Geoscience Reference
In-Depth Information
One of the strangest claims of contrarians is the third argument:
“The fact is that CO
2
is not a pollutant.” What might this mean? Pre-
sumably, it means that CO
2
is not by itself toxic to humans or other organ-
isms within the range of concentrations that we are likely to encounter,
and indeed higher CO
2
concentrations may be benefi cial.
However, this is not the meaning of pollution under U.S. law or in
standard economics. The U.S. Clean Air Act defi nes an air pollutant as
“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.” In a 2007 decision
on this question, the Supreme Court ruled on the question: “Carbon
dioxide, methane, nitrous oxide, and hydrofl uorocarbons are without a
doubt 'physical [and] chemical . . . substance[s] which [are] emitted
into . . . the ambient air.' . . . Greenhouse gases fi t well within the Clean
Air Act's capacious defi nition of 'air pollutant.' ”
17
In economics, a pollutant is a form of negative externality—that
is, a by-product of economic activity that causes damages to innocent
bystanders. The question here is whether emissions of CO
2
and other
greenhouse gases will cause net damages, now and in the future. I re-
viewed this question in Chapter 20, and it may be useful to look back at
the results shown in Figure 8. Eleven of the thirteen studies concluded
that there are net damages, and the damages rise sharply for warming
side effect of economic activity.
In their fi nal point, the sixteen scientists argued that warming
might be benefi cial. In doing so, they cited my earlier work and claimed
that my studies showed that policies to slow climate change would be
unnecessary for the next half century: “A recent study of a wide variety
of policy options by Yale economist William Nordhaus showed that
nearly the highest benefi t-to-cost ratio is achieved for a policy that al-
lows 50 more years of economic growth unimpeded by greenhouse gas
controls. . . . And it is likely that more CO
2
and the modest warming
that may come with it will be an overall benefi t to the planet.”
The fi rst problem with this claim is an elementary mistake in eco-
nomic analysis. The authors use the concept of the “benefi t-to-cost ratio”
