Abstract
Estimates of changes in the frequency or height of contemporary extreme
sea levels (ESLs) under various climate change scenarios are often used
by climate and sea level scientists to help communicate the physical
basis for societal concern regarding sea-level rise. Changes in ESLs
(i.e., the hazard) are often represented using various metrics and
indicators that, when anchored to salient impacts on human systems and
the natural environment, provide useful information to policy makers,
stakeholders, and the general public. While changes in hazards are often
anchored to impacts at local scales, aggregate global summary metrics
generally lack the context of local exposure and vulnerability that
facilitates translating hazards into impacts. Contextualizing changes in
hazards is also needed when communicating the timing of when projected
ESL frequencies cross critical thresholds, such as the year in which
ESLs higher than the design height benchmark of protective
infrastructure (e.g., the 100-yr water level) are expected to occur
within the lifetime of that infrastructure. We present specific examples
demonstrating the need for such contextualization using a simple flood
exposure model, local sea-level rise projections, and population
exposure estimates for 414 global cities. We suggest regional and global
climate assessment reports integrate global, regional, and local
perspectives on coastal risk to address hazard, vulnerability and
exposure simultaneously.