Community vulnerability assessments elicit knowledge from community members, who have intimate knowledge of their local surroundings. In contrast, expert judgment is a means of soliciting informed opinions from individuals with particular expertise. This approach is often used to obtain a rapid assessment of the state of knowledge concerning particular aspects of climate change. Expert judgment is most effective when used in a panel format, bringing together experts with a range of experience and/or opinions.
Expert judgment has been used in a variety of different ways. In developed country studies, expert judgment is often used to validate the findings of vulnerability and impact assessments, or indicators, or studies that attempt to place boundaries on what constitutes adaptation, or the thresholds of dangerous climate change (Brooks and Adger, 2005; Doria et al, 2009; Arnell et al, 2005; Smith et al, 2009).
There are also some examples of expert judgment forming the key method, or being integral to the creation of an assessment. Alberini et al (2006) used conjoint choice questions of public health and climate change experts to determine which of two hypothetical countries (described by a vector of seven socio-economic and health attributes) they deemed to have the higher adaptive capacity. Probit models indicated that respondents viewed per capital income, inequality in the distribution of income, universal health care coverage, and high access to information as important determinants of adaptive capacity. They then used the estimated coefficients and country socio-demographics to construct an index of adaptive capacity for several countries. In panel data regressions, this index proved to be a good predictor of mortality in climate disasters, thereby affirming that expert judgment is an important method in vulnerability and impact assessments. Similarly a complex vulnerability assessment in France and Portugal combined multiple ecosystem services and their values as perceived by multiple stakeholders, finding that different stakeholders differ in their vulnerability to land-use change; for example farmers and conservation agency groups (common to both sites), or hunters in Portugal and hikers in France (de Chazal et al, 2008).
A potential explanation offered for the differential vulnerabilities in Portugal and France is also often cited as a criticism of stakeholder participation methods – that vulnerability is strongly contextual. Despite its widespread use and evidence for utility, caution has been expressed over the use of expert judgment as a method for climate impact and vulnerability assessments. Those of the positivist vein, who prioritise empirical and quantitative data in the interests of comparability, warn against its potentially subjective nature (Fuessel, 2007). Even the way experts understand climate change and its risks is subjective, and thus the way they bring their knowledge to bear in expert judgment methods is laden with their values and understanding of climate and social systems in eliciting such discourses (Lowe and Lorenzoni, 2007).
