Benefits of climate change mitigation for reducing the impacts of sea-level rise in G-20 countries

This paper assesses the potential benefits of climate-change mitigation in reducing the impacts of sea-level rise over the 21st century in G-20 countries (excluding the European Union as a whole), using the Dynamic Interactive Vulnerability Assessment model. Impacts of the expected number of people flooded annually and wetland losses were assessed. To assess the benefits of mitigation, it was assumed that defences were not upgraded during the study. Globally, with a sea-level rise of 0.68 m by the 2080s (with respect to 1980–99), representing a potential future with limited climate-change mitigation, and with the Special Report on Emissions Scenarios A1 socio-economic scenario, 123 million additional people could be flooded annually and 39% of present global wetland stock could be lost. For a 0.19-m rise in sea level, associated with a substantial reduction in emissions, the number of people flooded could be reduced to 13 million/y, with 21% of global wetland stock loss, unless new wetlands emerge. Collectively, non-Annex 1 G-20 countries experience a disproportionately higher number of people flooded in their nations compared with the proportion of population flooded globally. The greatest wetland losses for G-20 countries are projected for Australia, Indonesia, and the United States. Thus, G-20 nations with the highest emissions or gross domestic product frequently do not experience the greatest impacts, despite some of these nations being potentially more able to pay for adaptation.