Quantifying Land and People Exposed to Sea-Level Rise with No Mitigation and 1.5°C and 2.0°C Rise in Global Temperatures to Year 2300

We use multiple synthetic mitigation sea-level scenarios, together with a non-mitigation sea-level scenario from the Warming Acidification and Sea-level Projector model. We find sea-level rise (SLR) continues to accelerate post-2100 for all but the most aggressive mitigation scenarios indicative of 1.5 degrees C and 2.0 degrees C. Using the Dynamic Interactive Vulnerability Assessment modeling framework, we project land and population exposed in the 1 in 100year coastal flood plain under SLR and population change. In 2000, the flood plain is estimated at 540 x 10(3) km(2). By 2100, under the mitigation scenarios, it ranges between 610 x 10(3) and 640 x 10(3) km(2) (580 x 10(3) and 700 x 10(3) km(2) for the 5th and 95th percentiles). Thus differences between the mitigation scenarios are small in 2100. However, in 2300, flood plains are projected to increase to between 700 x 10(3) and 960 x 10(3) km(2) in 2300 (610 x 10(3) and 1290 x 10(3) km(2)) for the mitigation scenarios, but 1630 x 10(3) km(2) (1190 x 10(3) and 2220 x 10(3) km(2)) for the non-mitigation scenario. The proportion of global population exposed to SLR in 2300 is projected to be between 1.5% and 5.4% (1.2%-7.6%) (assuming no population growth after 2100) for the aggressive mitigation and the non-mitigation scenario, respectively. Hence over centennial timescales there are significant benefits to climate change mitigation and temperature stabilization. However, sea-levels will continue to rise albeit at lower rates. Thus potential impacts will keep increasing necessitating adaptation to existing coastal infrastructure and the careful planning of new coastal developments. Plain Language Summary If we reduce greenhouse gas emissions and stabilize global temperatures, sea-level rise (SLR) will continue at a reduced rate for centuries. This is because changes to the ocean and cryosphere (ice) which contribute to SLR take very long timescales to respond to changes in global warming. Early and aggressive climate change mitigation will be most effective to reduce flood risk, particularly after the 21st century. Even with climate change mitigation, the land area exposed to coastal flooding will continue to increase for centuries. Adapting the coast to cope with rising sea levels is inevitably required. The long-term implications for coastal habitation need to be considered.