Brown, Sally, Nicholls, Robert J., Lazar, Attila N., Hornby, Duncan D., Hill, Chris, Hazra, Sugata, Addo, Kwasi Appeaning, Haque, Anisul, Caesar, John and Tompkins, Emma L. (2018) What are the implications of sea-level rise for a 1.5°C, 2°C and 3°C rise in global mean temperatures in the Ganges-Brahmaputra-Meghna and other vulnerable deltas? Regional Environmental Change. (doi:10.1007/s10113-018-1311-0).
Abstract
Even if climate change mitigation is successful, sea levels will keep rising. With subsidence, relative sea-level rise represents a long-term threat to low-lying deltas. A large part of coastal Bangladesh was analysed using the Delta Dynamic Integrated Emulator Model to determine changes in flood depth, area and population affected given sea-level rise equivalent to global mean temperature rises of 1.5°C, 2.0°C and 3.0°C with respect to pre-industrial for three ensemble members of a modified A1B scenario.
Annual climate variability today (with approximately 1.0°C of warming) is potentially more important, in terms of coastal impacts, than an additional 0.5°C warming. In coastal Bangladesh, the average depth of flooding in protected areas is projected to double to between 0.07m to 0.09m when temperatures are projected at 3.0°C compared with 1.5°C. In unprotected areas, depth of flooding is projected to increase by approximately 50% to 0.21-0.27m, whilst the average area inundated increases 2.5 times (from 5% to 13% of the region) in the same temperature frame. The greatest area of land flooded is projected in the central and north-east regions. In contrast, lower flood depths, less land area flooded and fewer people are projected in the poldered west of the region.
Over multi-centennial timescales, climate change mitigation and controlled sedimentation to maintain relative delta height are key to a delta’s survival. With slow rates of sea-level rise, adaptation remains possible, but further support is required. Monitoring of sea-level rise and subsidence in deltas is recommended, together with improved data sets of elevation.
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