PNNL

Abstract

The current uncertainty surrounding the Earth’s equilibrium climate sensitivity is an important 23 driver for climate hazard projections. While the implications for projected global temperature 24 changes have been extensively studied, the impacts on sea-level projections have been 25 relatively unexplored. Here we analyze the relationship between the climate sensitivity and sea26 level projections, with a particular focus on the high-impact upper bound. We utilize a Bayesian 27 calibration of key climate and sea-level parameters using historical observations and the 28 reduced complexity Earth system model, Hector-BRICK. This methodology allows us to focus 29 on plausible realizations of the climate system in a probabilistic framework. We analyze the 30 effects of high-end climate sensitivity (above 5 K) on projections and spatial patterns of sea31 level change. The sea-level projections hinge critically on the upper tail of the climate sensitivity, 32 especially for the highly decision-relevant upper bound. Results have important implications for 33 timing of threshold exceedances and regional variability.