Abstract
Probabilistic sea level projections are frequently used to characterise the uncertainty in future sea level rise. Here, it is investigated how different modelling assumptions and process estimates affect such projections using two process-based models that add up the sea level contributions from different processes such as thermosteric expansion and ice sheet melt. A method is applied to estimate the direct contributions from the different processes as well as that of nonlinear interactions between the processes to the projections. In general, the nonlinear interaction terms are found to be small compared to the direct contributions from the processes, and only a few interaction terms give significant contributions to the projections. Apart from the process estimates, probabilistic models often also incorporate some expert judgements that inflate the uncertainty compared with that derived from climate and ice-sheet models, and the effects of some such judgements are also evaluated and found to have a considerable influence on the projections. Lastly, sea level projections are most often given contingent on representative concentration pathways for atmospheric greenhouse gases. Here, we generalize this approach by also providing projections for a probabilistic baseline scenario.
Highlights
Sea level rise is an ongoing and accelerating process that already affects many coastal communities around the world [1]
The interaction terms are more different between the two projections than the direct contributions, at least under RCP8.5
To get a sense of the uncertainties involved in this approximation, we present a complementary set of estimates that do not rely on a global mean surface temperature (GMST)-global mean sea level (GMSL) relationship, but that instead make assumptions about the likelihood of the representative concentration pathways (RCPs)
Summary
Sea level rise is an ongoing and accelerating process that already affects many coastal communities around the world [1]. Projecting how the sea level might change in the future is an important undertaking, and regularly updated projections are offered by among others the Intergovernmental Panel on Climate Change (IPCC). Such projections are most often contingent on representative concentration pathways (RCPs), where the concentrations of atmospheric greenhouse gases are prescribed. Process-based models are used to sum up contributions to sea level rise from different processes. If one looks at sea level regionally, ocean dynamics, glacial isostatic adjustments and several other processes may give important contributions
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