2.3.2. What are the Appropriate Scales of Analysis for Impact Assessments?
Climate change impact assessments must begin with decisions about the scope
and scale of the assessment: What are the main policy issues? What and who are
exposed to climate change impacts? What is the appropriate scaletime frame,
geographical extent, and resolution? Considerable progress has been achieved
since the SAR in raising such framing questions at the outset of an assessment
cycle, often in conjunction with representative stakeholders (see Carter et
al., 1994; Downing et al., 2000).
Methods for identifying policy issues include checklists and inventories, document
analysis, surveys and interviews, and simulations. The process of determining
the scope of assessment should be iterative. The project design should specify
what and who is exposed to climate change impactseconomic sectors, firms,
or individuals. Evaluation of adaptation strategies should be cognizant of actors
involved in making decisions or suffering consequences.
The choice of temporal scales, regional extent, and resolution should be related
to the focus of the assessment. Often, more than one scale is required, under
methods such as strategic scale cycling (Root and Schneider, 1995) or multi-level
modeling (e.g., Easterling et al., 1998). Linkage to global assessments
may be necessary to understand the policy and economic context (e.g., Darwin
et al., 1995).
The most common set of methods and tools remains various forms of dynamic simulation
modeling, such as crop-climate models or global vegetation dynamic models. A
major improvement in impact modeling has been applicaton of process-oriented
models, often with geographically explicit representations, instead of models
that are based on correlations of climatic limits. Data for running and validating
models is a recurrent issue. Intermodel comparisons have been undertaken in
some areas (e.g., Mearns et al., 1999), but much remains to be done.
Climate change is likely to have multiple impacts across sectors and synergistic
effects with other socioeconomic and environmental stresses, such as desertification,
water scarcity, and economic restructuring. Most studies (especially as reported
in the SAR) have focused on single-sector impacts. Relatively few studies have
attempted to integrate regionally or even identified segments of the population
that are most at risk from climate change.
Vulnerability assessment may be one way of integrating the various stresses
on populations and regions arising from climate change (see Briguglio, 1995;
Clark et al., 1998; Huq et al., 1999; Kaly et al., 1999; Mimura
et al., 2000; Downing et al., 2001). There are some areas in which formal
methods for vulnerability assessment have been well developed (e.g., famine
monitoring and food security, human health) and applied to climate change. However,
methods and tools for evaluating vulnerability are in formative stages of development.
Further development of methods and tools for vulnerability assessment appears
warranted, especially for the human dimensions of vulnerability, integration
of biophysical and socioeconomic impacts, and comparison of regional vulnerability.
Conceptual models and applications of the evolution of vulnerability on the
time scale of climate change are required. Formal methods of choosing indicators
and combining them into meaningful composite indices must be tested. Combining
qualitative insight and quantitative information is difficult but essential
to full assessments. Finally, improved methods and tools should facilitate comparison
of vulnerability profiles between at-risk regions and populations and highlight
potential reductions in vulnerability, through policy measures or the beneficial
effects of climate change.