Climate risk assessment: a literature review and the formulation of a model hierarchy

Assessing climate change risk represents a urgent and complex challenge. This thesis presents a comprehensive literature review on climate risk assessment, evaluating the current state of the art and formulating a model hierarchy to improve the usability and practical application of climate risk science. The review focuses on three key natural hazards — river floods, heatwaves and droughts — at global scale. The analysis reveals that while hazard modeling is well-established, showing notable differences in approach across different hazard types, the exposure model shows moderate consistency, with variations primarily driven by the choice of risk metric. In contrast, vulnerability remains the least represented and most inconsistently modeled risk determinant. To address these challenges, this thesis provides a structured interpretation of the reviewed studies and introduces a framework that organizes the modeling processes into six interconnected modules. From the findings of the review, here a novel hierarchy of climate risk models is proposed. Following an interpretation of model complexity based on the dynamism of its components, this hierarchy aligns with the literature goal of simplifying complex systems and enhancing process understanding. An analytical definition of three categories of models gives the hierarchy an interesting direction on its possible applications, providing a systematic approach to selecting and applying models for different research and policy needs, addressing the demand for usable science in climate risk assessment. The work also acknowledges the limitations of this proposal and possible future developments. The framework and hierarchy proposed in this thesis presents substantial potential to advance climate risk research and to shape effective strategies to mitigate the widespread impacts of climate change. However, further research is essential to realize and refine these contributions.