New research: contribution of land ice to 21st century sea level rise 6 May 2021

Australian Antarctic Division

Limiting global warming to 1.5°C could halve the contribution to sea level rise from melting land ice in Greenland and the world’s glaciers this century, a major study has found.

The finding by an international team of more than 80 scientists, led by Kings College London and involving Australian Antarctic Division glaciologist Dr Ben Galton-Fenzi, is published in Nature today.

The team used updated socio-economic scenarios in a new generation of climate models, to inform the Intergovernmental Panel on Climate Change’s Sixth Assessment report, which will be published later this year.

They found that if global warming was limited to 1.5°C – the goal of the Paris Agreement – Greenland ice sheet losses would reduce by 70% and glacier losses by half, compared with current emissions pledges.

However, Antarctica’s contribution to future sea level rise remains difficult to predict.

“It is currently unclear whether snow falling in the cold interior of the Antarctic ice sheet will offset melting at the coasts,” Dr Galton-Fenzi said.

“When we’re trying to model the future, Antarctica is the ‘wildcard’ of sea level rise – difficult to predict, yet critical for the upper end of projections.

“We found that in a worst-case scenario, where Antarctica is very sensitive to climate change, there is a five percent chance of the land ice contribution to sea level rise exceeding 56 cm in 2100 even if we limit warming to 1.5°C.”

The research team said predictions for sea level rise from melting ice around the world would be reduced from 25 cm to 13 cm in 2100 if pledges were more ambitious, and would see a less severe increase in coastal flooding.

Given the current uncertainty about Antarctica’s response to climate change, however, the research suggests coastal flood management must be flexible enough to account for a wide range of possible sea level rise.

“We need to be prepared for a range of impacts as we clarify Antarctica’s future with new observations and modelling,” Dr Galton-Fenzi said.

Dr Galton-Fenzi and colleague Chen Zhao were supported through the Australian Antarctic Program Partnership and Antarctic Gateway Partnership, and contributed to this work alongside Finnish collaborators Rupert Gladstone and Thomas Zwinger.

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