Storylines for CCIAV studies (see Box 2.1) are increasingly adopting a multi-sectoral and multi-stressor approach (Holman et al., 2005a, b) over multiple scales (Alcamo et al., 2005; Lebel et al., 2005; Kok et al., 2006a; Westhoek et al., 2006b) and are utilising stakeholder elicitation (Kok et al., 2006b). As they have become more comprehensive, the increased complexity and richness of the information they contain has aided the interpretation of adaptive capacity and vulnerability (Metzger et al., 2006). Storyline development is also subjective, so more comprehensive storylines can have alternative, but equally plausible, interpretations (Rounsevell et al., 2006). The concept of a ‘region’, for example, may be interpreted within a storyline in different ways - as world regions, nation states, or sub-national administrative units. This may have profound implications for how storylines are characterised at a local scale, limiting their reproducibility and credibility (Abildtrup et al., 2006). The alternative is to link a locally sourced storyline, regarded as credible at that scale, to a global scenario.
Storylines can be an endpoint in their own right (e.g., Rotmans et al., 2000), but often provide the basis for quantitative scenarios. In the storyline and simulation (SAS) approach (Alcamo, 2001), quantification is undertaken with models for which the input parameters are estimated through interpretation of the qualitative storylines. Parameter estimation is often subjective, using expert judgement, although more objective methods, such as pairwise comparison, have been used to improve internal consistency (Abildtrup et al., 2006). Analogues and stakeholder elicitation have also been used to estimate model parameters (e.g., Rotmans et al., 2000; Berger and Bolte, 2004; Kok et al., 2006a). Moreover, participatory approaches are important in reconciling long-term scenarios with the short-term, policy-driven requirements of stakeholders (Velázquez et al., 2001; Shackley and Deanwood, 2003; Lebel et al., 2005).