Global projections of river flood risk in a warmer world

• Published in: Earth's future Vol. 5; no. 2; pp. 171 - 182
• Main Authors: Alfieri, Lorenzo, Bisselink, Berny, Dottori, Francesco, Naumann, Gustavo, Roo, Ad, Salamon, Peter, Wyser, Klaus, Feyen, Luc
• Format: Journal Article
• Language: English
• Published: Hoboken, USA Wiley Periodicals, Inc 01.02.2017; John Wiley & Sons, Inc
• Subjects: Agreements; Atmospheric models; Basins; Climate change; Computer simulation; Emergency communications systems; Environmental policy; Environmental risk; Flood control; Flood damage; flood frequency; Flood risk; Floods; Future climates; General circulation models; Global climate; Global temperatures; Global warming; Hazards; Hydrologic models; Hydrology; Impact analysis; International agreements; International organizations; model agreement; Paris Agreement; Population; rcp 8.5; Risk; Risk assessment; River networks; Rivers; Socioeconomic factors; Socioeconomics; specific warming levels; Statistical analysis; Stream discharge; Stream flow; France, Paris; INW, Asia; ANE, Europe; Africa
• ISSN: 2328-4277; 2328-4277
• DOI: 10.1002/2016EF000485

Rising global temperature has put increasing pressure on understanding the linkage between atmospheric warming and the occurrence of natural hazards. While the Paris Agreement has set the ambitious target to limiting global warming to 1.5°C compared to preindustrial levels, scientists are urged to explore scenarios for different warming thresholds and quantify ranges of socioeconomic impact. In this work, we present a framework to estimate the economic damage and population affected by river floods at global scale. It is based on a modeling cascade involving hydrological, hydraulic and socioeconomic impact simulations, and makes use of state‐of‐the‐art global layers of hazard, exposure and vulnerability at 1‐km grid resolution. An ensemble of seven high‐resolution global climate projections based on Representative Concentration Pathways 8.5 is used to derive streamflow simulations in the present and in the future climate. Those were analyzed to assess the frequency and magnitude of river floods and their impacts under scenarios corresponding to 1.5°C, 2°C, and 4°C global warming. Results indicate a clear positive correlation between atmospheric warming and future flood risk at global scale. At 4°C global warming, countries representing more than 70% of the global population and global gross domestic product will face increases in flood risk in excess of 500%. Changes in flood risk are unevenly distributed, with the largest increases in Asia, U.S., and Europe. In contrast, changes are statistically not significant in most countries in Africa and Oceania for all considered warming levels. Key Points Global flood risk assessment at different warming levels based on ensemble climate projections At 4°C warming 70% of the world population and GDP will face increase in flood impact over 500% Projected changes in flood risk are largest in Asia, America, and Europe Plain Language Summary At the Paris Agreement, 195 countries set the ambitious target to limiting global warming to 1.5°C compared to pre‐industrial levels. This appears in contrast with the latest trends recording warming in the range of 1°C and a relentless increase towards higher levels. Scientists are urged to quantify the socio‐economic impacts of natural hazards under different degrees of global warming. This research presents the first global assessment of economic damage and population affected by river floods under different global warming scenarios. We used an ensemble of high‐resolution climate projections to derive streamflow simulations in the present and in the future climate. Those were analyzed to assess the frequency and magnitude of river floods and their impacts under future scenarios corresponding to 1.5, 2, and 4°C global warming. Results indicate a clear relation between atmospheric warming and future flood risk in most world regions. At 4°C warming, countries representing more than 70% of the global population and global GDP will face increases in flood risk in excess of 500%. Projected increase in flood risk is largest in Asia, America and Europe. In contrast, projected changes have low confidence in most countries in Africa and Oceania for all considered warming levels.