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Zusammenfassung:
The land ice contribution to global mean sea level rise has not yet been predicted with
ice sheet and glacier models for the latest set of socio-economic scenarios, nor with
coordinated exploration of uncertainties arising from the various computer models
involved. Two recent international projects generated a large suite of projections using
100 multiple models, but mostly used previous generation scenarios and climate models, and
could not fully explore known uncertainties. Here we estimate probability distributions
for these projections under the new scenarios using statistical emulation of the ice sheet
and glacier models, and find that limiting global warming to 1.5°C since preindustrial
would halve the land ice contribution to sea level rise this century, relative to
105 predictions for current climate pledges under the Paris Agreement: the median
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decreases from 25 to 13 cm sea level equivalent (SLE) by 2100, with glaciers responsible
for half the sea level contribution. The Antarctic contribution does not show a clear
response to emissions scenario, due to competing processes of increasing ice loss and
snowfall accumulation in a warming climate. However, under risk-averse (pessimistic)
assumptions, Antarctic ice loss could be five times higher, increasing 110 the median land
ice contribution to 42 cm SLE under current policies and pledges, with the upper end
(95th percentile) exceeding half a metre even under 1.5°C warming. This would severely
limit the possibility of mitigating future coastal flooding. Until climate policies and the
Antarctic response are further constrained, adaptation must therefore plan for a factor
115 of three uncertainty in the land ice contribution to global mean sea level rise.
