 03-1364, 03-1365, 03-1366, 03-1367,

03-1368

On Petitions for Review of an Order of the

Environmental Protection Agency

James R. Milkey and Howard Fox argued the cause for

petitioners. With them on the briefs were Thomas F. Reilly,

Attorney General, Attorney General’s Office of the

Commonwealth of Massachusetts, William L. Pardee, Assistant

Attorney General, Joseph Mendelson, III, David Bookbinder,

Bill Lockyer, Attorney General, Attorney General’s Office of the
2

State of California, Nicholas Stern and Marc N. Melnick, Deputy

Attorneys General, David Doniger, Richard Blumenthal,

Attorney General, Attorney General’s Office of the State of

Connecticut, Kimberly Massicotte and Matthew Levine,

Assistant Attorneys General, Peter C. Harvey, Attorney General,

Attorney General’s Office of the State of New Jersey, Stefanie

A. Brand, Deputy Attorney General, Hardy Myers, Attorney

General, Attorney General’s Office of the State of Oregon,

Philip Schradle, Special Counsel, Lisa Madigan, Attorney

General, Attorney General’s Office of the State of Illinois, Gary

Feinerman, Solicitor General, Gerald T. Karr and Thomas E.

Davis, Assistant Attorneys General, Patricia A. Madrid,

Attorney General, Attorney General’s Office of the State of New

Mexico, Stuart M. Bluestone, Deputy Attorney General, Patrick

C. Lynch, Attorney General, Attorney General’s Office of the

State of Rhode Island, Tricia K. Jedele, Special Assistant, G.

Steven Rowe, Attorney General, Attorney General’s Office of

the State of Maine, Gerald D. Reid, Assistant Attorney General,

Eliot Spitzer, Attorney General, Attorney General’s Office of the

State of New York, Peter Lehner and J. Jared Snyder, Assistant

Attorneys General, William H. Sorrell, Attorney General,

Attorney General’s Office of the State of Vermont, Erick Titrud

and Kevin O. Leske, Assistant Attorneys General, Rob

McKenna, Attorney General, Attorney General’s Office of the

State of Washington, David K. Mears, Assistant Attorney

General, John Hogrogian, Assistant Corporation Counsel,

Corporation Counsel of the City of New York, Julie M.

Anderson, Fiti A. Sunia, Attorney General, Attorney General’s

Office of the American Samoa, Ralph S. Tyler, III, Solicitor,

City of Baltimore, William Phelan, Jr., Counsel, James B. Tripp,

Robert J. Spagnoletti, Attorney General, Attorney General’s

Office of the District of Columbia, Edward E. Schwab, Deputy

Attorney General, and Donna M. Murasky, Senior Litigation

Counsel.
3

Rebecca L. Bernard and Jeremy Kyle Kinner were on the

brief of amici curiae Indigenous Environmental Network,

REDOIL and Physicians for Social Responsibility. 

Jeffrey Bossert Clark, Deputy Assistant Attorney General,

U.S. Department of Justice, argued the cause for respondent.

With him on the brief were Thomas L. Sansonetti, Assistant

Attorney General, Jon M. Lipshultz, Attorney, Ann R. Klee,

General Counsel, U.S. Environmental Protection Agency, and

John T. Hannon and Nancy Ketcham-Colwill, Counsel.

Neil D. Gordon, Assistant Attorney General, Attorney

General’s Office of the State of Michigan, argued the cause for

intervenors States of Michigan, et al., and amicus curiae State

of Indiana. With him on the briefs were Alan F. Hoffman,

Assistant Attorney General, Jane E. Atwood, Assistant Attorney

General, Attorney General’s Office of the State of Texas,

Douglas Conde, Deputy Attorney General, Attorney General’s

Office of the State of Idaho, Charles M. Carvell, Assistant

Attorney General, Attorney General’s Office of the State of

North Dakota, Fred Nelson, Assistant Attorney General,

Attorney General’s Office of the State of Utah, Roxanne Giedd,

Deputy Attorney General, Attorney General’s Office of the State

of South Dakota, Steven E. Mulder, Assistant Attorney General,

Attorney General’s Office of the State of Alaska, David W.

Davies, Attorney, Attorney General’s Office of the State of

Kansas, David D. Cookson and Natalee J. Hart, Assistant

Attorneys General, Attorney General’s Office of the State of

Nebraska, Dale T. Vitale, Senior Deputy Attorney General,

Attorney General’s Office of the State of Ohio, and Thomas M.

Fisher, Special Counsel, Attorney General’s Office of the State

of Indiana.

Norman W. Fichthorn, Allison D. Wood, William A.

Anderson, II., Eric P. Gotting, Russell S. Frye, John L.
4

Wittenborn, William L. Fang, Dell E. Perelman, Leslie A. Hulse,

Richard Wasserstrom, Harry M. Ng, Ralph J. Colleli, Jr., Jan S.

Amundson, Quentin Riegel, Robin S. Conrad, John T. Whatley,

Julie C. Becker, Douglas I. Greenhaus, Jed R. Mandel, Timothy

A. French, Robert G. Slaughter, Mark J. Washko, and Nick

Goldstein were on the brief of industry intervenors in support of

respondent.

Daniel J. Popeo, Paul D. Kamenar, Peter Glaser, and

Douglas A. Henderson were on the brief of amicus curiae

Washington Legal Foundation in support of respondent.

Edward W. Warren and Eric B. Wolff were on the brief of

amicus curiae John D. Dingell (D-Michgan) in support of denial

of petitions for review.

Before: SENTELLE, RANDOLPH, and TATEL, Circuit Judges.

Judgment of the Court filed by Circuit Judge RANDOLPH.

Opinion filed by Circuit Judge RANDOLPH.

Opinion dissenting in part and concurring in the judgment

filed by Circuit Judge SENTELLE. 

Opinion dissenting in Nos. 03-1361, 03-1362, 03-1363, and

03-1364 filed by Circuit Judge TATEL.

RANDOLPH, Circuit Judge: Petitioners are twelve states,

three cities, an American territory, and numerous environmental

organizations. They are opposed by the Environmental

Protection Agency as respondent, and ten states and several

trade associations as intervenors. The controversy is about

EPA’s denial of a petition asking it to regulate carbon dioxide

(CO2) and other greenhouse gas emissions from new motor
5

vehicles under § 202(a)(1) of the Clean Air Act, 42 U.S.C.

§ 7521(a)(1). EPA concluded that it did not have statutory

authority to regulate greenhouse gas emissions from motor

vehicles and that, even if it did, it would not exercise the

authority at this time. 68 Fed. Reg. 52,922 (Sept. 8, 2003).

I.

We should say a few words about our jurisdiction under the

Clean Air Act to review an EPA denial of a petition for

rulemaking. Section 307(b)(1), 42 U.S.C. § 7607(b)(1), gives

this court exclusive jurisdiction over “nationally applicable

regulations promulgated, or final action taken, by the

Administrator” under chapter 85 of the Act. The district courts,

on the other hand, have jurisdiction over citizen suits to compel

EPA to perform nondiscretionary acts or duties. 42 U.S.C.

§ 7604(a)(2); see Sierra Club v. Thomas, 828 F.2d 783, 787-92

(D.C. Cir. 1987). Because EPA refused to promulgate

“nationally applicable regulations” after being asked to do so,

we have jurisdiction only if EPA thereby engaged in “final

action.” We can be sure that its denial of the rulemaking

petition was “final.” But did this constitute agency “action”?

To answer that question we must consult the Administrative

Procedure Act -- specifically 5 U.S.C. § 551(13). The term

“action” in § 307(b)(1) of the Clean Air Act, like the term

“final,” carries its traditional meaning in administrative law. See

Whitman v. Am. Trucking Ass’ns, 531 U.S. 457, 478 (2001);

Indep. Equip. Dealers Ass’n v. EPA, 372 F.3d 420, 428 (D.C.

Cir. 2004); Sierra Club v. Gorsuch, 715 F.2d 653, 656-57 (D.C.

Cir. 1983). Section 551(13) of the APA defines “agency action”

as “the whole or a part of an agency rule, order, license,

sanction, relief, or the equivalent or denial thereof, or failure to

act” (italics added). While § 307 of the Clean Air Act makes

several APA provisions inapplicable -- namely, 5 U.S.C. §§ 553-

557 & 706 -- APA § 551 is not among them. EPA’s denial of
6

the rulemaking petition was therefore “final action,” and since

the petition sought regulations national in scope, § 307(b)(1)

confers jurisdiction on this court to hear these consolidated

cases.

Another, related, point needs to be mentioned. Several of

the petitions for judicial review treated a memorandum of EPA’s

General Counsel, Robert Fabricant, as “final action taken, by the

Administrator” under § 307(b)(1). The memorandum, dated

August 28, 2003, and addressed to the EPA Administrator, was

entitled “EPA’s Authority to Impose Mandatory Controls to

Address Global Climate Change under the Clean Air Act.” The

General Counsel, after analyzing § 202(a)(1) of the Clean Air

Act, and other legislative and executive actions, stated his belief

that the Act “does not authorize regulation to address global

climate change.” He therefore withdrew a contrary

memorandum issued in 1998 by one of his predecessors.

The Fabricant memorandum, consisting of legal advice to

the EPA Administrator, did not in itself constitute “final action”

of the Administrator. To be sure, the Administrator adopted the

“General Counsel’s opinion” and relied on its analysis as one of

the alternative grounds for rejecting the rulemaking petition.

See 68 Fed. Reg. at 52,925. The Administrator’s explanation

incorporated many of the memorandum’s passages verbatim,

rephrased and reordered others, and expanded on the General

Counsel’s reasoning. Still, it is the Administrator’s denial of the

rulemaking petition, with the accompanying explanation, that

represents the “final action” of the Administrator subject to

judicial review under § 307(b)(1). The significance of the

General Counsel’s opinion, as set forth in his memorandum, is

the Administrator’s reliance on his reasoning in deciding the

matter now before us.
7

There is an additional jurisdictional issue presented, but not

under the Clean Air Act. EPA claims that petitioners lack

standing under Article III of the Constitution. Standing exists

only if the complainant has suffered an injury in fact, fairly

traceable to the challenged action, and likely to be redressed by

a favorable decision. See Lujan v. Defenders of Wildlife, 504

U.S. 555, 560 (1992). EPA’s argument is that petitioners have

not “adequately demonstrated” two elements of standing: that

their alleged injuries were “caused by EPA’s decision not to

regulate emissions of greenhouse gases from mobile sources”;

and that their injuries “can be redressed by a decision in their

favor” by this court. Brief for Respondent at 16.

In anticipation of this argument, petitioners filed two

volumes of declarations with the court, some containing lengthy

exhibits. The declarations, from scientists, engineers, state

officials, homeowners, users of the nation’s recreational

resources, and other individuals, predict catastrophic

consequences from global warming caused by greenhouse gases,

including loss of or damage to state and private property,

frequent intense storm surge floods, and increased health care

costs. Brief for Petitioners at 2-4.

For the causation and redressability aspects of standing,

petitioners cite two of their declarations. One, from a

climatologist, states that reductions in CO2 and other greenhouse

gases from vehicles in the United States would alone have a

meaningful impact and would “delay and moderate many of the

adverse impacts of global warming.” He adds that if EPA took

action to reduce such emissions, other countries would likely

follow suit. The climatologist bases his predictions about future

climate change on climate models and on “quantitative scenarios

generated by the IPCC” -- the Intergovernmental Panel on

Climate Change, established in 1988 by the United Nations and

the World Meteorological Organization. The other declaration
8

is from a mechanical engineer. He states that, on the basis of his

experience with controlling other pollutants, there is “no doubt

that establishing emissions standards for pollutants that

contribute to global warming would lead to investment in

developing improved technologies to reduce those emissions

from motor vehicles, and that successful technologies would

gradually be mandated by other countries around the world.”

We have held that, to establish standing, a petitioner

challenging agency action has the same burden of production as

“a plaintiff moving for summary judgment in the district court:

it must support each element of its claim to standing ‘by

affidavit or other evidence.’” Sierra Club v. EPA, 292 F.3d 895,

899 (D.C. Cir. 2002) (quoting Lujan, 504 U.S. at 561).

Petitioners’ declarations do “support each element” of standing.

But supporting an allegation is one thing; proving an allegation

is quite another. Lujan holds that when a plaintiff’s standing is

challenged in a motion for summary judgment, the plaintiff

“must ‘set forth’ by affidavit or other evidence ‘specific facts,’

Fed. Rule Civ. Proc. 56(e), which for purposes of the summary

judgment motion will be taken as true.” 504 U.S. at 561. If we

were to analogize the situation here to one in which EPA filed

such a summary judgment motion, we would conclude that

petitioners had submitted enough evidence raising genuine

issues of material fact to defeat the motion. See FED. R. CIV. P.

56©. But Lujan goes on to hold that at “the final stage” the

evidence plaintiff presented at summary judgment “(if

controverted) must be ‘supported adequately by the evidence

adduced at trial.’” 504 U.S. at 561 (quoting Gladstone, Realtors

v. Village of Bellwood, 441 U.S. 91, 115 n.31 (1979)). One

might say that in this case we are at the “final stage.” But the

analogy is not entirely apt. As an appellate court we do not

conduct evidentiary hearings in order to make findings of fact.

This is why, when Sierra Club spoke of “other evidence”

relating to standing, the court had in mind evidence presented to
9

the agency. 292 F.3d at 899. Here, the administrative record

contains a wealth of such “other evidence,” and some of it

contradicts petitioners’ claim that greenhouse gas emissions

from new motor vehicles have caused or will cause a significant

change in the global climate. That is partly why EPA decided

not to regulate at this time.

Steel Co. v. Citizens for a Better Environment, 523 U.S. 83

(1998), instructs federal courts to resolve Article III standing

questions before proceeding to the merits of a case. The

combination of Lujan, Steel Co., and the factual overlap of the

standing issues with EPA’s justifications for not regulating

greenhouse gases present us with three options. The first is to

refer the standing issues to a special master for a factual

determination. This would be, as one commentator has

suggested, “folly.” 13A CHARLES A. WRIGHT ET AL., FEDERAL

PRACTICE AND PROCEDURE 2D § 3531.15, at 101 (1984). Such

a proceeding would largely duplicate the proceedings on the

rulemaking petition and to no good end. Another option would

be to remand to EPA for a factual determination of causation

and redressability. That too would make no sense. For one

thing, judgments about standing are the responsibility of the

federal courts. For another, EPA has already reached a decision

about the state of the evidence regarding global warming from

greenhouse gases. The third option is to proceed to the merits

with respect to EPA’s alternative decision not to regulate on the

grounds, among others, that the effect of greenhouse gases on

climate is unclear and that models used to predict climate

change might not be accurate.

We have decided to follow the third course. Steel Co.

endorses this approach with respect to questions of statutory

standing. The Court explained that “the merits inquiry and the

statutory standing inquiry often overlap” and “are sometimes

identical, so that it would be exceedingly artificial to draw a
10

1

 Relying on FDA v. Brown & Williamson Tobacco Corp., 529

U.S. 120 (2000), EPA concluded that in light of the enormous

economic and political consequences of regulating greenhouse gas

emissions, Congress would have been far more specific if it had

intended to authorize EPA to regulate the subject under § 202(a)(1) of

the Clean Air Act. 58 Fed. Reg. at 52,928. We express no view on

the validity of EPA’s analysis.

distinction between the two.” 523 U.S. at 97 n.2. The Court’s

distinction of Article III standing cases rested on the premise

that there would be no such overlap and that the issue of Article

III standing would be entirely separate from the merits. Id. The

Court did not say what the proper order of decision should be

when, as in this case, that premise does not hold. In this highly

unusual circumstance -- encountered for the first time in this

court -- we will follow the statutory standing cases. We will

therefore assume arguendo that EPA has statutory authority to

regulate greenhouse gases from new motor vehicles.1 The

question we address is whether EPA properly declined to

exercise that authority.

II.

Greenhouse gases trap energy, much like the glass panels of

a greenhouse. The earth’s surface is warmed by absorbing solar

energy (visible light). The earth, in turn, radiates infrared energy

(heat) back into space. A portion of the infrared radiation is

trapped by greenhouse gas molecules, resulting in additional

warming of the lower atmosphere and the earth’s surface. This

“greenhouse effect” is a natural phenomenon, without which the

planet would be significantly colder and life as we know it

would not be possible. EPA, Global Warming -- Climate, at

http://yosemite.epa.gov/oar/globalwarming.nsf/content/climat

e.html.
11

2

 The rulemaking request and the papers submitted to this

court focus on the effects of CO2.

Petitioners sought to have EPA regulate, under § 202(a)(1)

of the Clean Air Act, carbon dioxide (CO2), and three other

greenhouse gases: methane (CH4), nitrous oxide (N2O), and

hydrofluorocarbons (HFCs).2 In response to EPA’s request for

public comments on the 1999 petition for rulemaking, the

agency received nearly 50,000 submissions. 68 Fed. Reg. at

52,924. Most were short expressions of support for the petition;

many were nearly identical. Id. The comment period closed in

May 2001. In the same month, the White House requested the

National Academy of Sciences to assist the Administration in its

review of climate change policy. The Academy “is a private,

nonprofit, self-perpetuating society of distinguished scholars

engaged in scientific and engineering research . . . .” NATIONAL

RESEARCH COUNCIL,CLIMATE CHANGE SCIENCE:AN ANALYSIS

OF SOME OF THE KEY QUESTIONS, preface (2001). Under its

congressional charter, issued in 1863, the Academy has a

mandate to advise the federal government on scientific and

technical matters when requested. The Academy’s principal

operating agency for providing such advice is its National

Research Council. Id.

In denying the rulemaking petition, EPA found that the

scientific comments petitioners and others submitted rested on

information already in the public domain and did not add

significantly to the body of knowledge available to the National

Research Council when it prepared the report cited above. Since

none of the comments caused EPA to question the Council’s

report, EPA decided to rely on the Council’s “objective and

independent assessment of the relevant science.” 68 Fed. Reg.

at 52,930.
12

3

 “As the NRC explained, predicting future climate change

necessarily involves a complex web of economic and physical factors

including: Our ability to predict future global anthropogenic emissions

of GHGs and aerosols; the fate of these emissions once they enter the

atmosphere (e.g., what percentage are absorbed by vegetation or are

taken up by the oceans); the impact of those emissions that remain in

the atmosphere on the radiative properties of the atmosphere; changes

in critically important climate feedbacks (e.g., changes in cloud cover

and ocean circulation); changes in temperature characteristics (e.g.,

average temperatures, shifts in daytime and evening temperatures);

changes in other climatic parameters (e.g., shifts in precipitation,

storms); and ultimately the impact of such changes on human health

and welfare (e.g., increases or decreases in agricultural productivity,

human health impacts). The NRC noted, in particular, that ‘[t]he

understanding of the relationships between weather/climate and

human health is in its infancy and therefore the health consequences

The National Research Council concluded that “a causal

linkage” between greenhouse gas emissions and global warming

“cannot be unequivocally established.” NATIONAL RESEARCH

COUNCIL, CLIMATE CHANGE SCIENCE, at 17. The earth

regularly experiences climate cycles of global cooling, such as

an ice age, followed by periods of global warming. Id. at 7.

Global temperatures have risen since the industrial revolution,

as have atmospheric levels of carbon dioxide. But an increase

in carbon dioxide levels is not always accompanied by a

corresponding rise in global temperatures. For example,

although carbon dioxide levels increased steadily during the

twentieth century, global temperatures decreased between 1946

and 1975. Id. at 16. Considering this and other data, the

National Research Council concluded that “there is considerable

uncertainty in current understanding of how the climate system

varies naturally and reacts to emissions of greenhouse gases.”

Id. at 1. This uncertainty is compounded by the possibility for

error inherent in the assumptions necessary to predict future

climate change.3

 And, as the National Research Council noted,
13

of climate change are poorly understood’ (p. 20). Substantial scientific

uncertainties limit our ability to assess each of these factors and to

separate out those changes resulting from natural variability from

those that are directly the result of increases in anthropogenic GHGs.”

68 Fed. Reg. at 52,930.

past assumptions about effects of future greenhouse gas

emissions have proven to be erroneously high. Id. at 19.

Relying on Ethyl Corp. v. EPA, 541 F.2d 1 (D.C. Cir. 1976)

(en banc), petitioners challenge EPA’s decision to forego

rulemaking “[u]ntil more is understood about the causes, extent

and significance of climate change and the potential options for

addressing it.” 68 Fed. Reg. at 52,931. In our view Ethyl

supports EPA, not petitioners. Section 202(a)(1) directs the

Administrator to regulate emissions that “in his judgment” “may

reasonably be anticipated to endanger public health or welfare.”

Section 202(a)(1) was not at issue in Ethyl; the court mentioned

an earlier version of that provision, in a footnote, only by way

of analogy. 541 F.2d at 20 n.37. But what the court had to say

about § 202(a)(1) is instructive. In requiring the EPA

Administrator to make a threshold “judgment” about whether to

regulate, § 202(a)(1) gives the Administrator considerable

discretion. Id. Congress does not require the Administrator to

exercise his discretion solely on the basis of his assessment of

scientific evidence. Id. at 20. What the Ethyl court called

“policy judgments” also may be taken into account. By this the

court meant the sort of policy judgments Congress makes when

it decides whether to enact legislation regulating a particular

area. Id. at 26.

The EPA Administrator’s analysis, although it did not

mention Ethyl, is entirely consistent with the case. In addition

to the scientific uncertainty about the causal effects of
14

greenhouse gases on the future climate of the earth, the

Administrator relied upon many “policy” considerations that, in

his judgment, warranted regulatory forbearance at this time. 68

Fed. Reg. at 52,929. New motor vehicles are but one of many

sources of greenhouse gas emissions; promulgating regulations

under § 202 would “result in an inefficient, piecemeal approach

to the climate change issue.” 68 Fed. Reg. at 52,931. The

Administrator expressed concern that unilateral regulation of

U.S. motor vehicle emissions could weaken efforts to persuade

developing countries to reduce the intensity of greenhouse gases

thrown off by their economies. Id. Ongoing research into

scientific uncertainties and the Administration’s programs to

address climate change -- including voluntary emission

reduction programs and initiatives with private entities to

develop new technology -- also played a role in the

Administrator’s decision not to regulate. 68 Fed. Reg. at

52,931-33. The Administrator pointed to efforts to promote

“fuel cell and hybrid vehicles” and ongoing efforts to develop

“hydrogen as a primary fuel for cars and trucks.” 68 Fed. Reg.

at 52,931. The Administrator also addressed the matter of

remedies. Petitioners offered two ways to reduce CO2 from new

motor vehicles: reduce gasoline consumption and improve tire

performance. As to the first, the Department of Transportation

-- the agency in charge of fuel efficiency standards -- recently

issued new standards requiring greater fuel economy, as a result

of which millions of metric tons of CO2 will never reach the

stratosphere. Id. As to tire efficiency, EPA doubted its

authority to regulate this subject as an “emission” of an air

pollutant. Id. “With respect to the other [greenhouse gases] --

CH4, N2O, and HFCs -- petitioners make no suggestion as to

how those emissions might be reduced from motor vehicles.”

Id.

It is therefore not accurate to say, as petitioners do, that the

EPA Administrator’s refusal to regulate rested entirely on
15

scientific uncertainty, or that EPA’s decision represented an

“open-ended invocation of scientific uncertainty to justify

refusing to regulate,” Brief for Petitioners at 51. A

“determination of endangerment to public health,” the court said

in Ethyl, “is necessarily a question of policy that is to be based

on an assessment of risks and that should not be bound by either

the procedural or the substantive rigor proper for questions of

fact.” Ethyl, 541 F.2d at 24. And as we have held, a reviewing

court “will uphold agency conclusions based on policy

judgments” “when an agency must resolve issues ‘on the

frontiers of scientific knowledge.’” Envtl. Def. Fund v. EPA,

598 F.2d 62, 82 (D.C. Cir. 1978).

We thus hold that the EPA Administrator properly

exercised his discretion under § 202(a)(1) in denying the petition

for rulemaking. The petitions for review in Nos. 03-1365, 03-

1366, 03-1367, and 03-1368 are dismissed, and the petitions for

review in Nos. 03-1361, 03-1362, 03-1363, and 03-1364 are

denied.

So ordered.
SENTELLE, Circuit Judge, dissenting in part and concurring

in the judgment: As the majority’s opinion observes, courts of

the United States must resolve jurisdictional questions, including

“Article III standing questions, before proceeding to the merits

of a case.” Opinion of Judge Randolph at 9 (citing Steel Co. v.

Citizens for a Better Environment, 523 U.S. 83 (1998)). As the

majority further observes, “[s]tanding exists only if the

complainant has suffered an injury in fact, fairly traceable to the

challenged action, and likely to be redressed by a favorable

decision.” Id. at 6-7 (citing Lujan v. Defenders of Wildlife, 504

U.S. 555, 560 (1992)). EPA argues “that petitioners have not

‘adequately demonstrated’ two elements of standing: that their

alleged injuries were ‘caused by EPA’s decision not to regulate

emissions of greenhouse gases from mobile sources’; and that

their injuries ‘can be redressed by a decision in their favor’ by

this court.” Id. at 7 (quoting Brief for Respondent at 16). While

I respect the majority’s thorough and accurate history of the

precedents on the standing question, after consulting the same

authorities I have come to a different conclusion. I conclude

that EPA is correct in its assertion that the petitioners have not

demonstrated the element of injury necessary to establish

standing under Article III. 

I. Injury

As the Supreme Court has stated quite directly and

succinctly:

It is an established principle that to entitle a private

individual to invoke the judicial power to determine the

validity of executive or legislative action he must show that

he has sustained or is immediately in danger of sustaining

a direct injury as the result of that action and it is not

sufficient that he has merely a general interest common to

all members of the public.
2

Ex Parte Levitt, 302 U.S. 633 (1937) (citing Tyler v. Judges, 179

U.S. 405, 406 (1900); Southern Ry. Co. v. King, 217 U.S. 524,

534 (1910); Newman v.Frizzell, 238 U.S. 537, 549, 550 (1915);

Fairchild v. Hughes, 258 U.S. 126, 129 (1922); Massachusetts

v. Mellon, 262 U.S. 447, 488) (1923)).

Thus, the courts “have consistently held that a plaintiff

raising only a generally available grievance about government

– claiming only harm to his and every citizen’s interest in proper

application of the Constitution and laws, and seeking relief that

no more directly and tangibly benefits him than it does the

public at large – does not state an Article III case or

controversy.” Lujan, 504 U.S. at 573. Or, asthe Supreme Court

has also put it, to establish Article III standing a “plaintiff must

have suffered an ‘injury in fact’– an invasion of a legally

protected interest which is (a) concrete and particularized . . .

and (b) actual or imminent, not conjectural or hypothetical.” Id.

at 560 (emphasis added; citations and internal quotation marks

omitted). Most tellingly, the Supreme Court has specifically

declared that “[b]y particularized, we mean that the injury must

affect the plaintiff in a personal and individual way.” Id. at n.1.

In the case before us, that is what the petitioners have not

established. After plowing through their reams of affidavits and

arguments, I am left with the unshaken conviction that they have

alleged and shown no harm particularized to themselves. As we

have observed in the context of determining standing even in a

procedural case, in which the standards are perhaps more

relaxed than in other cases, “in order to show that the interest

asserted is more than a mere ‘general interest . . . common to all

members of the public,’ the plaintiffs must show that the

government act . . . will cause a distinct risk to a particularized

interest of the plaintiff.” Florida Audubon Soc’y v. Bentsen, 94

F.3d 658, 664 (D.C. Cir. 1996). 
3

Petitioners’ allegations and affidavits, and petitioners’

argument and briefs, are all well made and sincere.

Nonetheless, even in the light most favorable to the petitioners,

in the end they come down to this: Emission of certain gases that

the EPA is not regulating may cause an increase in the

temperature of the earth – a phenomenon known as “global

warming.” This is harmful to humanity at large. Petitioners are

or represent segments of humanity at large. This would appear

to me to be neither more nor less than the sort of general harm

eschewed as insufficient to make out an Article III controversy

by the Supreme Court and lower courts. 

The courts under Article III stand ready to adjudicate and

redress the particularized injuries of plaintiffs, when all other

elements of jurisdiction are present. But “when the plaintiff is

not himself the object of the government action or inaction he

challenges, [although] standing is not precluded, . . . it is

ordinarily ‘substantially more difficult’ to establish.” Lujan,

504 U.S. at 562 (citations omitted). This time, in my view, it is

not only difficult, it is impossible. The generalized public good

that petitioners seek is the thing of legislatures and presidents,

not of courts. As we stated in another environmental case, to

ascertain standing courts must ask the question, did the

“underlying governmental act [or inaction] demonstrably

increase[] some specific risk of environmental harm to the

interest of the plaintiff”? Florida Audubon Soc’y, 94 F.3d at 667

(emphasis in original). Here, as in Florida Audubon, the alleged

harm is not particularized, not specific, and in my view, not

justiciable.

Therefore, I would reject and dismiss all the petitions before

us. This is not to say that petitioners’ complaints are wrong.

This is not to say they are without redress. This is to say only

that the question is not justiciable in its present form with its

present champions in the present forum. A case such as this, in
4

which plaintiffs lack particularized injury is particularly

recommended to the Executive Branch and the Congress.

Because plaintiffs’ claimed injury is common to all members of

the public, the decision whether or not to regulate is a policy call

requiring a weighing of costs against the likelihood of success,

best made by the democratic branches taking into account the

interests of the public at large. There are two other branches of

government. It is to those other branches that the petitioners

should repair.

 

II. Concurrence in the Judgment

My conclusion leaves a slight problem. No problem exists

as to the petitions for review of nonfinal action which Judge

Randolph’s opinion orders dismissed. I would dismiss those as

well, on either his ground or mine. The problem vexes only as

to petitions for review in Nos. 03-1361, 03-1362, 03-1363, and

03-1364, which Judge Randolph would deny and Judge Tatel

would grant. I would dismiss those as well, as I would hold that

we have no jurisdiction to either deny or grant them. How then

are we to reach a judgment?

The Supreme Court has suggested a way, or at least Justices

of the Supreme Court have. Most recently, in Hamdi v.

Rumsfeld, 124 S. Ct. 2633 (2004), Justice Souter, joined by

Justice Ginsburg, differed from the plurality in a fragmented

opinion adjudicating the due process rights of alleged enemy

combatants held at Guantanamo Bay by the United States

military. Justices Souter and Ginsburg would have vacated the

judgment of the Court of Appeals and remanded for proceedings

consistent with their view that the government had failed to

justify holding the petitioner. However, because that view did

not command a majority of the court, and because of “the need

to give practical effect to the conclusion of [a majority] of the

court rejecting the government’s position,” Justice Souter
5

(joined by Justice Ginsburg) joined with the plurality “in

ordering a remand on terms closest to those I would impose.”

124 S. Ct. at 2660 (Souter, J., concurring). I will take a similar

course here.

The majority today holds that we have jurisdiction to render

judgment on four of the petitions before us. Although I

disagree, I will accept the decision of the majority as dictating

the law of this case. Having so accepted the law of the case, I

will then join Judge Randolph in the issuance of a judgment

closest to that which I myself would issue. With that

explanation, I join in the decision to order denying the four

petitions from final action of the Environmental Protection

Agency. 
TATEL, Circuit Judge, dissenting in Nos. 03-1361, 03-1362,

03-1363, and 03-1364: Petitioners claim that motor vehicle

emissions of greenhouse gases contribute to global warming and

that global warming in turn is causing a host of serious

problems, likely including increased flash flood potential in the

Appalachians, degraded water quality and reduced water supply

in the Great Lakes, sea-ice melting and permafrost thawing in

Alaska, reduced summer snow-pack runoff in the Rockies,

extreme water resource fluctuations in Hawaii, and rising sea

levels combined with higher storm surges along the coasts of

Puerto Rico, the Virgin Islands, and some eastern states. See

Pet’rs Br. at 8-10 (summarizing U.S. Dep’t of State, U.S.

Climate Action Report 2002, at 110). Concerned about such

problems, petitioners asked EPA to regulate these emissions

under Clean Air Act section 202(a)(1), which provides: “The

Administrator shall by regulation prescribe . . . standards

applicable to the emission of any air pollutant from . . . new

motor vehicles . . . which in his judgment cause, or contribute to,

air pollution which may reasonably be anticipated to endanger

public health or welfare.” 42 U.S.C. § 7521(a)(1). EPA denied

the petition on two grounds—that it lacked statutory authority to

regulate such emissions and that even given such authority it

would not exercise it—and petitioners sought review in this

court.

My colleagues agree that the petitions for review should not

be granted, but they do so for quite different reasons. Judge

Sentelle thinks that petitioners lack standing and would dismiss

the petitions for that reason. Judge Randolph does not resolve

whether petitioners have standing and would deny the petitions

based on one of EPA’s two given reasons.

I have yet a different view. Unlike Judge Sentelle, I think

at least one petitioner has standing, as I explain in Part II.

Unlike Judge Randolph, I think EPA’s order cannot be sustained

on the merits. EPA’s first given reason—that it lacks statutory
2

authority to regulate emissions based on their contribution to

welfare-endangering climate change, 68 Fed. Reg. 52,922,

52,925-29 (Sept. 8, 2003)—fails, as I explain in Part III, because

the statute clearly gives EPA authority to regulate “any air

pollutant” that may endanger welfare, 42 U.S.C. § 7521(a)(1),

with “air pollutant” defined elsewhere in the statute as

“including any physical, chemical, biological, radioactive . . .

substance or matter which is emitted into or otherwise enters the

ambient air,” id. § 7602(g). EPA’s second given reason—the

one accepted by Judge Randolph—is that even if it has statutory

authority, it nonetheless “believes” that “it is inappropriate to

regulate [greenhouse gas] emissions from motor vehicles” due

to various policy reasons. As I explain in Part IV, however,

none of these policy reasons relates to the statutory

standard—“cause, or contribute to, air pollution which may

reasonably be anticipated to endanger public health or welfare,”

id. § 7521(a)(1)—and the Clean Air Act gives the Administrator

no discretion to withhold regulation for such reasons. 

In short, EPA has failed to offer a lawful explanation for its

decision. I would accordingly grant the petitions for review and

send the matter back to EPA either to make an endangerment

finding or to come up with a reasoned basis for refusing to do so

in light of the statutory standard.

I.

“Greenhouse gases are accumulating in Earth’s atmosphere

as a result of human activities, causing surface air temperatures

and subsurface ocean temperatures to rise.” So begins page one

of the National Research Council’s 2001 report, Climate Change

Science: An Analysis of Some of the Key Questions (“NRC

Report”), the scientific document EPA “rel[ied]” on in denying

the petition for rulemaking, see 68 Fed. Reg. at 52,930. 

As the NRC Report explains, greenhouse gases (GHGs) trap

heat radiated from earth, and their atmospheric concentrations
3

are increasing “as a result of human activities.” NRC Rep. at 1,

9. For example, “[h]uman activities . . . responsible for the

increase” in atmospheric concentrations of carbon dioxide

(CO2)—the chief GHG—include “[t]he primary source, fossil

fuel burning,” as well as “[t]ropical deforestation.” Id. at 2; see

also id. at 10, 12. The resulting increases are striking. In the

400,000 years prior to the Industrial Revolution, atmospheric

CO2 concentrations “typically ranged between 190” parts per

million by volume (ppmv) “during the ice ages to near 280

ppmv during the warmer ‘interglacial’ periods.” Id. at 11. By

1958, atmospheric concentrations were 315 ppmv (12.5% above

the pre-Industrial-Revolution high of 280 ppmv), and by 2000

they had risen to 370 ppmv (17% above the 1958 level). Id. at

10. Similarly, prior to the Industrial Revolution, atmospheric

concentrations of methane (CH4), another GHG, ranged from .3

ppmv to .7 ppmv; now, “current values are around 1.77 ppmv.”

Id. at 11. Atmospheric concentrations of other GHGs like

nitrous oxide (N2O) have also risen. Id. at 2. Notably, GHGs

not only disperse throughout the lower atmosphere, but also

linger there at length: “Reductions in the atmospheric

concentrations of these gases following possible lowered

emissions rates in the future will stretch out over decades for

methane, and centuries and longer for carbon dioxide and

nitrous oxide.” Id. at 10. 

Increased GHG atmospheric concentrations are causing

“climate forcings”—“imposed perturbation[s] of Earth’s energy

balance” measured in terms of units of watts per square meter

(W/m2

). Id. at 6. Drawing from another report—an

Intergovernmental Panel on Climate Change (IPCC) report with

which the NRC “generally agrees,” id. at 1—the NRC Report

quantifies these climate forcings. CO2, “probably the most

important climate forcing agent today,” has “caus[ed] an

increased forcing of about 1.4 W/m2

” between 1750 and 2000.

Id. at 12, 13. More lies ahead: 
4

CO2 climate forcing is likely to become more dominant in

the future as fossil fuel use continues. If fossil fuels

continue to be used at the current rate, the added CO2

forcing in 50 years will be about 1 W/m2. If fossil fuel use

increases by 1-1.5% per year for 50 years, the added CO2

forcing instead will be about 2 W/m2.

Id. at 12-13. Thus, by 2050, the total CO2 forcing since 1750

could be from 2.4-3.4 W/m2

. The other GHGs “together cause

a climate forcing approximately equal to that of CO2,” or more

if one includes certain indirect effects of increased CH4

emissions. Id. at 13. While atmospheric GHG increases are not

the only causes of climate forcings—for example, changes in

solar irradiance and in concentrations of tropospheric ozone also

appear to have caused climate forcings, and atmospheric

concentration changes in aerosols like sulphates appear to have

caused negative (cooling) climate forcings—all other forcings

are less certain and appear less substantial than those caused by

GHGs. See id.

The extent to which these forcings affect average global

temperatures depends on the climate’s sensitivity, a condition

that is not precisely known. Id. at 7. “Well-documented climate

changes . . . imply that the climate sensitivity is near . . . 3oC”

(5.4oF) for a 4 W/m2

 forcing—a number a bit above the total

CO2 forcing predicted by 2050—“but with a range from 1.5oC

to 4.5oC (2.7 to 8.1oF).” Id.

Turning to the practical effects of GHG climate forcings,

the NRC Report observes that a “diverse array of evidence

points to a warming of global surface temperatures.” Id. at 16.

Though the “rate of warming has not been uniform,”

measurements “indicate that global mean surface air temperature

warmed by about .4-.8oC (.7-1.5oF) during the 20th century.” Id.

The report notes that “[t]he Northern Hemisphere as a whole

experienced a slight cooling from 1946-75,”—a statement Judge

Randolph erroneously reads for the proposition that “global
5

temperatures decreased between 1946 and 1975,” op. of

Randolph, J., at 12 (emphasis added)—possibly due to the

widespread burning of high sulfur coal and resultant sulfate

emissions or to changes in ocean circulation in the Atlantic.

NRC Rep. at 16. The report also observes that, as the IPCC

report points out, the “warming of the Northern Hemisphere

during the 20th century is likely to have been the largest of any

century in the past thousand years.” Id.

In evaluating the relationship between GHG atmospheric

increases and twentieth-century temperature increases, the NRC

Report states that due to the

large and still uncertain level of natural variability inherent

in the climate record and the uncertainties in the time

histories of various forcing agents (and particularly

aerosols), a causal linkage between the buildup of

greenhouse gases in the atmosphere and the observed

climate changes during the 20th century cannot be

unequivocally established. 

Id. at 17. Although Judge Randolph seizes on this

uncertainty—and portrays it as applying to global warming

generally rather than to twentieth-century warming, see op. of

Randolph, J., at 11—read in context, it appears little more than

an application of the principle that, as the NRC Report later puts

it, “[c]onfidence limits and probabilistic information, with their

basis, should always be considered as an integral part of the

information that climate scientists provide to policy and decision

makers,” NRC Rep. at 22. Indeed, the NRC Report goes on to

state that the “fact that the magnitude of the observed warming

is large compared to natural variability as simulated in climate

models is suggestive of such a linkage” between GHG

atmospheric concentration increases and twentieth-century

temperature increases, though not “proof” of it. Id. at 17.

The NRC Report further suggests that uncertainties about
6

future warming relate chiefly to its scope.

Climate change simulations for the period of 1990 to 2100

based on IPCC emissions scenarios yield a globallyaveraged surface temperature increase by the end of the

century of 1.4 to 5.8oC (2.5 to 10.4oF) relative to 1990. The

wide range of uncertainty in these estimates reflects both

the different assumptions about future concentrations of

greenhouse gases and aerosols in the various scenarios

considered by the IPCC and the differing climate

sensitivities of the various climate models used in the

simulations. The range of climate sensitivities implied by

these predictions is generally consistent with previously

reported values.

Id. at 3. These numbers, of course, are averages: the “predicted

warming is higher over higher latitudes than low latitudes,

especially during winter and spring, and larger over land than

over sea.” Id.

With this warming will come secondary effects. Predicted

impacts in the United States include increased likelihood of

drought, greater heat stress in urban areas, rising sea levels, and

disruption to many U.S. ecosystems. Id. at 19-20. The

likelihood and scope of these impacts vary depending on the

magnitude of future temperature increases. See id.; see also id.

at 4. Because the “predicted temperature increase is sensitive to

assumptions concerning future concentrations of greenhouse

gases and aerosols,” which in turn depend on future emissions,

“national policy decisions made now and in the longer-term

future will influence the extent of any damage suffered by

vulnerable human populations and ecosystems later in this

century.” Id. at 1. 
7

II.

EPA claims petitioners lack standing to bring this case. To

reach the merits, however, we need determine only that one

petitioner has standing. See, e.g., Nuclear Energy Inst., Inc. v.

EPA, 373 F.3d 1251, 1266 (D.C. Cir. 2004). In my view,

declarations submitted by petitioners clearly establish that the

Commonwealth of Massachusetts has satisfied each element of

Article III standing—injury, causation, and redressability, see,

e.g., Lujan v. Defenders of Wildlife, 504 U.S. 555, 560-61

(1992).

Among other things, Massachusetts claims injury—the

“substantial probability that local conditions will be adversely

affected,” Sierra Club v. EPA, 292 F.3d 895, 898 (D.C. Cir.

2002) (internal quotation marks omitted)—resulting from rising

sea levels. The declaration of Paul Kirshen, a professor at Tufts

University’s Civil and Environmental Engineering Department,

details how projected rises in sea levels in the metropolitan

Boston area would lead both to permanent loss of coastal land

and to “more frequent and severe storm surge flooding events

along the coast.” Kirshen Decl. ¶¶ 7-8; see also Jacqz Decl. ¶¶

8-11. “[I]f sea level rises .3 meters (11.8 inches)—which is near

the lower end of the likely range—that would mean the future

10-year flood surge elevation would be at the level of the current

100-year flood elevation and the future 100-year flood surge

elevation would be at that of the current 500-year flood

elevation.” Kirshen Decl. ¶ 10. As other declarations make

clear, such changes would lead to serious loss of and damage to

Massachusetts’s coastal property. See Hoogeboom Decl. ¶¶ 6-7;

Jacqz Decl. ¶ 11.

Given these declarations, I disagree that no petitioner

suffers “harm particularized to” itself. See op. of Sentelle, J., at

2. The Commonwealth of Massachusetts claims an

injury—namely, loss of land within its sovereign

boundaries—that “affects [it] in a personal and individual way,”
8

Lujan, 504 U.S. at 560 n.1. This loss (along with increased

flood damage to the Massachusetts coast) undeniably harms the

Commonwealth in a way that it harms no other state. Other

states may face their own particular problems stemming from

the same global warming—Maine may suffer from loss of

Maine coastal land and New Mexico may suffer from reduced

water supply—but these problems are different from the injuries

Massachusetts faces. Massachusetts’s harm is thus a far cry

from the kind of generalized harm that the Supreme Court has

found inadequate to support Article III standing, i.e., “harm to

[its] and every citizen’s interest in proper application of the

Constitution and laws,” or put another way “relief that no more

directly and tangibly benefits [it] than it does the public at

large,” id. at 573-74.

As to causation, the declaration of Michael MacCracken,

the senior scientist on global change at the Office of the U.S.

Global Change Research Program from 1993-2002, states that

global warming is causing sea level increases like those in

Massachusetts. “[T]he warming of the oceans and the increased

melting of many mountain glaciers around the world . . . were

the major contributions to the rise in global sea level by 10-20

cm (4 to 8 inches) observed over the past century” and the

“environmental impacts of projected global warming will

include . . . an increase in sea level at an average rate of about .5

to 3.5 inches per decade, reaching 4-35 inches by the end of the

century (with the most likely value being, in my expert opinion,

near or above the middle of this range).” MacCracken Decl. ¶

5(c)-(d); see also id. ¶ 23. MacCracken further states that global

warming is chiefly triggered by human-caused GHG emissions,

see id. ¶¶ 5(a)-(b), 12-19, with “the U.S. transportation sector

(mainly automobiles) . . . responsible for about 7% of global

fossil fuel emissions,” id. ¶ 31.

Finally, as to redressability, MacCracken emphasizes that

“[a]chievable reductions in emissions of CO2 and other [GHGs]
9

from U.S. motor vehicles would . . . delay and moderate many

of the adverse impacts of global warming.” Id. ¶5(e).

Elaborating, he states that “[g]iven the large emissions of CO2

and other [GHGs] from motor vehicles in the United States and

the lead time needed to economically introduce changes into the

motor vehicle fleet, emission reductions must be initiated in the

near future in order to significantly reduce and delay the impacts

of global warming.” Id. ¶ 31. Because the extent of damage to

the Massachusetts coastline depends on the magnitude of the

rise in sea level, a reduction in this projected adverse

consequence of global warming would partially redress

Massachusetts’s injury. See Tozzi v. U.S. Dep’t of Health &

Human Servs., 271 F.3d 301, 310 (D.C. Cir. 2001) (holding that

a petitioner need only demonstrate it would receive “at least

some” relief to establish redressability). Nowhere disputing this

proposition, EPA instead claims that MacCracken’s conclusion

depends upon the assumption that other countries will follow the

U.S. lead and regulate motor vehicle GHG emissions. Even

were this reading of the declaration correct—a dubious premise

given MacCracken’s unqualified language focusing on U.S.

emissions reduction—the uncontested declaration of Michael

Walsh, a consultant on motor vehicle pollution technology and

at one point director of EPA’s motor vehicle pollution control

efforts, provides a basis for concluding that other countries

would come to mandate technology developed in response to

U.S. regulation. Describing how in the past other countries have

come to require such technology, Walsh concludes that “[o]n the

basis of my experience with the control of other pollutants . . .

I have no doubt that establishing emissions standards for

pollutants that contribute to global warming would lead to

investment in developing improved technologies to reduce those

emissions from motor vehicles, and that successful technologies

would gradually be mandated by other countries around the

world.” Walsh Decl. ¶¶ 7-8, 10. 

Judge Randolph, accepting that the declarations “do
10

‘support each element’ of standing,” nonetheless questions

whether this is enough. See op. of Randolph, J., at 8 (quoting

Sierra Club, 292 F.3d at 899). Specifically, he believes we

confront a question left open in our Sierra Club decision. In that

case, we held that “[t]he petitioner’s burden of production in the

court of appeals is . . . the same as that of a plaintiff moving for

summary judgment in the district court: it must support each

element of its claim to standing ‘by affidavit or other

evidence.’” 292 F.3d at 899 (quoting Lujan, 504 U.S. at 561).

But we never explicitly addressed what happens if the agency

submits evidence that contradicts that of petitioners. Do we

resolve factual disputes in petitioners’ favor, return the case to

the agency for fact-finding, send the matter to a special master,

or pursue some other course of action? 

The issue is fascinating, but we need not confront it. Given

that the burdens of production here are comparable to those at

summary judgment, see 292 F.3d at 899, if EPA wants to

challenge the facts petitioners have set forth in their affidavits,

it has an obligation to respond to the petitioners by “citing any

record evidence relevant to . . . standing and, if necessary,

appending to its filing additional affidavits or other evidence,”

see id. at 900-01. EPA makes no such challenge. 

Indeed, if anything, the order under review appears to

support petitioners’ standing. While, drawing on the NRC

Report, EPA observes that “there continue to be important

uncertainties in our understanding of the factors that may affect

future climate change,” 68 Fed. Reg. at 52,930, EPA never

denies the “substantial probability,” see Sierra Club, 292 F.3d

at 898, that injurious global warming is occurring. Quite to the

contrary, EPA “agree[s] with the President that ‘we must

address the issue of global climate change.’” 68 Fed. Reg. at

52,929 (quoting presidential statement of Feb. 14, 2002). As to

causation and redressability, the petition denial emphasizes that

“EPA is also working to encourage voluntary GHG emission
11

reductions from the transportation sector” and that “the

Administration’s global climate change policy includes

promoting the development of fuel-efficient motor vehicles and

trucks, researching options for producing cleaner fuels, and

implementing programs to improve energy efficiency.” Id. at

52,932; see also NRC Rep. at 1 (noting that “national policy

decisions made now . . . will influence the extent of any

damage” caused by global warming). EPA would presumably

not bother with such efforts if it thought emissions reductions

would have no discernable impact on future global warming.

Because EPA nowhere challenges petitioners’ declarations,

I see no reason to consider what we would do if it had done so.

Thus, unlike Judge Randolph, I think it unnecessary to address

whether we can carve out exceptions to the Supreme Court’s

seemingly unqualified holding that “a merits question cannot be

given priority over an Article III question,” Steel Co. v. Citizens

for a Better Env’t, 523 U.S. 83, 97 n.2 (1998). The

Commonwealth of Massachusetts has adequately demonstrated

its standing, and our jurisdiction is plain.

III.

As to the merits, the threshold question is this: does the

Clean Air Act authorize EPA to regulate emissions based on

their effects on global climate? Taking a constricted view, EPA

insists it has no authority to regulate GHG emissions even if

they contribute to substantial and harmful global warming. By

contrast, petitioners claim that Congress has plainly given EPA

the authority it says it lacks.

“If a court, employing traditional tools of statutory

construction, ascertains that Congress had an intention on the

precise question at issue, that intention is the law and must be

given effect.” Chevron U.S.A., Inc. v. Natural Res. Def.

Council, Inc., 467 U.S. 837, 843 n.9 (1984). The inquiry

“begin[s], as always, with the plain language of the statute in
12

question.” Consumer Elecs. Ass’n v. FCC, 347 F.3d 291, 297

(D.C. Cir. 2003) (quoting Citizens Coal Council v. Norton, 330

F.3d 478, 482 (D.C. Cir. 2003)). CAA section 202(a)(1), added

by Congress in 1965 and amended in 1970 and 1977, provides,

The Administrator shall by regulation prescribe . . .

standards applicable to the emission of any air pollutant

from any class or classes of new motor vehicles or new

motor vehicle engines which in his judgment cause, or

contribute to, air pollution which may reasonably be

anticipated to endanger public health or welfare.

42 U.S.C. § 7521(a)(1). This language plainly authorizes

regulation of (1) any air pollutants emitted from motor vehicles

that (2) in the Administrator’s judgment cause, or contribute to,

air pollution which may reasonably be anticipated to endanger

public health or welfare. EPA’s claimed lack of authority

relates to the first of these two elements. According to EPA,

GHGs like CO2, CH4, N2O, and hydrofluorocarbons (HFCs) “are

not air pollutants.” 68 Fed. Reg. at 52,928.

Congress, however, left EPA little discretion in determining

what are “air pollutants.” Added in 1970 and amended in 1977,

CAA section 302(g) defines the term as follows: 

The term ‘air pollutant’ means any air pollution agent or

combination of such agents, including any physical,

chemical, biological, radioactive . . . substance or matter

which is emitted into or otherwise enters the ambient air.

42 U.S.C. § 7602(g). This exceedingly broad language plainly

covers GHGs emitted from motor vehicles: they are “physical

[and] chemical . . . substance[s] or matter . . . emitted into . . .

the ambient air.” Indeed, in one CAA provision, added in 1990,

Congress explicitly included CO2 in a partial list of “air

pollutants.” Section 103(g) instructs the Administrator to

research “nonregulatory strategies and technologies for

preventing or reducing multiple air pollutants, including sulfur
13

oxides, nitrogen oxides, heavy metals, PM-10 (particulate

matter), carbon monoxide, and carbon dioxide.” Id. § 7403(g)

(emphasis added). Faced with such language, a court—as well

as an agency—would normally end the analysis here and

conclude that GHGs are “air pollutants,” since “[w]e ‘must

presume that a legislature says in a statute what it means and

means in a statute what it says . . . . When the words of a statute

are unambiguous . . . this first canon is also the last: judicial

inquiry is complete.’” Teva Pharm. Indus. Ltd. v. Crawford,

410 F.3d 51, 53 (D.C. Cir. 2005) (quoting Conn. Nat’l Bank v.

Germain, 503 U.S. 249, 253-54 (1992)) (omissions in original).

Unswayed by what it calls “narrow semantic analyses,”

Resp’t Br. at 55—but what courts typically call Chevron step

one—EPA claims that a “more holistic analysis . . . [of] the text,

structure, and history of the CAA as a whole, as well as the

context provided by other legislation that is specific to climate

change,” justifies its conclusion that it cannot regulate GHGs

like CO2 for their effects on climate change, id. at 25-26. To

disregard the Act’s plain text in this way, EPA needs an

“extraordinarily convincing justification.” Appalachian Power

Co. v. EPA, 249 F.3d 1032, 1041 (D.C. Cir. 2001). “For the

EPA to avoid a literal interpretation at Chevron step one, it must

show either that, as a matter of historical fact, Congress did not

mean what it appears to have said, or that, as a matter of logic

and statutory structure, it almost surely could not have meant it.”

Engine Mfrs. Ass’n v. EPA, 88 F.3d 1075, 1089 (D.C. Cir.

1996). 

EPA offers four reasons for abandoning the Act’s text.

First, it suggests that since the 1965, 1970, and 1977 Congresses

were not specifically concerned with global warming, the Act

cannot apply to GHGs. Second, it claims that for both practical

and policy reasons, global pollution should be tackled through

specific statutory provisions rather than general ones. Third,

relying on FDA v. Brown & Williamson Tobacco Corp., 529
14

U.S. 120 (2000), it argues that Congress’s passage of legislation

calling for study of climate change, along with Congress’s

failure to pass any provisions tailored solely to regulating

GHGs, demonstrates that the CAA cannot apply to GHGs.

Finally, EPA suggests that Congress couldn’t have intended the

definition of “air pollutant” to cover CO2, since EPA regulation

of CO2 emissions from automobiles would overlap with

Department of Transportation (DOT) authority over fuel

economy standards under a different act. None of these reasons

provides a convincing justification—let alone an

“extraordinarily convincing” one—for EPA’s counter-textual

position.

EPA first suggests that because the 1965, 1970, and 1977

Congresses showed little concern about the specific problem of

global warming, reading the CAA’s language to cover such

problems would be like finding “an elephant in a mousehole.”

Tr. of Oral Arg. at 32; see also Resp’t Br. at 23 (quoting

Whitman v. Am. Trucking Ass’ns, 521 U.S. 457, 468 (2002)).

EPA is correct that those Congresses spilled little ink on the

issue of global warming: while the legislative history contains

a few stray references to human-forced climate change, see, e.g.,

111 Cong. Rec. 25,061 (Sept. 24, 1965) (statement of Rep.

Helstoski); 116 Cong. Rec. 32,914 (Sept. 21, 1970) (report

introduced in the record by Sen. Boggs), in those years the

scientific understanding of the issue was nascent at best, see,

e.g., Environmental Quality: The First Annual Report of the

Council on Environmental Quality 93 (1970) (noting that “[m]an

may be changing his weather” but expressing uncertainty as to

whether global warming or cooling was occurring). But EPA

errs in suggesting that because Congress may not have precisely

foreseen global warming, the Act provides no authorization for

GHG regulation. Hardly a mousehole, the definition of “air

pollutants”—“including any physical, chemical, biological,

radioactive . . . substance or matter which is emitted into or

otherwise enters the ambient air”—enables the Act to apply to
15

new air pollution problems as well as existing ones. “[T]he fact

that a statute can be applied in situations not expressly

anticipated by Congress,” the Supreme Court has explained,

“does not demonstrate ambiguity. It demonstrates breadth.”

PGA Tour, Inc. v. Martin, 532 U.S. 661, 689 (2001) (quoting

Pa. Dep’t of Corrections v. Yeskey, 524 U.S. 206, 212 (1998)).

Indeed, Congress expressly instructed EPA to be on the lookout

for climate-related problems in evaluating risks to “welfare.”

Section 302(h), added in 1970, explains that “[a]ll language

referring to effects on welfare includes, but is not limited to,

effects on soils, water, crops, vegetation, manmade materials,

animals, wildlife, weather, visibility, and climate.” 42 U.S.C. §

7602(h) (emphasis added).

EPA’s second reason for its interpretation—that for

practical and policy reasons global warming should be dealt

with through specifically tailored statutes—likewise fails to

trump Congress’s plain language. It may well be that a statute

aimed solely at global warming would deal with the problem

more effectively than one aimed generally at air pollution. But

an agency may not “avoid the Congressional intent clearly

expressed in the [statutory] text simply by asserting that its

preferred approach would be better policy.” Engine Mfrs. Ass’n,

88 F.3d at 1089. Perhaps recognizing this point, EPA attempts

to link its policy arguments to the statute by claiming that

because the 1977 and 1990 Congresses enacted provisions

specific to another global pollution problem—depletion of

stratospheric ozone—we must infer that the Act’s general

provisions do not cover such global problems. Once again, EPA

makes much of very little. While the 1977 Congress did add

provisions aimed specifically at ozone depletion, it also made

clear that “[n]othing in this [ozone-specific] part shall be

construed to alter or affect the authority of the Administrator

under . . . any other provision of this Act.” Pub. L. No. 95-95,

§ 158, 91 Stat. 685, 730 (1977); see also H.R. Rep. No. 95-294,

at 102 (1977) (expressing the House Committee’s view that
16

EPA could already regulate emissions to protect stratospheric

ozone under an existing general provision of the CAA).

Similarly, I see nothing in the 1990 Congress’s enactment of

other provisions specific to stratospheric ozone protection, see

42 U.S.C. §§ 7671 to 7671q, indicating it thought EPA lacked

authority under general provisions like section 202 to regulate

emissions contributing to global pollution. This is particularly

true since that Congress also enacted provisions specific to

certain regional pollutants, see, e.g., id. §§ 7651 to 7651o (acid

rain control), which, pursuant to general CAA provisions, EPA

already had authority to regulate. 

EPA also attempts an unworkability argument. Its

argument goes like this: another part of the CAA provides that

the Administrator shall maintain a list of air pollutants that,

among other things, “in [the Administrator’s] judgment, cause

or contribute to air pollution which may reasonably be

anticipated to endanger public health or welfare.” Id. §

7408(a)(1)(A). Once pollutants go on this list, the Administrator

must set national ambient air quality standards (NAAQS) for

them, i.e., ambient air concentration levels that, in the

Administrator’s judgment, “are requisite to protect the public

health” and in some areas are “requisite to protect the public

welfare.” Id. § 7409(b); see also id. §§ 7407, 7410(a)(1). States

must submit plans explaining how they will achieve these

NAAQS. Id. § 7410. According to EPA, these provisions

would be unworkable if applied to CO2: because CO2 disperses

relatively evenly throughout the lower atmosphere, states would

have only minimal control over their atmospheric CO2

concentrations and thus over whether they meet the CO2

NAAQS. EPA then concludes that because CO2 regulation

would be unworkable in the NAAQS context, no general CAA

provisions, including section 202(a)(1), authorize it to regulate

any GHGs. 

This unwieldy argument fails. Even assuming that states’
17

limited ability to meet CO2 NAAQS renders these provisions

unworkable as to CO2, but see id. § 7509a(a) (providing a safe

harbor for states that fail to meet NAAQS due to emissions

emanating from outside the country), the absurd-results canon

would justify at most an exception limited to the particular

unworkable provision, i.e., the NAAQS provision. See Mova

Pharm. Corp. v. Shalala, 140 F.3d 1060, 1068 (D.C. Cir. 1998).

As EPA acknowledges, regulating CO2 emissions from

automobiles is perfectly feasible. See 68 Fed. Reg. at 52,929

(noting that “improving fuel economy” is a “practical way of

reducing tailpipe CO2 emissions” and that other technologies for

reducing emissions may develop in the future).

In support of its third justification for abandoning the plain

text of sections 202(a)(1) and 302(g), EPA relies on later

congressional action (and inaction). Specifically, EPA points

out (1) that all direct references to CO2 or global warming in the

1990 CAA amendments appear in nonregulatory provisions; (2)

that other congressional acts such as the 1978 National Climate

Program Act, the 1987 Global Climate Protection Act, the 1990

Global Change Research Act, and the 1992 Energy Policy Act,

as well as several appropriations riders, touch specifically on the

issue of global warming, typically by instructing agencies to

study the issue; and (3) that Congress has considered and

rejected many bills specifically tailored to GHG emissions

regulation since at least 1990. One might well wonder what all

this has to do with whether GHGs are “air pollutants” within the

meaning of CAA section 302(g). But relying almost exclusively

on Brown & Williamson, 529 U.S. 120, EPA claims that

together these facts indicate that the CAA’s general provisions

do not cover GHGs. EPA also asserts that, as in Brown &

Williamson, the “extraordinary” political and economic

significance of the regulation requested casts doubt on the

agency’s authority to undertake it. See Resp’t Br. at 21-22.

In Brown & Williamson, the Court considered whether the
18

FDA had authority to regulate tobacco products. Although the

Food, Drug, and Cosmetic Act’s broad language suggested that

it did, the Court, acknowledging that “a specific policy

embodied in a later federal statute should control our

construction of the [earlier] statute, even though it ha[s] not been

expressly amended,” 529 U.S. at 143 (quoting United States v.

Estate of Romani, 523 U.S. 517, 530-31 (1998)) (alterations in

original), concluded that the FDA lacked such authority. In

reaching this conclusion, the Court relied on a direct,

irreconcilable conflict between FDA jurisdiction over tobacco

under the FDCA and later statutes expressly regulating tobacco.

If the FDA had jurisdiction over tobacco products, it would have

had to ban them entirely due to their health risks, yet the

subsequent acts “reveal[ed Congress’s] intent that tobacco

products remain on the market.” 529 U.S. at 139. Moreover, as

the Court emphasized—at least eighteen times by my

count—the FDA had repeatedly claimed to have “no authority

under the FDCA to regulate tobacco products,” id. at 157, and

“Congress’s tobacco-specific statutes ha[d] effectively ratified

the FDA’s long-held position,” id. at 144. See generally id. at

125-26, 130-31, 144-46, 151-57. 

EPA’s reliance on Brown & Williamson is misplaced. To

begin with, I am unconvinced by EPA’s contention that its

jurisdiction over GHG emissions would be as significant as

FDA jurisdiction over tobacco. Acting under the CAA, EPA

already extensively regulates the energy and transportation

industries, whereas the FDA had no prior authority over the

tobacco industry. Moreover, EPA jurisdiction would lead only

to regulation of GHGs—with, in the case of section 202,

regulation taking effect only after “such period as the

Administrator finds necessary” for development of technology,

“giving appropriate consideration to the cost of compliance,” 42

U.S.C. § 7521(a)(2). By contrast, FDA jurisdiction over tobacco

would have triggered a total product ban. But even assuming

the implications are equally significant, this is not an
19

“extraordinary” case where “common sense,” see Brown &

Williamson, 529 U.S. at 133, 159, calls into question whether

Congress has delegated EPA authority to regulate GHGs.

Congress gave EPA broad authority to regulate all harmful

pollutants, as section 202(a)(1)’s text makes clear. Congress did

so intentionally, deeming it “not appropriate to exempt certain

pollutants” from the Act’s “comprehensive protections.” See

H.R. Rep. No. 95-294, at 42-43. And, as I explain below, no

subsequent statutory indicia comparable to those relied on by the

Court in Brown & Williamson justify a different conclusion.

Perhaps most significantly, no conflict exists between

EPA’s section 202(a)(1) authority to regulate GHGs and

subsequent global warming legislation. Whereas an FDA ban

on tobacco would have directly conflicted with congressional

intent that tobacco remain on the market, EPA regulation of

GHGs would be fully compatible with statutes proposing

additional research and other nonregulatory approaches to

climate change. Take the three 1990 CAA additions referencing

carbon dioxide or global warming. Section 103(g) calls for

“nonregulatory strategies and technologies” for reducing

pollutants like sulpher oxides, carbon monoxide, and carbon

dioxide. 42 U.S.C. § 7403(g). While the section also provides

that “[n]othing in this subsection shall be construed to authorize

the imposition on any person of air pollution control

requirements,” id. (emphasis added), it nowhere suggests that

EPA lacks authority to regulate carbon dioxide—or, for that

matter, sulpher oxides, carbon monoxide, and other

pollutants—under different parts of the Act. Section 602(e) is

similar. One sentence requires the Administrator to “publish the

global warming potential” of certain listed substances, and the

next sentence notes that “[t]he preceding sentence shall not be

construed to be the basis of any additional regulation under this

chapter.” Id. § 7671a(e). Once again, nothing in this provision

bars regulation under other parts of the Act. The third

provision—an uncodified section—merely requires sources
20

subject to the Act’s Title V to “monitor carbon dioxide

emissions,” and says nothing about regulation one way or the

other. Pub. L. No. 101-549, § 821, 104 Stat. 2399, 2699 (1990).

Other climate-related acts similarly demonstrating congressional

intent that global climate issues receive study and attention are

likewise perfectly compatible with GHG regulation. See

generally National Climate Program Act of 1978, Pub. L. No.

95-367, 92 Stat. 601; Global Climate Protection Act of 1987,

Pub. L. No. 100-204, §§ 1101-1106, 101 Stat. 1331, 1407-09;

Global Change Research Act of 1990, Pub. L. No. 101-606, 104

Stat. 3096; Energy Policy Act of 1992, Pub. L. No. 102-486, 106

Stat. 2776.

Furthermore, and unlike subsequent tobacco legislation that

“effectively ratified the FDA’s previous position,” Brown &

Williamson, 529 U.S. at 156, this subsequent global-warmingrelated legislation passed without any assurance from EPA that

the agency lacked authority to regulate GHGs. Quite to the

contrary, at the time of the two appropriations riders relied on by

EPA, see, e.g., Pub. L. No. 105-276, 112 Stat. 2461, 2496

(1998) (barring use of funds for implementation of the Kyoto

Protocol), EPA was taking the position that it possessed general

authority to regulate GHG emissions under section 202(a)(1).

See Memorandum, J. Cannon to C. Browner (April 10, 1998).

Finally, the fact that later Congresses failed to pass bills

specifically tailored to regulating global warming hardly

provides a basis for inferring that earlier Congresses meant to

exclude climate-endangering pollutants from the coverage of the

CAA’s general provisions. Not only is “subsequent legislative

history . . . a ‘hazardous basis for inferring the intent of an

earlier’ Congress,” but it “is a particularly dangerous ground . .

. when it concerns, as it does here . . . proposal[s] that do[] not

become law.” Pension Benefit Guar. Corp. v. LTV Corp., 496

U.S. 633, 650 (1990) (citation omitted). Indeed, in interpreting

the scope of the FDA’s authority, the Brown & Williamson

Court itself expressly declined to rely on failed legislation. 529
21

U.S. at 155.

EPA has one last argument, applicable to CO2 emissions

alone, for claiming it lacks the authority the language of sections

202(a)(1) and 302(g) expressly bestow upon it. According to

EPA, the only practical way to regulate CO2 emissions from

motor vehicles is to require increased fuel economy, since CO2

is a byproduct of fuel combustion and “[n]o technology

currently exists or is under development that can capture and

destroy or reduce” CO2 “emissions from motor vehicle

tailpipes.” 68 Fed. Reg. at 52,929. Such regulation, EPA

reasons, would overlap substantially with DOT’s authority under

the 1975 Energy Policy and Conservation Act (EPCA) to set

average fuel economy standards for certain classes of motor

vehicles. See Pub. L. No. 94-163, § 502, 89 Stat. 871, 902-07

(1975). Though recognizing that no direct conflict would occur

since both agencies would set minimum standards, EPA

concludes that “any EPA effort to set CO2 tailpipe emissions

under the CAA would either abrogate EPCA’s regime (if the

standards were effectively more stringent than the applicable

[DOT] standard) or be meaningless (if they were effectively less

stringent).” 68 Fed. Reg. at 52,929. 

EPA may well be correct that setting standards for fuel

economy (rather than for capturing tailpipe emissions)

represents its only currently practical option for regulating CO2

emissions. But cf. 42 U.S.C. § 7521(a)(2) (requiring section

202(a)(1) regulation to take effect only “after such period as the

Administrator finds necessary to permit the development and

application of the requisite technology”). But given that the two

regulatory regimes—one targeted at fuel conservation and the

other at pollution prevention—are overlapping, not

incompatible, there is no reason to assume that Congress

exempted CO2 from the meaning of “air pollutant” within the

CAA, particularly since section 103(g) explicitly calls CO2 an

“air pollutant.” Where two “statutes are ‘capable of co-
22

existence,’ it becomes the duty of this court ‘to regard each as

effective’—at least absent clear congressional intent to the

contrary.” FTC v. Ken Roberts Co., 276 F.3d 583, 593 (D.C.

Cir. 2001) (quoting Morton v. Mancari, 417 U.S. 535, 551

(1974)). Moreover, Congress acknowledged, and indeed

accepted, the possibility of regulatory overlap. Not only does

the current EPCA recognize the relevance of “the effect of other

motor vehicle standards of the Government on fuel economy,”

49 U.S.C. § 32902(f); see also EPCA, Pub. L. No. 94-163, §

502(e), 89 Stat. at 905, but in passing the 1977 CAA

amendments Congress emphasized that EPA regulation under

the CAA should go forward even where it overlaps with

responsibilities given to other agencies under other acts, see

H.R. Rep. No. 95-294, at 42-43 (explaining that Congress was

amending section 302(g) to broaden the meaning of “air

pollutants” and make clear that EPA has authority even over

pollutants already regulated by another agency). As the 1977

House Report explained, “the Clean Air Act is the

comprehensive vehicle for protection of the Nation’s health

from air pollution. In the committee’s view, it is not appropriate

to exempt certain pollutants or certain sources from the

comprehensive protections afforded by the Clean Air Act.” Id.

In sum, GHGs plainly fall within the meaning of “air

pollutant” in section 302(g) and therefore in section 202(a)(1).

If “in [the Administrator’s] judgment” they “cause, or contribute

to, air pollution which may reasonably be anticipated to

endanger public health or welfare,” 42 U.S.C. § 7521(a)(1), then

EPA has authority—indeed, the obligation—to regulate their

emissions from motor vehicles. 

IV.

EPA’s second reason for refusing to act—what EPA’s

counsel termed “the fallback argument,” Tr. of Oral Arg. at

41—is that even if GHGs are air pollutants, the agency gave
23

appropriate reasons and acted within its discretion in denying

the petition for rulemaking. EPA stresses that our “arbitrary and

capricious” standard of review is particularly deferential in

reviewing an agency refusal to institute rulemaking. See Resp’t

Br. at 11-12; cf. Motor Vehicle Mfrs. Ass’n v. EPA, 768 F.2d

385, 389 n.6 (D.C. Cir. 1985) (observing that the CAA judicial

review provisions are identical to those in the APA). This is

certainly true, but this court must nonetheless “consider whether

the agency’s decisionmaking was reasoned,” and we will not

permit the agency to make “plain errors of law.” See Am. Horse

Protection Ass’n, Inc. v. Lyng, 812 F.2d 1, 5 (D.C. Cir. 1987)

(internal quotation marks omitted). Indeed, “the agency has the

heaviest of obligations to explain and expose every step of its

reasoning,” so that we can “exercis[e] our responsibility to

determine whether [its] decision is ‘arbitrary, capricious, an

abuse of discretion, or otherwise not in accordance with law.’”

See Am. Lung Ass’n v. EPA, 134 F.3d 388, 392-93 (D.C. Cir.

1998) (quoting 42 U.S.C. § 7607(d)(9)) (reviewing EPA’s denial

of a petition to revise a NAAQS).

In my view, EPA has failed to satisfy this standard. Indeed,

reading the relevant sections of EPA’s petition denial—one

titled “No Mandatory Duty,” another “Different Policy

Approach,” and a third “Administration Global Climate Change

Policy,” see 68 Fed. Reg. at 52,929, 52,931—I find it difficult

even to grasp the basis for EPA’s action. In its brief, EPA

describes the petition denial as claiming that if the agency thinks

regulating GHGs is a bad idea, the Administrator has discretion

to withhold making a “judgment,” known as an “endangerment

finding,” that GHG emissions “cause, or contribute to, air

pollution which may reasonably be anticipated to endanger

public health or welfare,” see 42 U.S.C. § 7521(a)(1). Yet the

denial itself seems to rest more clearly (albeit still not clearly)

on a belief that even if the Administrator makes an

endangerment finding, that finding triggers no duty to set

emission standards. In the end, though, it makes no difference
24

whether one or both rationales are genuinely given in the

petition denial or whether they instead amount to post hoc

rescue attempts. As I explain below, neither rationale is

acceptable in light of section 202(a)(1)’s mandate.

EPA’s Discretion to Make an Endangerment Finding

In the petition denial, EPA states:

[T]he CAA provision authorizing regulation of motor

vehicle emissions does not impose a mandatory duty on the

Administrator to exercise her judgment. Instead, section

202(a)(1) provides the Administrator with discretionary

authority to address emissions . . . . While section 202(a)(1)

uses the word ‘shall,’ it does not require the Administrator

to act by a specified deadline and it conditions authority to

act on a discretionary exercise of the Administrator’s

judgment regarding whether motor vehicle emissions cause

or contribute to air pollution that may reasonably be

anticipated to endanger public health or welfare.

68 Fed. Reg. at 52,929. Expounding on this passage, EPA

argues in its brief that “[t]he ICTA Petition Denial reflects

EPA’s decision not to make any endangerment finding—either

affirmative or negative—under section 202(a)(1).” Resp’t Br.

at 62-63. In EPA’s view, “the Agency’s authority to make the

threshold finding is discretionary” and petitioners err in

suggesting that “if the statutory test for making the finding is

met, EPA has no choice but to set standards.” Id. at 57 (internal

quotation marks omitted). 

EPA’s brief also turns several policy concerns raised in

other portions of its petition denial into rationales for holding off

examining endangerment. These concerns include the

following: (1) “there continue to be important uncertainties in

our understanding of the factors that may affect future climate

change and how it should be addressed”; (2) petitioners
25

identified no technologies for reducing CH4, N2O, and HFC

emissions, and technologies for reducing CO2 emissions either

overlap with DOT’s authority or require further development;

(3) regulation “would also result in an inefficient, piecemeal

approach to addressing the climate change issue,” as the “U.S.

motor vehicle fleet is one of many sources of GHG emissions

both here and abroad”; (4) “[u]nilateral EPA regulation of motor

vehicle GHG emissions could also weaken U.S. efforts to

persuade key developing countries to reduce the GHG intensity

of their economies”; and (5) “EPA disagrees with the regulatory

approach urged by petitioners,” instead preferring “a number of

nonregulatory approaches to reducing GHG emissions” in line

with “the President’s global climate change policy” of

“support[ing] vital global climate research and lay[ing] the

groundwork for future action by investing in science,

technology, and institutions.” See 68 Fed. Reg. at 52,929-33.

EPA’s reasoning is simply wrong. In effect, EPA has

transformed the limited discretion given to the Administrator

under section 202—the discretion to determine whether or not

an air pollutant causes or contributes to pollution which may

reasonably be anticipated to endanger public health or

welfare—into the discretion to withhold regulation because it

thinks such regulation bad policy. But Congress did not give

EPA this broader authority, and the agency may not usurp it.

Section 202(a)(1)’s language—the “Administrator shall by

regulation prescribe . . . standards applicable to the emission of

any air pollutant from . . . new motor vehicles . . . which in his

judgment cause, or contribute to, air pollution which may

reasonably be anticipated to endanger public health or welfare,”

42 U.S.C. § 7521(a)(1)—establishes the limits of EPA’s

discretion. This section gives the Administrator the discretion

only to “judg[e],” within the bounds of substantial evidence,

whether pollutants “cause, or contribute to, air pollution which

may reasonably be anticipated to endanger public health or
26

welfare.” If conflicting credible evidence exists, e.g., some

evidence suggesting that GHGs may reasonably be anticipated

to endanger welfare and other evidence suggesting the opposite,

then the Administrator has discretion in weighing this evidence.

If the facts are known but require no single conclusion as to

whether a pollutant “may reasonably be anticipated to endanger

public health or welfare”—such as in a case where there exists

a small-to-moderate risk that a pollutant will cause a small-tomoderate amount of harm—then the Administrator has

discretion in assessing whether these facts amount to

endangerment. If the Administrator concludes based on

substantial evidence that more research is needed before he can

judge whether GHGs may reasonably be anticipated to endanger

welfare, then he has discretion to hold off making a finding. 

But section 202(a)(1) plainly limits the Administrator’s

discretion—his judgment—to determining whether the statutory

standard for endangerment has been met. The Administrator has

no discretion either to base that judgment on reasons unrelated

to this standard or to withhold judgment for such reasons. In

claiming otherwise, EPA not only ignores the statute’s language,

but also fails to reckon with this circuit’s related precedent.

Our en banc decision in Natural Resources Defense

Council, Inc. v. EPA, 824 F.2d 1146 (D.C. Cir. 1987), makes

clear that the Administrator may only exercise “judgment” in

evaluating whether the statutory standard has been met. There,

considering a CAA provision authorizing the Administrator to

set emission standards “at the level which in his judgment

provides an ample margin of safety to protect the public health,”

42 U.S.C. § 7412(b)(1)(B) (1982) (quoted in 824 F.2d at 1147),

we held that the Administrator had to base his determination on

what level would “provide an ‘ample margin of safety.’” See

824 F.2d at 1164-65. We struck down his proposed standards

because he failed to ground them in the statute. See id. at 1163-

64 (“[T]he Administrator has made no finding with respect to
27

the effect of the chosen level of emissions on health. . . .

Nowhere in the decision did the Administrator state that the

1976 emission standards provide an ‘ample margin of safety.’”).

Similarly, in Ethyl Corp. v. EPA, 541 F.2d 1 (D.C. Cir.

1976) (en banc), we considered whether EPA appropriately

linked its policy analysis to the statutory standard. That case

involved EPA’s decision to regulate leaded gasoline pursuant to

CAA section 211(c)(1)(A), 42 U.S.C. § 1857f-6c(1)(A) (1976),

currently codified as amended at 42 U.S.C. § 7545(c)(1)(A),

which at that time provided that the Administrator “may”

regulate fuel additives “if any emission products of such . . . fuel

additive[s] will endanger the public health or welfare.”

Determining that lead in gasoline presented “‘a significant risk

of harm’ to the public health,” 541 F.2d at 7, EPA regulated it.

Industry petitioners objected, claiming that the Administrator

needed “proof of actual harm rather than of ‘a significant risk of

harm.’” Id. at 12. Siding with EPA, we held that the agency

had discretion in determining what level of harm—or risk of

harm—constitutes endangerment. Id. We indicated that such

determinations involve policy issues, but—as Judge Randolph

neglects to mention, see op. of Randolph, J., at 13—these policy

issues all related to whether the statutory standard had been met,

i.e., to whether lead in gasoline endangered public health. See,

e.g., 541 F.2d at 24 (observing that “a determination of

endangerment to public health is necessarily a question of policy

that is to be based on an assessment of risks and that should not

be bound by either the procedural or the substantive rigor proper

for questions of fact”); id. at 26 (noting that “the statute accords

the regulator flexibility to assess risks and make essentially

legislative policy judgments”). Indeed, Ethyl makes quite clear

that the Administrator’s policy-based discretion is limited to the

terms of the statute. “All this is not to say that Congress left the

Administrator free to set policy on his own terms. To the

contrary, the policy guidelines are largely set, both in the

statutory term ‘will endanger’ and in the relationship of that
28

term to other sections of the Clean Air Act. These prescriptions

direct the Administrator’s actions.” Id. at 29; cf. Brown &

Williamson, 529 U.S. at 140 (noting that the FDA’s “judgment”

about how best to achieve public health goals is “no substitute

for the specific safety determinations required by the FDCA’s

various operative provisions”). 

In yet another case, Her Majesty the Queen in Right of

Ontario v. EPA, 912 F.2d 1525 (D.C. Cir. 1990), we held that

for EPA to decline to make an endangerment finding, it must

have a statutorily based reason for doing so. The CAA section

at issue provided that when the Administrator had “reason to

believe that any air pollutant or pollutants emitted in the United

States cause or contribute to air pollution which may reasonably

be anticipated to endanger public health or welfare in a foreign

country . . . , the Administrator shall give formal notice thereof

to the Governor of the State in which such emissions originate.”

Id. at 1527-28 (quoting 42 U.S.C. § 7415(a) (1982)) (omission

in original). Petitioners alleged that the Administrator acted

unreasonably in holding off making an endangerment finding as

to acid rain, which strong evidence (including informal EPA

statements) indicated was coming from the United States and

endangering Canadian welfare. Id. at 1529. We held that EPA

acted reasonably in postponing a formal endangerment finding

only because it gave a reasonable statutory basis for doing so.

Specifically, because EPA still lacked information as to which

states were causing the harmful acid rain, it would have been

“pointless” for the agency to make an endangerment finding

given the “specific [statutory] linkage between the

endangerment finding and the remedial procedures,” i.e.,

notifying offending states. Id. at 1533. “For this reason,” we

found EPA’s decision to postpone an endangerment finding

“both reasonable and consistent with the statute.” Id.

In short, EPA may withhold an endangerment finding only

if it needs more information to determine whether the statutory
29

standard has been met. Similarly, for EPA to find no

endangerment (as Judge Randolph, going beyond the agency’s

own arguments, appears to claim happened here, see op. of

Randolph, J., at 13, 15), it must ground that conclusion in the

statutory standard and may not rely on unrelated policy

considerations.

The statutory standard, moreover, is precautionary. At the

time we decided Ethyl, section 202(a)(1) and similar CAA

provisions either authorized or required the Administrator to act

on finding that emissions led to “air pollution which endangers

the public health or welfare.” See 42 U.S.C. § 1857f-1(a)(1)

(1976) (emphasis added). After Ethyl found that “the statutes

and common sense demand regulatory action to prevent harm,

even if the regulator is less than certain that harm is otherwise

inevitable,” Ethyl, 541 F.2d at 25 (emphasis added), the 1977

Congress not only approved of this conclusion, see H.R. Rep.

No. 95-294, at 49, but also wrote it into the CAA. Section

202(a)(1) (along with other provisions, see H.R. Rep. No. 95-

294, at 50) now requires regulation to precede certainty. It

requires regulation where, in the Administrator’s judgment,

emissions “contribute to air pollution which may reasonably be

anticipated to endanger public health or welfare.” 42 U.S.C. §

7521(a)(1) (emphasis added). As the House Report explained:

“In order to emphasize the precautionary or preventative

purpose of the act (and, therefore, the Administrator’s duty to

assess risks rather than wait for proof of actual harm), the

committee not only retained the concept of endangerment to

health; the committee also added the words ‘may reasonably be

anticipated to.’” H.R. Rep. No. 95-294, at 51 (emphasis added).

Given this framework, it is obvious that none of EPA’s

proffered policy reasons justifies its refusal to find that GHG

emissions “contribute to air pollution which may reasonably be

anticipated to endanger public health or welfare.” Unlike in Her

Majesty the Queen, EPA’s proffered reasons for refusing to
30

make an endangerment finding have no connection to the

statutory standard. Instead, as in Natural Resources Defense

Council (where we found EPA to have acted arbitrarily and

capriciously), EPA has “ventured into a zone of impermissible

action” by “simply substitut[ing]” freestanding policy concerns

for the sort of evaluation required by the statute. See 824 F.2d

at 1163. A look at these policy concerns proves the point. 

First, EPA claims that global warming still has many

scientific uncertainties associated with it. See 68 Fed. Reg. at

52,930-31; see also op. of Randolph, J., at 11-13. In this regard,

EPA makes much of the NRC’s statements that a link between

human-caused atmospheric GHG concentration increases and

this past century’s warming “cannot be unequivocally

established”; that “a wide range of uncertainty” remains

“inherent in current model predictions” due to imprecise

variables like future emissions rates, climate sensitivity, and the

forcing effects of aerosols; and that “current estimate [sic] of the

magnitude of future warming should be regarded as tentative

and subject to future adjustments (either upward or downward).”

See 68 Fed. Reg. at 52,930 (quoting NRC Rep. at 1, 17); see

also op. of Randolph, J., at 11-13. But the CAA nowhere calls

for proof. It nowhere calls for “unequivocal” evidence. Instead,

it calls for the Administrator to determine whether GHGs

“contribute to air pollution which may reasonably be anticipated

to endanger” welfare. EPA never suggests that the uncertainties

identified by the NRC Report prevent it from determining that

GHGs “may reasonably be anticipated to endanger” welfare. In

other words, just as EPA failed in Natural Resources Defense

Council to explain its chosen emissions level in light of the

statutory standard, so the agency has failed here to explain its

refusal to find endangerment in light of the statutory standard.

EPA’s silence on this point is telling. Indeed, looking at the

NRC Report as a whole, I doubt EPA could credibly conclude

that it needs more research to determine whether GHG-caused
31

global warming “may reasonably be anticipated to endanger”

welfare. Though not offering certainty, the report demonstrates

that matters are well within the “frontiers of scientific

knowledge,” see op. of Randolph, J., at 15 (quoting Envtl. Def.

Fund v. EPA, 598 F.2d 62, 82 (D.C. Cir. 1978)). The report also

indicates that the projected consequences of global warming are

serious. Because neither EPA nor Judge Randolph

acknowledges, let alone evaluates, these projected effects, I

quote the NRC’s discussion of the “Consequences of Increased

Climate Change of Various Magnitudes” in its entirety.

The U.S. National Assessment of Climate Change

Impacts, augmented by a recent NRC report on climate and

health, provides a basis for summarizing the potential

consequences of climate change. The National Assessment

directly addresses the importance of climate change of

various magnitudes by considering climate scenarios from

two well-regarded models (the Hadley model of the United

Kingdom and the Canadian Climate Model). These two

models have very different globally-averaged temperature

increases (2.7 and 4.4o C (4.9 and 7.9o F), respectively) by

the year 2100. A key conclusion from the National

Assessment is that U.S. society is likely to be able to adapt

to most of the climate change impacts on human systems,

but these adaptations may come with substantial cost. The

primary conclusions from these reports are summarized for

agriculture and forestry, water, human health, and coastal

regions. 

In the near term, agriculture and forestry are likely to

benefit from CO2 fertilization effects and the increased

water efficiency of many plants at higher atmospheric CO2

concentrations. Many crop distributions will change, thus

requiring significant regional adaptations. Given their

resource base, the Assessment concludes that such changes

will be costlier for small farmers than for large corporate
32

farms. However, the combination of the geographic and

climatic breadth of the United States, possibly augmented

by advances in genetics, increases the nation’s robustness

to climate change. These conclusions depend on the

climate scenario, with hotter and drier conditions increasing

the potential for declines in both agriculture and forestry.

In addition, the response of insects and plant diseases to

warming is poorly understood. On the regional scale and in

the longer term, there is much more uncertainty.

Increased tendency towards drought, as projected by

some models, is an important concern in every region of the

United States even though it is unlikely to be realized

everywhere in the nation. Decreased snow pack and/or

earlier season melting are expected in response to warming

because the freeze line will be moving to higher elevations.

The western part of the nation is highly dependent on the

amount of snow pack and the timing of the runoff. The

noted increased rainfall rates have implications for

pollution run-off, flood control, and changes to plant and

animal habitat. Any significant climate change is likely to

result in increased costs because the nation’s investment in

water supply infrastructure is largely tuned to the current

climate.

Health outcomes in response to climate change are the

subject of intense debate. Climate change has the potential

to influence the frequency and transmission of infectious

disease, alter heat- and cold-related mortality and

morbidity, and influence air and water quality. Climate

change is just one of the factors that influence the frequency

and transmission of infectious disease, and hence the

assessments view such changes as highly uncertain. This

said, changes in agents that transport infectious diseases

(e.g., mosquitoes, ticks, rodents) are likely to occur with

any significant change in precipitation and temperature.
33

Increases in mean temperatures are expected to result in

new record high temperatures and warm nights and an

increase in the number of warm days compared to the

present. Cold-related stress is likely to decline whereas

heat stress in major urban areas is projected to increase if

no adaptation occurs. The National Assessment ties

increases in adverse air quality to higher temperatures and

other air mass characteristics. However, much of the

United States appears to be protected against many different

adverse health outcomes related to climate change by a

strong public health system, relatively high levels of public

awareness, and a high standard of living. Children, the

elderly, and the poor are considered to be the most

vulnerable to adverse health outcomes. The understanding

of the relationships between weather/climate and human

health is in its infancy and therefore the health

consequences of climate change are poorly understood.

The costs, benefits, and availability of resources for

adaptation are also uncertain. 

Fifty-three percent of the U.S. population lives within

the coastal regions, along with billions of dollars in

associated infrastructure. Because of this, coastal areas are

more vulnerable to increases in severe weather and sea level

rise. Changes in storm frequency and intensity are one of

the more uncertain elements of future climate change

prediction. However, sea level rise increases the potential

damage to coastal regions even under conditions of current

storm intensities and can endanger coastal ecosystems if

human systems or other barriers limit the opportunities for

migration. 

In contrast to human systems, the U.S. National

Assessment makes a strong case that ecosystems are the

most vulnerable to the projected rate and magnitude of

climate change, in part because the available adaptation
34

options are very limited. Significant climate change will

cause disruption to many U.S. ecosystems, including

wetlands, forests, grasslands, rivers, and lakes. Ecosystems

have inherent value, and also supply the country with a

wide variety of ecosystem services.

The impacts of these climate changes will be

significant, but their nature and intensity will depend

strongly on the region and timing of the occurrence. At a

national level, the direct economic impacts are likely to be

modest. However, on a regional basis the level and extent

of both beneficial and harmful impacts will grow. Some

economic sectors may be transformed substantially and

there may be significant regional transitions associated with

shifts in agriculture and forestry. Increasingly, climate

change impacts will have to be placed in the context of

other stresses associated with land use and a wide variety of

pollutants. The possibility of abrupt or unexpected changes

could pose greater challenges for adaptation.

Even the mid-range scenarios considered in the IPCC

result in temperatures that continue to increase well beyond

the end of this century, suggesting that assessments that

examine only the next 100 years may well underestimate

the magnitude of the eventual impacts. For example a

sustained and progressive drying of the land surface, if it

occurred, would eventually lead to desertification of regions

that are now marginally arable, and any substantial melting

or breaking up of the Greenland and Antarctic ice caps

could cause widespread coastal inundation.

NRC Rep. at 19-20 (footnotes omitted). I have grave difficulty

seeing how EPA, while treating the NRC Report as an

“objective and independent assessment of the relevant science,”

68 Fed. Reg. at 52,930, could possibly fail to conclude that

global warming “may reasonably be anticipated to endanger

public health or welfare,” 42 U.S.C. § 7521(a)(1), with effects
35

on welfare including “effects on soil, water, crops, vegetation,

manmade materials, animals, wildlife, weather, visibility, and

climate, damage to and deterioration of property, and hazards to

transportation, as well as effects on economic values and on

personal comfort and well-being,” id. § 7602(h). It thus comes

as no surprise that EPA’s petition denial not only undertakes

none of the risk assessments described in Ethyl, 541 F.2d at 28

& n.58, but also utterly ignores the statutory standard.

EPA similarly fails to link its second policy

justification—that setting fuel economy standards represents the

only currently available way to regulate CO2 emissions and

petitioners “make no suggestion[s]” for how to reduce CH4,

N2O, and HFC emissions, 68 Fed. Reg. at 52,931—with the

statutory standard. As discussed earlier, supra at 21-22, the fact

that DOT sets fuel economy standards pursuant to the EPCA in

no way prevents EPA from setting standards pursuant to the

CAA. It is true that DOT has recently increased fuel economy

standards for light trucks, see 68 Fed. Reg. at 52,931; see also

op. of Randolph, J., at 14—a fact EPA did not even bother to

mention in its brief—but unless DOT’s action affects whether

GHGs “contribute to air pollution which may reasonably be

anticipated to endanger public health or welfare,” it provides no

support for EPA’s decision. 

As to EPA’s point about other GHGs, it may well be that no

current technologies exist for reducing their emissions. But

once again, this has nothing at all to do with the statutory

endangerment standard. Indeed, in section 202(a)(2), Congress

has made it crystal clear that endangerment findings must not

wait on technology.

Any regulation prescribed under paragraph (1) of this

subsection (and any revision thereof) shall take effect after

such period as the Administrator finds necessary to permit

the development and application of the requisite
36

technology, giving appropriate consideration to the cost of

compliance within such period.

42 U.S.C. § 7521(a)(2). As the Senate Report explained, EPA

“is expected to press for the development and application of

improved technology rather than be limited by that which

exists.” S. Rep. No. 91-1196, at 24 (1970); see also Natural

Res. Def. Council, Inc. v. EPA, 655 F.2d 318, 328 (D.C. Cir.

1981) (referencing this legislative history). In refusing to make

an endangerment finding because it lacks currently available

technology for controlling these emissions, EPA goes well

beyond the bounds of its statutory discretion.

EPA’s final policy reasons likewise fail. Because other

domestic and foreign sources contribute to atmospheric GHG

concentrations, GHG regulation might well “result in an

inefficient, piecemeal approach to addressing the climate change

issue,” 68 Fed. Reg. at 52,931. But again, Congress has

expressly demanded such an approach. Section 202(a)(1)

requires EPA to regulate if it judges that U.S. motor vehicle

emissions “cause, or contribute to, air pollution,” 42 U.S.C. §

7521(a)(1) (emphasis added); see also Ethyl, 541 F.2d at 29-31

(holding that the same language from section 211 plainly means

that emissions merit regulation even if they are not the only

source of air pollution). EPA (understandably) offers no basis

for thinking that U.S. automobile emissions are not contributing

to global warming. Indeed, why would the “Administration’s

global climate change policy plan support[] increasing

automobile fuel economy,” see 68 Fed. Reg. at 52,933, if motor

vehicle emissions were contributing nothing to global warming?

Similarly, EPA’s concern that regulation could weaken U.S.

negotiating power with other nations has nothing at all to do

with whether GHGs contribute to welfare-endangering air

pollution. Finally, while EPA obviously prefers nonregulatory

approaches to regulatory ones, see id. at 52,932-33, Congress

gave the Administrator discretion only in assessing whether
37

global warming “may reasonably be anticipated to endanger”

welfare, not “free[dom] to set policy on his own terms,” Ethyl,

541 F.2d at 29.

In short, EPA has utterly failed to relate its policy reasons

to section 202(a)(1)’s standard. Indeed, nowhere in its policy

discussion does EPA so much as mention this standard—“may

reasonably be anticipated to endanger public health or welfare.”

See 68 Fed. Reg. at 52,929-33 (the sections titled “Different

Policy Approach” and “Administration Global Climate Change

Policy”). EPA apparently dislikes the fact that section 202(a)(1)

says the Administrator “shall” regulate—rather than “may”

regulate—on making an endangerment finding. But EPA cannot

duck Congress’s express directive by declining to evaluate

endangerment on the basis of policy reasons unrelated to the

statutory standard. Although EPA is free to take its policy

concerns to Congress and seek a change in the Clean Air Act, it

must obey the law in the meantime.

EPA’s Discretion After Making an Endangerment Finding

Alternatively, EPA may have believed that even if it made

an endangerment finding, it had no obligation to regulate GHG

emissions. The petition denial states, 

EPA also disagrees with the premise of the petitioners’

claim—that if the Administrator were to find that GHGs, in

general, may reasonably be anticipated to endanger public

health or welfare, she must necessarily regulate GHG

emissions from motor vehicles. Depending on the

particular problem, motor vehicles may contribute more or

less or not at all. An important issue before the

Administrator is whether, given motor vehicles’ relative

contribution to a problem, it makes sense to regulate them.

. . . The discretionary nature of the Administrator’s section

202(a)(1) authority allows her to consider these important

policy issues and decide to regulate motor vehicle
38

emissions as appropriate to the air pollution problem being

addressed. Accordingly, even were the Administrator to

make a formal finding regarding the potential health and

welfare effects of GHGs in general, section 202(a)(1) would

not require her to regulate GHG emission from motor

vehicles.

68 Fed. Reg. at 52,929. This passage is puzzling. Motor

vehicles emit GHGs in significant quantities, see U.S. Dep’t of

State, U.S. Climate Action Report 2002, at 40—a point EPA

nowhere contests. The statute clearly states that the

Administrator “shall by regulation prescribe . . . standards”

governing the emissions of air pollutants from motor vehicles if

the Administrator makes an endangerment finding regarding

these pollutants. 42 U.S.C. § 7521(a)(1) (emphasis added).

Compare id. § 7545(c)(1)(A) (using “may”). Refusing to

regulate following an endangerment finding would violate the

law. Indeed, EPA appears to have abandoned this argument. In

a (rare) concession to the Act’s text, EPA counsel acknowledged

at oral argument, “I don’t think that we would contest that if the

agency had made an endangerment finding, that then you would

have to give some significance to the term ‘shall’ in [section]

202(a).” Tr. of Oral Arg. at 44.

V.

Although this case comes to us in the context of a highly

controversial question—global warming—it actually presents a

quite traditional legal issue: has the Environmental Protection

Agency complied with the Clean Air Act? For the reasons given

above, I believe that EPA has both misinterpreted the scope of

its statutory authority and failed to provide a statutorily based

justification for refusing to make an endangerment finding. I

would thus grant the petitions for review.