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5.4. Integrated Assessment of Potential Vulnerabilities and Impacts
In the foregoing sections, impact categories have been treated separately.
Obviously, however, the impacts of climate change interact with one another-through
the use of resources such as water and land and through economy, society, and
politics. An integrated assessment tries to take these interactions into account.
In addition, an integrated assessment tries to compare the diversity of impacts
with respect to their seriousness (from a human viewpoint) and evaluate overall
vulnerability to climate change.
Three approaches to integrated assessment have been applied to Europe: monetization,
integrated modeling, and coupled models and expert panels. Each method has its
advantages and disadvantages, which are discussed at length in Weyant et al.
(IPCC 1996, WG III, Chapter 10). The focus here is on the results. Note, however,
that integrated assessment is a young field, without a great number of well-established
methodologies, let alone results.
5.4.1. Integrated Assessment Using Monetization
One way of integrating the range of potential impacts of climate change is
to derive a comprehensive monetary estimate, which adds all impacts expressed
in their dollar value. This approach allows for comparison of the seriousness
of climate change with other problems, comparison of vulnerabilities to climate
change among regions and sectors, and comparison of the impact of climate change
with the impact of greenhouse gas emission reduction. Expressing effects on
marketed goods and services (e.g., land loss resulting from sea-level rise,
energy savings in winter) in monetary terms is relatively straightforward because
the price is known. Expressing damage to nonmarketed goods and services (e.g.,
wetland loss, mortality changes) in monetary terms can be accomplished by examining
market transactions where such goods or services are implicitly traded (e.g.,
landscape beauty) or by interviewing people about their preferences. That is,
human preferences are expressed by people's willingness to pay to secure a benefit
or their willingness to accept compensation for a loss. In western Europe, valuation
techniques are well established and widely applied. Numerous theoretical and
empirical problems remain, however. Based on the SAR (IPCC 1996, WG II, Chapter
6), Fankhauser and Tol (1997) report best estimates for the annual impact resulting
from a doubling of atmospheric concentrations of carbon dioxide of about -1.6%
to -1.4% of the GDP in western Europe, using a mix of earlier GCM scenarios
standardized to a 2.5°C increase in the global mean temperature. Best estimates
for eastern Europe and the former Soviet Union vary between -0.4% and +0.4%
(a benefit) of GDP. These figures compare with an estimated world impact of
-1.8% to -1.2% of GDP. National differences may be hidden by the regional average,
but only one country-specific study has been carried out to date. Using similar
methods and scenarios as Fankhauser and Tol (1997), Kuoppomaeki (1996a, b) concludes
that Finland may gain about 1% of GDP. Many assumptions underlie these best
guesses; the uncertainties are large, yet unknown.
5.4.2. Integrated Assessment Using Integrated Modeling
An integrated assessment model combines climate change scenarios with models
of various impacts of climate change in a single computer code (i.e., hard-linking
of models). One advantage of this approach is that consistency is ensured (e.g.,
land or water used for agriculture is not used in the domestic sector). A disadvantage
is that modeling and computational requirements entail simplifications of the
state-of-the-art. Only two integrated assessment models are even somewhat useful
for climate change impact assessment in Europe; the other twenty-odd models
reviewed in IPCC (1996, WG III, Chapter 10) have other aims or are based on
monetization. The first integrated assessment model is the ESCAPE model (Rotmans
et al., 1994), which was developed specifically for the EU. It includes a variety
of impacts on natural and human systems; since its completion in 1991, however,
the model has not been updated. The second such model is the IMAGE2 model (Alcamo,
1994). This model is up-to-date. It models the whole world, with a focus on
land use. The resolution is 0.5°x0.5°, with east and west Europe grouped into
two economic regions. The socioeconomic modeling of agriculture and human infrastructure-the
dominant land-use tupes in Europe-requires further work.
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