The Role of Climate Sensitivity in Upper-Tail Sea Level Rise Projections

The current uncertainty surrounding the Earth's equilibrium climate sensitivity is an important driver for climate hazard projections. While the implications for projected global temperature changes have been extensively studied, the impacts on sea level projections have been relatively unexplored. Here we analyze the relationship between the climate sensitivity and sea level projections, with a particular focus on the high-impact upper tail. We utilize a Bayesian calibration of key climate and sea level parameters using historical observations and the reduced-complexity Earth system model, Hector-BRICK. This methodology allows us to focus on plausible realizations of the climate system in a probabilistic framework. We analyze the effects of high-end climate sensitivity (above 5 K) on projections and spatial patterns of sea level change. The sea level projections hinge critically on the upper tail of the climate sensitivity, especially for the highly decision-relevant upper tail. Results have important implications for timing of threshold exceedances and regional variability.