Some global economics 237Integrated Assessment and Evaluation^14
In the assessment and evaluation of the impacts of
different aspects of global climate change with its
large complexity, it is essential that all components
are properly addressed. The major components are
illustrated in Figure 1.5. They involve a very wide
range of disciplines from natural sciences, technol-
ogy, economics and the social sciences (including
ethics). Take the example of sea level rise – probably
the easiestimpact to envisage and to quantify. From
the natural sciences, estimates can be made of the
amount and rate of rise and its characteristics. From
various technologies, options for adaptation can be
proposed. From economics and the social sciences,
risks canbe assessed and evaluated. Theeconomic
costs of sea level rise might be expressed, for in-
stance, most simply as the capital cost of protection
(where protection is possible) plus the economic
value of the land or structures that may be lost
plus the cost of rehabilitating those persons that
could be displaced. But in practice the situation is
more complex. For a costing to be at all realistic,
especially when it is to apply to periods of decades
into the future, it must account not only for direct
damage and the cost of protection but also for a
range of options and possibilities for adaptation
other than direct protection. The likelihood of in-
creased storm surges with the consequent damages
and the possibility of substantial loss of life need
also to be addressed. Further, there are other indi-
rect consequences; for instance, the loss of fresh
water because of salination, the loss of wetlands
and associated ecosystems, wildlife or fisheries
and the lives and jobs of people that would be af-
fected in a variety of ways. In developed country
situationsrough estimates of the costs of some of
these components can be made in money terms.
For developing countries, however, the possible
options can less easily be identified or weighed
and even rough estimates of costs cannot be
provided.
Integrated Assessment Models or IAMs are im-
portant tools for Integrated Assessment and Evalu-
ation. They represent within one integrated numer-
ical model the physical, chemical and biological
processes that control the concentration of green-
house gases in the atmosphere, the physical pro-
cesses that determine the effect of changing green-
house gas concentrations on climate and sea level,
the biology and ecology of ecosystems(natural and
managed), the physical and human impacts of cli-
mate change and the socio-economics of adaptation
to and mitigation of climate change. Such models
are highly sophisticated and complex although
their components are bound to be very simplified.
They provide an important means for studying the
connections and interactions between the various
elements of the climate change problem. Because
of their complexity and because of the non-linear
nature of many of the interactions, a great deal of
care and skill is needed in interpreting the results
from such models.
A number of the components of impact, even
for the relatively simple situation of sea level rise,
cannot be readily costed in money terms. For in-
stance, the loss of ecosystems or wildlife as it
impacts tourism can be expressed in money terms,
but there is no agreed way of setting a money mea-
sure for the longer-term loss or the intrinsic value
of unique systems. Or a further example is that,
although the cost of rehabilitationfor displaced
people can be estimated, other social, security or
political consequences of displacement (e.g. in ex-
treme cases the loss of whole islands or even whole
states) cannot be costed in terms of money. Any
appraisal therefore of impacts of anthropogenic cli-
mate change will have to draw together components
that are expressed in different ways or use different
measures. Policy and decision makers need to find
ways of considering alongside each other all the
components that need to be aggregated in order to
make appropriate judgements.^15