Hot or not? Developing a spectrum of indicator-based assessments in approaching vulnerability to climate change

ABSTRACT Vulnerability assessments to climate change are instruments to support the design of mitigation and adaptation strategies. They are relevant to cities or regions where the impacts may be significant and politicians are keen to avoid economic losses due to maladaptation or inefficient policy courses. Despite the relative simplicity of indicator-based assessments (IbAs), their reliability has been questioned due to their non-robustness and inconsistent outcomes due to changes in modelling assumptions. Nonetheless, politicians still require evidence-based tools to make decisions to signal adaptation and policy approaches. This article develops a range of IbAs through the Ordered WeightedAverage (OWA) approach to construct a decision space for policy-makers. The OWA incorporates the possibility of non-robustness and inconsistency, and improves our understanding about vulnerability. We take Auckland, New Zealand, as a case study and find that if policymakers are risk averse, policy focus is on minimising vulnerability to coastal inundation due to sea level rise. As policymakers ease risk aversion, focus switches to enhancing natural capital and ecosystem services. The OWA reveals the trade-offs prevalent in complex socio-ecological systems and coupled human-infrastructure systems. Therefore, it consolidates a knowledge base for decision-making, which could be adapted internationally and create knowledge spillover and exchange of expertise.