An article by three prominent economists* in the New York Times this week summarized the Climate Leadership Council’s Conservative Case for Climate Action“. The “four pillars” of this climate plan include (1) a revenue-neutral tax on carbon emissions, which are used to fund… (2) quarterly “carbon dividend” payments to all Americans; (3) border tax adjustments to account for carbon emissions and carbon taxes abroad; (4) eliminating all other regulations on emissions of carbon. The “Case” is thus a shift from traditional environmental regulation to a policy based on tax incentives, then wrapped around a redistributive universal income mechanism.

I’ll dispense with the latter “feature” by referencing my recent post on the universal basic income: bad idea! The economists advocate for the carbon dividend sincerely, but also perhaps as a political inducement to the left and confused centrists.

The Limits of Our Knowledge

The most interesting aspect of the “Case” is how it demonstrates uncertainty around the wisdom of carbon restrictions of any kind: traditional regulations, market-oriented trading, or tax incentives. Those all involve assumptions about the extent to which carbon emissions should be restricted, and it’s not clear that any one form of restriction is more ham-handed than another. Traditional regulation may restrict output in various ways. For example, standards on fuel efficiency are an indirect way of restricting output. A carbon market, with private trading in assigned “rights” to emit carbon, is more economically efficient in the sense that a tradeoff is involved for any decision having carbon implications at the margin. However, the establishment of a carbon market ultimately means that a limit must be imposed on the total quantity of rights available for trading.

A carbon tax imputes a cost of carbon emissions to society. It also imposes tradeoffs, so it is similar to carbon trading in being more economically efficient than traditional regulation. A producer can attempt to adjust a production process such that it emits less carbon, and the incidence of the tax falls partly on final consumers, who adjust the carbon intensity of their behavior accordingly. For our purposes here, a tax is more illuminating in the sense that we can assess inputs to the cost imputation. Even a cursory examination shows that the cost estimate can vary widely given reasonable differences in the inputs. So, in a sense, a tax helps to reveal the weakness of the case against carbon and the carbon-based rationale for allowing a coercive environmental authority to sclerose the arteries of the market system.

The three economists propose an initial tax of $40 per metric ton of emitted carbon. The basis for that figure is the so-called “social cost of carbon” (SCC), a theoretical construct that is not readily measured. Economists have long subscribed to the theory of social costs, or negative externalities, and to the legitimacy of government action to force cost causers to internalize social costs via corrective taxation. However, the wisdom of allowing the state to intrude upon markets in this way depends on our ability to actually measure specific external costs.

Fatuous Forecasts

The SCC is based on the presumed long-run costs of an incremental ton of carbon in the environment. I do not use the word “presumed” lightly. The $40 estimate subsumes a variety of speculative assumptions about the climate’s response to carbon emissions, the future economic impact of that response, and the rate at which society should be willing to trade those future costs against present costs. The figure only counts costs, without considering the huge potential benefits of warming, should it actually occur.

Ronald Bailey at Reason illustrates the many controversies surrounding the calculation of the SCC. He notes the tremendous uncertainty surrounding an Obama Administration estimate of $36 a ton in 2007 dollars. It used an outdated climate sensitivity figure much higher than more recent estimates, which would bring the calculated SCC down to just $16.

A discount rate of 3% was applied to projected future carbon costs to produce an SCC in present value terms. The idea is that today’s “collective” would be indifferent between paying this cost today and suffering the burden of future costs inflicted by carbon emissions. This presumes that 3% is the expected return society can earn for the future by investing resources today. Unfortunately, the SCC is tremendously sensitive to the discount rate. Together with the more realistic estimate of climate sensitivity, a discount rate of 7% (the Office of Management and Budget’s regulatory guidance) would actually make the SCC negative!

Another U.S. regulatory standard, according to Bailey, is that calculations of social cost are confined to costs borne domestically. However, the SCC attempts to encompass global costs, inflating the estimate by a factor of 4 to 14 times. The justification for the global calculation is apparent righteousness in owning up to the costs we cause as a nation, and also for the example it sets for other countries in crafting their own carbon policies. Unfortunately, it also magnifies the great uncertainties inherent in this messy calculation.

Lack of Evidence

This guest essay on the Watts Up With That? web site by Paul Driessen and Roger Bezdek takes a less gracious view of the SCC than Bailey, if that is possible. As they note, in addition to climate sensitivity, the SCC must come to grips with the challenge of measuring the economic damage caused by each degree of warming. This includes factors far into the future that simply cannot be projected with any confidence. We are expected to place faith in distant cost estimates of heat-related deaths, widespread crop failures, severe storm damage, coastal flooding, and many other calamities that are little more than scare stories. For example, the widely reported connection between atmospheric carbon concentration and severe weather is demonstrably false, as are reports that Pacific islands have been swallowed by the sea due to global warming.

Ignoring the Benefits

The SCC makes no allowance for the real benefits of burning fossil fuels, which have been a powerful engine of economic growth and still hold the potential to lift the underdeveloped world out of poverty and environmental  distress. The benefits of carbon also include fewer cold-related deaths, higher agricultural output, and a greener environment. It isn’t surprising that these benefits are ignored in the SCC calculation, as any recognition of that promise would undermine the narrative that fossil fuels are unambiguously evil. Indeed, an effort to calculate only the net costs of carbon emissions would likely expose the entire exercise as a sham.

The “four pillars” of the Climate Leadership Council‘s case for climate action rest upon an incredibly flimsy foundation. Like anthropomorphic climate change itself, appropriate measurement of a social cost of carbon is an unsettled issue. Its magnitude is far too uncertain to use as a tool of public policy: as either a tax or a rationale for carbon regulation of any kind. And let’s face it, taxation and regulation are coercive acts that better be undertaken with respect for the distortions they create. In this case, it’s not even clear that carbon emissions should be treated as an external cost in many applications, as opposed to an external benefit. So much for the corrective wisdom of authorities. The government is not well-equipped to centrally plan the economy, let alone the environment.

• The three economists are Martin Feldstein, Ted Halstead and Greg Mankiw.