222 Weighingthe uncertainty
in the global context, might form the basis of appropriate political and
economic response to climate change. The rest of this chapter and the
following chapters will draw heavily on their work.Narrowing the uncertainty
A key question constantly asked by policymakers is, ‘How long will it be
before scientists are more certain about the projections of likely climate
change, in particular concerning the regional and local detail?’ They were
asking that question over a decade ago and then I generally replied that in
ten to fifteen years we would know a lot more.As we saw in the first sec-
tion of this chapter, over the past decade a lot of progress in knowledge has
been made. There is more confidence that anthropogenic climate change
has been detected and more confidence too in climate change projections
than was the case a decade ago. However, some of the key uncertainties
remain and their reduction is urgently needed. Not surprisingly,
policymakers are still asking for more certainty. What can be done to
provide it?
For the science of change, the main tools of progress are observations
and models. Both need further development and expansion. Observations
are required to detect climate change in all its aspects as it occurs and
also to validate models. That means that regular, accurate and consistent
monitoring of the most important climate parameters is required with
good coverage in both space and time. Monitoring may not sound very
exciting work, often even less exciting is the rigorous quality control
that goes with it, but it is absolutely essential if climate changes are
to be observed and understood. Because of this, a major international
programme, the Global Climate Observing System (GCOS) has been set
up to orchestrate and oversee the provision of observations on a global
basis. Models are needed to integrate all the scientific processes that are
involved in climate change (most of which are non-linear, which means
they cannot be added together in any simple manner) so that they can
assist in the analysis of observations and provide a method of projecting
climate change into the future.
Take, for instance, the example of cloud radiation feedback that re-
mains the source of greatest single uncertainty associated with climate
sensitivity.^5 It was mentioned in Chapter 5 that progress with understand-
ing this feedback will be made by formulating better descriptions of cloud
processes for incorporation into models and also by comparing model
output, especially of radiation quantities, with observations especially
those made by satellites. To be really useful such measurements need
to be made with extremely high accuracy – to within the order of 0.1%