Idai flood modelling finds a larger climate effect in deeper water
A peer-reviewed study revisits the people exposed to Mozambique’s 2019 cyclone flooding. Comparing historical climate and settlement conditions, the model finds that warming has a modest effect on the flooded area but a larger influence on exposure to deep water. In the model, population growth and shifts in where people live contribute more strongly to the overall increase in exposure.
Science··Midday
Climate influence rises with water depth
For people living near Beira, a coastal city in Mozambique, the depth of flooding changes the scale of exposure to Cyclone Idai. A single peer-reviewed modelling study of the 2019 storm estimates that climate change enlarged the flooded area by about 2 per cent. Its relative contribution to population exposure reached approximately 3 per cent, 13 per cent and 24 per cent across successively deeper water categories. The calculation counts people within flooded zones, rather than measuring deaths or financial losses.[1]
Historical comparisons hold the storm track fixed
Four scenarios combine conditions for climate and population, using 1975 as the historical comparison. The recent scenario pairs the storm’s climate with the 2020 settlement distribution, the closest population dataset available. Rainfall, wind and sea level change between climate scenarios while the observed storm track stays fixed. About a quarter of a million people occupy the modelled flood area under recent conditions. Growth and redistribution of population contribute more to the overall exposure increase than climate change does.[1]
Poorer groups start with greater deep-water exposure
Wealthier groups have a larger proportional increase in exposure to very deep water, yet poorer groups face more of that exposure before the climate adjustment. These differences depend on where groups live. Socioeconomic characteristics were assessed separately, using limited spatial data, so the findings describe broad population patterns. The estimates remain conditional on this storm, the selected depth categories and assumptions about vulnerability.[1]
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