Geoscience Reference
In-Depth Information
The list could go on and on. While these debates may seem like amus-
ing distractions, they pose serious challenges because of their impact on
public opinion. So in this fi nal part, I discuss the hurdles that confront
climate-change policy today.
THE MEANING OF SCIENTIFIC CONSENSUS
Suppose you are a student assigned to write a paper on the role of
humans in global climate change. In light of the dueling advocates on
both sides, you want to determine what scientists believe. When you
look at Wikipedia, you fi nd the following: “Presently the scientifi c con-
sensus on climate change is that human activity is very likely the cause
for the rapid increase in global average temperatures over the past sev-
eral decades. Consequently, the debate has largely shifted onto ways to
reduce further human impact and to fi nd ways to adapt to change that
has already occurred.”
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So at the very beginning, you are told that there is a scientifi c con-
sensus. A little bell might go off in your head. What is a scientifi c con-
sensus? How can we decide whether there is one? Who decides? Aren't
there cases of past consensuses that turned out to be wrong?
A scientifi c consensus is the collective judgment of the community
of informed and knowledgeable scientists in a particular fi eld at a given
time. But determining the “collective judgment” is very tricky. Science
does not proceed by majority rule. There are no votes on scientifi c prin-
ciples, and most scientists would scoff at the idea that science is decided
by a plebiscite. Moreover, we know that even the most brilliant scien-
tists have sometimes taken a wrong turn.
One way to identify a consensus is to examine authoritative text-
topics and expert reports on the subject. Let's take an example of the
concept of externalities, which is critical for understanding the eco-
nomics of climate change. We might turn to the fi ne introductory text-
book by distinguished Princeton economists William Baumol and
Alan Blinder, now in its eleventh edition. They actually list externali-
ties as one of the “10 Great Ideas” of economics. Here is what they write:
“Some transactions affect third parties who were not involved in the
decision. . . . Such social costs are called
externalities
because they af-
