A well-documented rise in global temperatures has coincided with a significant increase in the concentration of carbon dioxide in the atmosphere. Respected scientists believe the two trends are related. For when carbon dioxide is released into the atmosphere, it acts like the ceiling of a greenhouse, trapping solar energy and retarding the escape of reflected heat. It is therefore a species—the most important species— of a “greenhouse gas.” Calling global warming “the most pressing environmental challenge of our time,” a group of states, local governments, and private organizations, alleged . . . [that the] EPA has abdicated its responsibility under the Clean Air Act to regulate the emissions of four greenhouse gases, including carbon dioxide. Specifically, petitioners asked us to answer two questions concerning . . . the Act: whether EPA has the statutory authority to regulate greenhouse gas emissions from new motor vehicles; and if so, whether its stated reasons for refusing to do so are consistent with the statute.
I Section 202(a)(1) of the Clean Air Act . . . provides:
The [EPA] Administrator shall by regulation prescribe (and from time to time revise) . . . 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. . . . The Act defines “air pollutant” to include “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.” “Welfare” is also defined broadly: among other things, it includes “effects on . . . weather . . . and climate.”
II On October 20, 1999, a group of 19 private organizations filed a rulemaking petition asking EPA to regulate “greenhouse gas emissions from new motor vehicles under Section 202 of the Clean Air Act.” . . . As to EPA’s statutory authority, the petition observed that the agency itself had already confirmed that it had the power to regulate carbon dioxide. In 1998, Jonathan Z. Cannon, then EPA’s General Counsel, prepared a legal opinion concluding that “CO emissions are within the scope of EPA’s authority to regulate,” even as he recognized that EPA had so far declined to exercise that authority. Cannon’s successor, Gary S. Guzy, reiterated that opinion before a congressional committee just two weeks before the rulemaking petition was filed.
EPA has refused to comply with this clear statutory command. Instead, it has offered a laundry list of reasons not to regulate. For example, EPA said that a number of voluntary executive branch programs already provide an effective response to the threat of global warming, that regulating greenhouse gases might impair the president’s ability to negotiate with “key developing nations” to reduce emissions, and that curtailing motor-vehicle emissions would reflect “an inefficient, piecemeal approach to address the climate change issue.” Although we have neither the expertise nor the authority to evaluate these policy judgments, it is evident they have nothing to do with whether greenhouse gas emissions contribute to climate change. Still less do they amount to a reasoned justification for declining to form a scientific judgment. . . . Nor can EPA avoid its statutory obligation by noting the uncertainty surrounding various features of climate change and concluding that it would therefore be better not to regulate at this time. If the scientific uncertainty is so profound that it precludes EPA from making a reasoned judgment as to whether greenhouse gases contribute to global warming, EPA must say so. That EPA would prefer not to regulate greenhouse gases because of some residual uncertainty . . . is irrelevant. The statutory question is whether sufficient information exists to make an endangerment finding. In short, EPA has offered no reasoned explanation for its refusal to decide whether greenhouse gases cause or contribute to climate change. Its action was therefore “arbitrary, capricious, . . . or otherwise not in accordance with law.” . . . [Reversed and remanded.]
1. Under what conditions did the Supreme Court say it had the power to reverse the EPA’s decision not to regulate the carbon dioxide emissions of new vehicles?
2. What did the petitioners, including the State of Massachusetts, want the EPA to do?
3. The EPA said that, even if it had the authority to regulate greenhouse gas emissions from motor vehicles, it would not do so. What reasons did the EPA give for this refusal? What did the Supreme Court say about those reasons?
4. Following this decision of the Supreme Court, what was the EPA required to do? Was the EPA required to set a standard for greenhouse gas emissions from new vehicles?
5. Look back at the discussion about proving causation at the start of Part Two of this chapter. Did the Supreme Court say that greenhouse gas emissions from vehicles caused global warming? What did the Court observe about causation?