Chapter 9
Weighing the uncertainty
This bookis intended to present clearly the current scientific position
on global warming. A key part of this presentation concerns the uncer-
tainty associated with all parts of the scientific description, especially with
the prediction of future climate change, which forms an essential con-
sideration when decisions regarding action are being taken. However,
uncertainty is a relative term; utter certainty is not often demanded on
everyday matters as a prerequisite for action. Here the issues are com-
plex; we needto consider how uncertainty is weighed against the cost
of possible action. First of all we address the scientific uncertainty.
The scientific uncertainty
Before considering the ‘weighing’ process and the cost of action, we
begin by explaining the nature of the scientific uncertainty and how it
has been addressed by the scientific community.
In earlier chapters I explained in some detail the science underly-
ing the problem of global warming and the scientific methods that are
employed for the prediction of climate change due to the increases in
greenhouse gases. The basic physics of the greenhouse effect is well
understood. If atmospheric carbon dioxide concentration doubles and
nothing else changes apart from atmospheric temperature, then the av-
erage global temperature near the surface will increase by about 1.2◦C.
That figure is not disputed among scientists.
However, the situation is complicated by feedbacks and regional
variations. Numerical models run on computers are the best tools avail-
able for addressing these problems. Although they are highly complex,
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