What are the implications of sea-level rise for a 1.5, 2 and 3 \xb0C rise in global mean temperatures in the Ganges-Brahmaputra-Meghna and other vulnerable deltas?

Sally Brown,Sugata Hazra,Robert J Nicholls,Kwasi Appeaning Addo,Duncan D Hornby,Chris Hill,Attila N Lázár,John Caesar,Emma L Tompkins,Anisul Haque

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, 2.0 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 0.07 and 0.09 m when temperatures are projected at 3.0 °C compared with 1.5 °C. In unprotected areas, the depth of flooding is projected to increase by approximately 50% to 0.21–0.27 m, 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 datasets of elevation.

Highlights

The Paris Agreement (United Nations 2015) aims for temperature stabilisation to ‘well below 2 °C above pre-industrial levels’ and pursue ‘efforts to limit the temperature increase to 1.5 °C’
This study has assessed the impacts of sea-level rise (SLR) at temperatures equivalent to 1.5, 2.0 and 3.0 °C in coastal Bangladesh and the wider implications for other vulnerable deltas
The immediate effects of a 1.5 °C rise in temperature on the sea level may be relatively small, but sea-level rise will have an important legacy in delta regions

Summary

Introduction

The Paris Agreement (United Nations 2015) aims for temperature stabilisation to ‘well below 2 °C above pre-industrial levels’ and pursue ‘efforts to limit the temperature increase to 1.5 °C’. There is limited understanding of the impacts of SLR at 1.5 and 2.0 °C in vulnerable low-lying deltas This paper analyses the implications of temperature and equivalent SLR at 1.5, 2.0 and 3.0 °C in the world’s largest delta which is highly populated, the GangesBrahmaputra-Meghna (GBM), plus the wider implications for other deltas. This will be achieved by (i) reviewing the setting of the GBM; (ii) describing the modelling methodology used; (iii) analysing impacts at 1.5, 2.0 and 3.0 °C; and (iv) discussing the caveats and consequences of these findings in the context of other deltas, plus the potential for adaptation

Methods

Results

Conclusion