Limiting global warming to 1.5 degrees this century could halve sea-level rise caused by melting ice sheets and glaciers, scientists have found.
The analysis of vast amounts of data by supercomputer modelling found sea level rises from melting ice could be reduced to 13cm from the predicted 25cm by 2100, if current pledges under the Paris Agreement to cut carbon emissions are delivered – meaning rising temperatures are curbed to 1.5 degrees.
Halving sea level rises from land ice could help reduce a predicted increase in severe coastal flooding, according to Dr Tamsin Edwards of King's College London, who led the research.
A second study, however, indicates warming of 3 degrees could cause sea level to increase by 0.5 cm every year by 2100 as a result of melting Antarctic land ice, with accelerated loss from 2060.
The findings provide insight into the likely immense impact of melting land ice – mainly in the Antarctic and Greenland – on global sea-level rises caused by climate disruption. This accounts for 50 per cent of sea-level rise, while the other half comes from oceans expanding as they warm.
Both studies were published in Nature on Wednesday, and highlight that aggressive efforts to limit global warming will sharply reduce future sea-level rise. Since 1993, land ice has contributed to around half of all global sea-level rise.
The Antarctic Ice Sheet is the largest land ice reservoir and its ice loss is already accelerating. However, it is much less likely to become unstable and cause a dramatic sea-level rise in upcoming centuries if the world follows policies that keep global warming below the key Paris target of 1.5 degrees, the researchers conclude.
Dr Edwards said: “Global sea level will continue to rise, even if we halt all emissions now, but our research suggests we could limit the damage: if pledges were far more ambitious, central predictions for sea level rise from melting ice would be reduced from 25cm to 13cm in 2100, with a 95 per cent chance of being less than 28cm rather than the current upper end of 40cm.”
It would also reduce Greenland ice sheet losses by 70 per cent, but the researchers warned Antarctica was a "wild card", with uncertainty over the impact of rising temperatures on melting ice and increasing snowfall on the continent. There was a one in 20 chance of Antarctica contributing 56cm of sea level rise in 2100 even if warming was limited to 1.5 degrees.
At 2 degrees of warming, ice loss from the continent will continue at a similar rate to today throughout the 21st century, the second study by scientists in the US, Canada and China found.
But if the world carries on its current track towards 3 degrees of warming there will be an “abrupt jump” in the pace of Antarctic ice loss, with “the possibility that rapid and unstoppable sea-level rise from Antarctica will be triggered if Paris Agreement targets are exceeded”.
If the most extreme ice sheet behaviour is assumed, Antarctic ice loss could be five times higher, which would increase median sea-level rise to 42 cm under current pledges.