| Summary: | Uncertainty in future carbon dioxide (CO2) emissions, and the geophysical response to emissions, drives variability in future sea-level rise (SLR). However, the relative contribution of emissions and geophysical dynamics (e.g. Antarctic Ice Sheet (AIS) tipping points) to future sea-level projections is poorly understood. Here, we disentangle their relative importance by propagating several ensembles of CO2 emissions trajectories, representing relevant deep uncertainties, through a calibrated carbon cycle-climate-sea-level model chain. The CO2 emissions trajectory, particularly the timing of when emissions are reduced, becomes the primary driver of sea-level variability only after 2075. The most extreme global mean SLR (exceeding 4m by 2200) is projected to occur regardless of optimism about limiting CO2 emissions if accelerated AIS melting occurs. Further, delaying decarbonization reduces the “safe operating space” associated with the geophysical uncertainties. Our results highlight the potential that similar adaptation requirements may be needed regardless of optimism about future levels of CO2 mitigation.
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