Has Climate Change Worsened the Flooding Caused by Cyclone Idai in Mozambique?
In March 2019, Tropical Cyclone Idai struck Mozambique and caused devastating flooding. A new scientific approach shows how climate change amplified these disasters. Researchers analyzed the influence of three main factors: rising sea levels, increased wind intensity, and heavier rainfall.
The rise in sea levels and stronger winds mainly increased material damage. These factors increased the damage by 6 to 27 percent compared to a scenario without global warming. However, their impact on the extent and volume of flooding remains limited, with an increase of only 0.1 to 0.8 percent. Conversely, the more intense rainfall, linked to the current climate, mainly expanded the flooded areas and increased the volume of water by 5 to 19 percent. Yet, their contribution to destruction remains modest, between 2 and 8 percent.
When these three factors act together, the damage reaches its highest level, with an increase of up to 35 percent. This is explained by a complex relationship between the intensity of flooding and its consequences. A stronger flood does not always result in a larger flooded area, but it can destroy more infrastructure and housing.
Tropical cyclones like Idai often combine multiple causes of flooding: heavy rainfall, river flooding, and coastal storm surges. These events are difficult to study using traditional methods, as they depend on many factors such as terrain, land use, and the condition of watersheds. Poor and vulnerable regions, such as those in East Africa, often lack the data needed to assess these risks. Yet, they bear the full brunt of climate change effects.
Scientists used a method called “scenario attribution.” This approach does not merely calculate probabilities but examines how each climate factor separately influences flooding and its impacts. This method provides a better understanding of the mechanisms at play, even in areas where information is scarce.
The findings highlight the importance of studying all the causes to measure the real impact of climate change. Prevention and adaptation policies could thus more effectively target the most exposed populations. This method could be applied to other regions of the world regularly affected by cyclones. It offers a valuable tool to address the lack of analysis in the least equipped countries.
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Cited Study
DOI: https://doi.org/10.5194/nhess-26-1417-2026
Title: Climate and impact attribution of compound flooding induced by tropical cyclone Idai in Mozambique
Journal: Natural Hazards and Earth System Sciences
Publisher: Copernicus GmbH
Authors: Doris M. Vertegaal; Bart J. J. M. van den Hurk; Anaïs Couasnon; Natalia Aleksandrova; Tycho Bovenschen; Fernaldi Gradiyanto; Tim W. B. Leijnse; Henrique M. D. Goulart; Sanne Muis