Media release

From: Springer Nature

Assessing the future stability of the Greenland ice sheet

The Greenland ice sheet is projected to undergo abrupt losses due to melting if global warming exceeds temperatures of around 2 °C above pre-industrial temperatures, according to a modelling study published in Nature. Subsequent cooling to below 1.5 °C may mitigate ice loss, but only if the cooling takes place within several centuries.

The Greenland ice sheet is estimated to have contributed more than 20% to the observed sea-level rise since 2002 as a result of melting due to rising temperatures. However, it is unclear how the ice sheet will respond to future temperature increases. Modelling and paleoclimate evidence, for example, have suggested that the ice sheet may stabilize at multiple different configurations along warming or cooling trajectories.

Nils Bochow and colleagues modelled the behaviour of the Greenland ice sheet under future warming scenarios in which temperatures first exceed critical thresholds for ice-sheet stability, followed by a reduction in the global mean temperature. The authors suggest that the stability of the ice sheet is influenced by both the length of time for which temperatures are exceeded and the extent by which they are elevated. They found that abrupt ice-sheet loss is likely if the global mean temperature threshold is between 1.7 °C and 2.3 °C above pre-industrial levels. The analyses indicate that this loss can be mitigated — even for maximum warming of up to 6 °C or more above pre-industrial levels — if global mean temperatures are subsequently reduced to 1.5 °C within a few centuries. Timing, though, is crucial: if the return to cooler temperatures after an ‘overshoot’ of the threshold takes more than a few centuries, then the ice sheet is still likely to contribute several metres to sea-level rise.