Sea Level and Socioeconomic Uncertainty Drives High-End Coastal Adaptation Costs

Area of Science:

• Climate science
• Environmental modeling
• Risk assessment

Background:

• Coastal zones face significant risks from sea-level rise and flooding.
• Coastal adaptation models are crucial for managing these risks.
• Accurately representing deep uncertainties in these models is challenging.

Purpose of the Study:

• To assess how simplified uncertainty characterizations impact coastal impact projections.
• To compare benchmark percentile approaches with full ensemble analyses for sea-level rise uncertainty.
• To quantify the underestimation of risks and adaptation costs due to simplified uncertainty.

Main Methods:

• Utilized global mean sea-level rise data and socioeconomic parametric uncertainties.
• Employed benchmark cases (low, moderate, high percentiles) versus full ensembles.
• Analyzed projected coastal damages and adaptation costs under different Shared Socioeconomic Pathways (SSPs).

Main Results:

• Using few sea-level percentiles underestimates high-end damages (18-46%) compared to full ensembles.
• Benchmark percentiles underestimate the range of adaptation costs by a factor of two to four.
• Simplified uncertainty characterization leads to overconfident risk projections.

Conclusions:

• Simplified sea-level rise uncertainty characterizations result in underestimation of coastal risks.
• This underestimation can bias adaptation and mitigation decision-making.
• Full ensembles are necessary for robust coastal risk and adaptation assessments.