Curbing global warming to 1.5C would halve sea level rise from ice melt – study

Limiting global warming to 1.5C would halve the sea level rise the world will face this century from melting ice sheets and glaciers, a study has suggested.

The analysis found sea level rises from melting ice could be reduced from a central prediction of 25cm by 2100 if only current pledges to cut greenhouse gas emissions are delivered, to 13cm if rising temperatures are curbed to 1.5C (2.7F).

Halving sea level rises from land ice could help reduce the increase in severe coastal flooding, the scientists said.

Melting land ice, including the Greenland and Antarctica ice sheets and glaciers around the world, has contributed around half of all sea level rise since 1993, with the other half coming from the oceans expanding as they warm.

The share of sea level rise coming from land ice is expected to increase.

Under the Paris climate treaty, countries have committed to keep global temperature rises to “well below” 2C (3.6F) above pre-industrial levels and to pursue efforts to curb them to 1.5C to prevent the worst impacts on climate change.

But the world is well off track to meet the tougher 1.5C limit, as up until recently national plans for cutting climate-warming emissions added up to rises of more than 3C (5.4F) – although in the past few months countries have been bringing forward more ambitious pledges to tackle the crisis.

Dr Tamsin Edwards, from King’s College London, 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% chance of being less than 28cm rather than the current upper end of 40cm.

“This would mean a less severe increase in coastal flooding.”

The study, published in the journal Nature, used hundreds of computer models and statistical analysis to predict that limiting global warming to 1.5C would halve losses from glaciers, compared to the national plans in 2019 before countries brought forward new pledges.

It would also reduce Greenland ice sheet losses by 70% 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 1.5C.

Dr Edwards warned that coastal flood management must be flexible enough to account for a wide range of possible sea level rise, until observations and modelling could provide more clarity on Antarctica’s future.

A second paper, also published in Nature, suggests that warming of 3C could cause sea levels to increase by 0.5cm every year by 2100 from the melting of the Antarctic ice sheet.

At 2C of warming, ice loss from the continent will continue at a similar rate to today throughout the 21st century, the study from scientists in the US, Canada and China found.

But if the world carries on its current track towards 3C of warming there will be an “abrupt jump” in the pace of Antarctic ice loss, with the researchers warning of the “possibility that rapid and unstoppable sea-level rise from Antarctica will be triggered if Paris Agreement targets are exceeded”.