Using uncertain sea level rise projections : adaptation in Rotterdam and New York

Melissa Sapuan's (MS '12) thesis explored coastal cities, where much of the world's population and economic activity is concentrated, are vulnerable to sea level rise and other impacts of climate change. While there has been increased attention on taking action to reduce the adverse impacts of climate change at the city-scale, one of the obstacles local authorities face is the inherent uncertainty in climate change projections. This thesis examined how Rotterdam and New York, two leading cities in climate change adaptation, used sea level rise projections in their adaptation plans and addressed the issue of uncertainty. These case studies showed that cities adopt different processes to obtain local sea level rise projections, influenced by their institutional and political structures. Rotterdam leveraged on projections and adaptation planning at the national level, while New York commissioned its own city-level climate change risk assessment and focused largely on adaptation policies that are to be implemented at the city level. Despite the emphasis in the literature on the role of science-based climate change impact assessments as the basis for adaptation planning, the case studies suggest that the inherent uncertainties in climate change science limit the usefulness of the specific projections from such assessments for adaptation planning. However, many adaptation strategies that cities could adopt require only a broad understanding of the potential local impacts of sea level rise and information about current conditions. To be prepared for future sea level rise, cities should consider alternative assessment approaches that are less dependent on specific sea level rise projections. They should also consider building in flexibility for adjustment in their adaptation policies and explore innovative design responses to variable and uncertain sea levels.