Approximately a third of the ice shelves restraining enormous glaciers in Antarctica are at risk of collapse if the world fails to take sufficient action on climate change, new projections suggest.

Floating portions of ice shelves are some of the most important ice on the planet. They act by holding back the flow of land ice into the ocean, effectively stabilizing glaciers coming down from the ice sheet that covers the continent.

The ice shelves circling the continent are vulnerable to meltwater on their surface causing the ice to crack and disintegrate, in a process known as hydrofracturing.

Computer modelling by Ella Gilbert at the University of Reading, UK, and Christoph Kittel at the University of Liege, Belgium, suggests that if the world warms by 4°C since pre-industrial levels, then 34 per cent of the continent’s ice shelves will have meltwater on their surface, a sign they are at risk of collapse.

However, the figure falls to 18 per cent if temperature rises are checked at 2°C. According to the respected Climate Action Tracker, the world is currently on track for a 2.9°C rise but, if implemented, climate plans and net zero goals would cut that to 2.1°C.

“Warming to 2°C means half the ice shelf area is at risk of collapsing. That is the message: the less the warming the better,” said Gilbert.

The latest research used a much higher resolution climate model than previous research, with grid squares 35 kilometres across rather than hundreds of kilometres across.

It also more accurately represents cloud physics, which is vital as estimates of the area at risk of collapse hinge on how much ice loss is replaced by snowfall. The main difference between the 2°C and 4°C rise scenarios stems from melting outweighing increased snowfall in a 4°C warmer world.

The Larsen C ice shelf on the east of the Antarctic Peninsula, where a huge iceberg broke off in 2017, was found to be one of the areas most at risk.

The research doesn’t put a figure on how much sea level rise could occur if ice shelves collapsed and released the glaciers behind them.