Journal Article

Learning About Sea Level Rise Uncertainty Improves Coastal Adaptation Decisions

Hinkel, Jochen, MacPherson, Leigh R., Völz, Vanessa, Wulff Norrby, Carl Jacob, Kupfer, Sunna

2024

Overview

Adaptive decision‐making allows decision‐makers to plan long‐term coastal infrastructure under uncertain sea level rise projections. To date, economic assessments of adaptive decision‐making that take into account future learning about sea level rise uncertainty are rare and the existing ones have relied on simple quantification of future learning not validated against sea level science. To address this gap, we develop an economic adaptive decision‐making framework that takes into account future learning about sea level rise uncertainty and apply it to a coastal case study in Lübeck, Germany, to answer the question of how adaptation to sea level rise can be improved through adaptive adaptation pathways as opposed to non‐adaptive pathways. To address this question, we use a Markov decision process to formulate the stochastic optimization problem. We quantify future learning about sea level rise uncertainty through sea level rise learning scenarios based on and validated against the latest scenarios of the Intergovernmental Panel on Climate Change. Our case study results show that the city of Lübeck is currently under‐protected against storm surges and that immediate adaptation actions are advisable in the face of future sea level rise. We find that adaptive adaptation pathways, in contrast to non‐adaptive pathways, generate sea level rise thresholds for adaptation actions that are similar across climate change scenarios and can reduce expected costs up to 1.8%. Plain Language Summary Climate change is causing sea levels to rise as land ice melts under higher air temperatures. By 2100, sea levels are projected to rise between 28 and 101 cm, depending on the extent of future global warming. This will increase the risk of coastal flooding in the future and require adaptation actions. Planning for coastal adaptation to sea level rise is challenged by long‐lived protective infrastructure and uncertain projections of sea level rise. Adaptive decision‐making methods that specifically incorporate future learning about the uncertainty of sea level rise can address this challenge. For example, observing 30 cm of sea level rise in 2060 will lead to different projections from 2050 onwards and require different adaptation actions than observing 70 cm of sea level rise in 2060. To date, economic adaptation studies that account for future learning about sea level rise uncertainty are rare, and those that do exist have relied on simple methods. We develop a decision framework to address this research gap and apply it to the city of Lübeck on the Baltic Sea in Germany. Our results show that the city of Lübeck is currently under‐protected against storm surges and that immediate adaptation actions are advisable from an economic perspective. Key Points We develop adaptive adaptation pathways that incorporate learning about sea level rise uncertainty based on future observations Adaptive adaptation pathways generate sea level rise thresholds for adaptation actions that can be similar across climate change scenarios Adaptive adaptation pathways can reduce expected costs compared to non‐adaptive pathways by up to 1.8% in our study

• Publisher: John Wiley & Sons, Inc,American Geophysical Union,Wiley
• Subject: Adaptation / Case studies / Climate change / Climate change scenarios / climate uncertainty / Coastal zone management / Comparative analysis / Costs / Decision making / Discount rates / dynamic planning / Dynamic programming / Economics / Environmental aspects / Environmental Sciences / Intergovernmental Panel on Climate Change / Learning / learning scenarios / Markov analysis / Markov processes / Measurement / real‐option analysis / Risk assessment / Sea level / Sea level rise / Stochastic processes / Storm surges / Uncertainty