A natural hazard risk modelling approach to human displacement - frontiers & challenges

Simona Meiler

Extreme weather is increasingly driving human displacement worldwide, a trend expected to worsen with climate change. Quantifying global displacement risk is thus crucial for assessing potential impacts and informing long-term strategies to build more resilient societies, and reducing this risk. One approach involves leveraging classic probabilistic risk modelling methods that hinge on the interplay of hazard, exposure, and vulnerability. Here, we present a methodological stocktaking of these natural-hazard risk models as applied to human displacement. Specifically, we present a globally consistent displacement risk model from multiple hazards under present-day and future conditions. We model population displacement from tropical cyclone winds, coastal floods, river floods, and droughts under present, optimistic, and pessimistic future climate conditions for the middle and end of the century, assuming constant exposure and vulnerability. Our results reveal that current displacement risk is on the order of 30 million annual average displacements (AAD). By 2100, global displacement risk could increase by 75% (157%) under optimistic (pessimistic) climate scenarios. While our risk model makes methodological advances through its global setup, utilisation of two risk frameworks and state-of-the-art datasets, we also highlight current challenges in displacement risk modelling. For instance, our approach primarily models displacement as the direct result of loss of homes from sudden-onset hazards. While we begin to incorporate indirect drivers, such as livelihood loss in river floods and droughts, the model still omits important social, political, and economic dimensions. Nevertheless, as our model adopts a modular design, continuous updates enable the inclusion of additional hazards, improved data, and integration of these broader dimensions. This stocktaking represents a concerted research effort, and our modelling framework may help inform global discussions in international climate negotiations, including those related to Loss and Damage, national action plans, policy development, and other climate adaptation strategies, provided appropriate data and context are applied.

Figure: Global, multi-hazard, present-day displacement risk. Annual average displacement (AAD) estimates for the four hazards (tropical cyclone wind, coastal flood, river flood, and drought) combined are displayed at the admin1 level. Areas in grey indicate zero values; areas in white indicate no data.