Types of Future Climate Scenarios
The most common scenario type is based on outputs from climate models and is emphasized here. Three other types usually have been applied with reference to or in conjunction with model-based scenarios: incremental scenarios for sensitivity studies, analogue scenarios, and a general category of “other scenarios”. The origins of these scenarios and their mutual linkages are depicted in Figure 2.
Figure 2: Alternative data sources and procedures for constructing climate scenarios for use in impact assessment.
The suitability of each type of scenario for use in policy-relevant impact assessment can be evaluated according to five criteria:
- Regional level consistency with global projections. Scenario changes in regional climate may lie outside the range of global mean changes but should be consistent with theory and model-based results.
- Physical plausibility and realism. Changes in climate should be physically plausible, such that changes in different climatic variables are mutually consistent and credible.
- Appropriateness of information for impact assessments. Scenarios should present climate changes at an appropriate temporal and spatial scale, for a sufficient number of variables, and over an adequate time horizon to allow for impact assessments.
- Representativeness of the potential range of future regional climate change.
- Accessibility. The information required for developing climate scenarios should be readily available and easily accessible for use in impact assessments.
A summary of the major advantages and disadvantages of different scenario development methods, based on these criteria, is presented in IPCC Table 13.1 21
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