It is hot. It is humid. Even sound intellects have trouble maintaining focus in the dog days of Beltway August, a phenomenon illustrated recently by my esteemed colleague and good friend, Mark J. Perry. An absolutely solid economist. AEI scholar. University of Michigan professor. General Secretary of Carpe Diem, hands down the most useful and interesting policy blog anywhere. A gentleman. A scholar. Bon vivant.

Letting nuclear power help to reduce Green House Gas (GHG) emissions really is a benefit/cost question of investment in nuclear generation versus gas-fired plants moving forward. REUTERS/Petr Josek

And: nuclear power enthusiast, despite the underlying unfavorable economics. As any good economist would, Mark implicitly tries to make a “social cost” (or “externality”) argument to justify the higher costs of nuclear power and the subsidies needed to make it competitive, about which more below. Mark criticizes, correctly, the hypocrisy of the environmental left as it condemns fuel use that emits greenhouse gases (GHG) even as it attempts to shut down the nuclear power industry, which produces electricity emitting no GHG at all. Nor does nuclear power generation emit other effluents. (The nuclear waste issue from a technological standpoint is trivial, a topic for another day.) That is what leads Mark to argue that electric utilities should be required to purchase “zero-emission credits from [nuclear] plants.” That is: Nuclear power should be subsidized by the ratepayers.

Competition of ideas | Read Perry’s piece here: Let Nuclear Power Play a Role in Reducing Greenhouse Gas Emissions

Where to begin? Mark seems to believe that “zero-carbon” electricity matters. First—as an aside—the term “carbon” is political propaganda, as carbon dioxide is a colorless, odorless gas a certain minimum atmospheric concentration of which is necessary for life itself. It is not “carbon,” which is soot, or in the language of environmental policy, particulate matter, which is a pollutant and the emissions of which are regulated by a series of other rules promulgated by the Environmental Protection Agency. (The EPA seems to believe that the economically optimal emissions level for particulates approaches zero, a fundamental analytic error, and, again, a topic for another day.)

By far the most important GHG in terms of the radiative properties of the troposphere is water vapor; does anyone call it a “pollutant?” Of course not; but the reason cannot be that ocean evaporation is a natural process while anthropogenic emissions of other GHG are not. After all, volcanic eruptions are natural phenomena, but no one claims that the massive resulting emissions of particulates, mercury, and other toxins are not pollutants. The use of the phrase “air pollution” in this context is intended by the environmental left to cut off debate before it begins by assuming the answer to the underlying policy question. I urge Mark and all serious observers of energy markets to employ the term GHG, which has the virtue of being accurate scientifically without doing so.

Mark fails to ask whether the substitution of “carbon-free” electricity in place of fossil-fired generation would matter. Suppose that all U.S. electricity generation were “carbon-free.” What would the effect be in terms of global temperatures in the year 2100, using the EPA’s climate model? U.S. emissions of GHG from power generation in 2015 were about 1.9 billion metric tons, roughly 5 percent of total emissions of GHG worldwide. The answer: less than six one-thousandths of a degree, under assumptions that exaggerate the effects of the GHG reductions, an effect that would not be measurable in that the standard deviation of the surface temperature record is about one tenth of a degree, for 1980-2015. (Thanks to Chip Knappenberger for this latter computation.)

And so: What is that microscopic temperature effect worth? Zero, to be blunt, although the EPA in its remarkable dishonesty would disagree: It is the reduction in GHG emissions alone that counts, times the purported “social cost of carbon,” regardless of the actual climate effects of the reductions. But Mark, in his references to “zero-carbon” electricity, fails to ask that fundamental question. Put aside the myriad problems with the “renewable” electricity cost estimates published by the Energy Information Administration: For new nuclear power plants, the “levelized” cost of power production (loosely, spread evenly over the life of the generation facilities) is about $100 per megawatt-hour (mWh). For natural gas combined cycle power plants, it is about $56.

So what would justify investment in expensive nuclear power in place of cheap gas-fired electricity? Mark does not quite tell us; but he implies that avoidance of the non-GHG emissions of pollutants from the latter (the required purchase of “zero-emission credits from [nuclear] plants”) might be a rationale.

Note that gas-fired and other conventional forms of electricity already are subjected to an array of environmental protection requirements that have the effect of reducing such effluents sharply. Accordingly, unless Mark wants to argue that these emissions controls are insufficient (that is, inefficiently lax), the regulatory policies have “internalized” the social costs of the pollutants in the relevant sense that they equate the marginal benefits and costs of reduced pollution, however crudely by the political market trading off the benefit of reduced pollution with the cost of achieving it.

Now, Mark is quite correct that it is nutty to shut down operating nuclear plants: Their operating costs (after capital costs already have been incurred) are only about $11 per mWh, while the comparable figure for gas-fired plants is about $41. And Mark is correct to note the utter dishonesty of the anti-nuclear political crowd, which has failed to offer a coherent (or, indeed, any) rationale for shutting down nuclear generating stations that have been operating safely for years, other than a vague but loud argument to the effect that nuclear power is “bad.” (Mark’s implicit point that the shutdown of San Onofre units 2 and 3 in southern California is all cost and no benefit is not quite correct: There appears to have been a design flaw resulting in some real operational problems and safety concerns, a fix for which was not obviously efficient in terms of costs.)

But Mark’s larger point—let nuclear power help to reduce GHG emissions—really is a benefit/cost question of investment in nuclear generation versus gas-fired plants moving forward. There simply is no evaluation of the cost data or GHG effects under any set of reasonable assumptions that can favor the former.

Benjamin Zycher is the John G. Searle Scholar at the American Enterprise Institute.