When we hear about "clean" energy these days, it generally refers only to solar and wind, which do not emit CO2.  CO2 is never mentioned as a "criteria pollutant" in the Clean Air Act or any amendment.  Yet in 2007, the Supreme Court of the United States, in a 5-4 decision in the case of Massachusetts v. EPA, declared CO2 a Clean Air Act pollutant.  I wonder how many have noticed the possibility of a constitutional conflict here.

I note that the designation of "clean energy" evidently does not cover nuclear (or hydro), although these also do not emit CO2 in generating electricity.  The reason seems to be mainly ideological.  Climate alarmists illogically prefer solar and wind, in spite of their well recognized erratic nature and intermittency – requiring (fossil-fueled, CO2-emitting) standby power plants on the electric grid.  These must always be ready to fill any unacceptable supply gaps "when the Sun don't shine and the wind don't blow."  A federal investment tax credit and other subsidies also favor S&W in spite of their many shortcomings.

But CO2 is not a pollutant by any stretch of the imagination.  CO2 is a natural constituent of Earth's atmosphere and a vital fertilizer for all growing plants.  Without atmospheric CO2, there would be no agriculture and indeed no life on Earth.  Its putative impact on the climate is minor.  For example, I have shown that CO2 has no definitive influence on sea level rise – even though plaintiff Massachusetts claimed fear of massive inundation to establish "legal standing" in its lawsuit against the EPA.

I must note, however, that the plaintiffs' evidence may be tainted; it is based solely on an affidavit supplied by Prof. Michael Oppenheimer, a former chief scientist of the Environmental Defense Fund, an aggressive non-profit group.

Other problems of treating CO2 as a pollutant

Once the Supreme Court announced its decision, EPA issued its notorious Endangerment Finding, claiming CO2 is harmful to "human health and welfare."  In accordance with Clean Air Act, the EPA ambitiously applied its Endangerment Finding to fossil-fueled electric power plants, thus providing a scientific and legal rationale for President Obama's "Clean Power Plan," through which he had promised to "bankrupt" coal-fired power plants.

The lawsuit before the Supreme Court actually involved CO2 emissions from motor vehicles rather than power plants.  I will just recuse myself at this point and leave further discussion to lawyers – in particular, whether the EPA is encroaching on the National Highway Traffic Safety Administration in the Department of Transportation, which is responsible for setting mileage efficiency standards for motor vehicles.

I would just note that since the EPA decided to adopt the Clean Air Act as a guide, it has evaded its legal mandate to control all CO2 emissions by applying an arbitrary (i.e., not authorized by law) modification to the Clean Air Act in the form of a "tailoring rule" for cars, trucks, etc.  Thereby, the EPA exempted from regulation such small CO2 sources, despite their central role in the lawsuit that saw the Supreme Court ascribing pollutant status to CO2.

Conclusion

Evidently, the Clean Air Act is not suited for the regulation of CO2.  This is perhaps a job for a future Congress.  Nuclear is superior in most respects to solar and wind energy; it appears to be the energy source for the future, after we deplete low-cost fossil fuel deposits.

I hope that the Supreme Court will revisit its 2007 decision soon.  In writing the minority dissent, Justice Scalia perceptively questioned both the legal standing of the plaintiff and the uncertain science underlying the majority decision.

S. Fred Singer is professor emeritus at the University of Virginia and director of the Science & Environmental Policy Project.  His specialty is atmospheric and space physics.  An expert in remote sensing and satellites, he served as the founding director of the U.S. Weather Satellite Service and, more recently, as vice chair of the U.S. National Advisory Committee on Oceans & Atmosphere.  He is a senior fellow of the Heartland Institute and the Independent Institute.  He co-authored the N.Y. Times bestseller "Unstoppable Global Warming: Every 1500 years."