Human displacements from tropical cyclone Idai attributable to climate change

Abstract

Extreme weather events often trigger massive population displacement. A compounding factor is that the frequency and intensity of such events is affected by anthropogenic climate change. However, the effect of historical climate change on displacement risk has so far not been quantified. Here, we show how displacement can be partially attributed to climate change, using the example of the 2019 tropical cyclone Idai in Mozambique. We estimate population exposure to flooding following Idai’s landfall, using a combination of storm surge modeling and flood depth estimation from remote sensing images, for factual (climate change) and counterfactual (no climate change) mean sea level and maximum wind speed conditions. We find that climate change has increased displacement risk from this event by approximately 3.1 to 3.5%, corresponding to 16,000 - 17,000 additional displaced persons. Besides highlighting the significant effects on humanitarian conditions already imparted by climate change, our study provides a blueprint for event-based displacement attribution.

Designing and describing climate change impact attribution studies: a guide to common approaches

“…The non-probabilistic approach to event impact attribution focuses solely on how different forcings contribute to the scale of the event's observed impacts. This includes the storyline approach, which has only had limited application to impact attribution so far; for example, one recent study used this approach to examine the scale of displaced populations resulting from Tropical Cyclone Idai (Mester et al, 2022). By simulating the extent of flooding that would have resulted from the cyclone, with and without the contribution of anthropogenic forcing to the event, the authors were able to estimate that at least 16,000 additional persons were displaced.…”