Fathom, a global expert in water risk intelligence, has produced what are said to be the most accurate predictions to date for flooding risks under climate change.
Published in Water Resources Research, the study compared current inland and coastal flood risks with forecasts for the years 2050 and 2100, examining both an optimistic low-emissions scenario (SSP1-2.6) and a pessimistic high-emissions scenario (SSP5-8.5). The optimistic scenario is achievable only if all global carbon reduction targets are fully realized.
The findings reveal that under the low-emissions scenario, flood hazards are projected to increase by a median of 9% by 2100 compared to 2020, with possible outcomes ranging from a 6% decrease to a 29% increase. Conversely, the high-emissions scenario predicts a much steeper rise in flood risks, with an expected 49% increase by the century’s end, and a potential range from a 7% to 109% increase.
Near-term projections up to 2050 show smaller increases in flood hazards, with a 7% rise under the low-emissions scenario and 15% under the high-emissions scenario. These scenarios exhibit significant overlap in their likely outcomes by 2050, with the low scenarios ranging between a 7% decrease and a 26% increase, and the high scenarios ranging between a 5% decrease and a 43% increase. After 2050, the divergence between the scenarios becomes more pronounced.
Coastal flooding is expected to continue rising in both scenarios due to the delayed response of the oceans to existing warming. Even under the optimistic low-emissions scenario, coastal flood risks could increase by 99% by 2100.
The most significant increases in flooding are anticipated along global coastlines, in tropical Africa and Asia, and in the arid regions of North Africa, though these projections carry a high degree of uncertainty. Greater certainty in flood risk increases exists along the North Atlantic and Indian Ocean coasts, as well as in Southeast Asia and the Pacific Islands.
The study also underscored the considerable uncertainties that remain in climate forecasting, largely due to the lack of data for benchmarking, insufficient flood defence information, and unavoidable errors resulting from missing data.
Representing a major leap forward in global flood modelling, the research built on nearly a decade of advancements in flood inundation models. These models have improved significantly in resolution, physical accuracy, and the integration of climate change data, enabling more precise estimates of population exposure, asset risk, flood defence cost-benefit analysis, and future loss projections.
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