Heat vulnerability assessment: A systematic review of critical metrics

Research on heat vulnerability provides a scientific foundation for identifying heatwave-sensitive areas and vulnerable populations, thereby enabling targeted climate adaptation. Standardizing and refining metric selection is crucial for constructing effective heat vulnerability assessment systems. To boost the precision of heat vulnerability assessments, this research explores current limitations in metric selection. We systematically reviewed metrics from 31 studies across environmental, demographic, and socioeconomic dimensions. Our analysis reveals three main challenges: variations in indicator selection, classification, and processing; correlations between indicators and regional characteristics; and inter-metric correlations of conceptual redundancy and oversimplification. These discrepancies and deficiencies may affect the robustness of assessments and increase the difficulty of subsequent discussions, diminishing the policy relevance. Our review identifies and summarizes context-specific indicators, highlights issues of metric redundancy and oversimplification along with corresponding solutions, and establishes guidelines for metric selection. This facilitates the selection of concise, representative metrics for developing more accurate heat vulnerability indices, ultimately enabling targeted interventions to mitigate heatwave impacts.