Global warming due to loss of large ice masses and Arctic summer sea ice

Several large-scale cryosphere elements such as the Arctic summer sea ice, mountain glaciers, and the Greenland and West Antarctic Ice Sheets have changed substantially during the last century due to anthropogenic global warming. However, the impacts of their possible future disintegration on global mean temperature (GMT) and climate feedbacks have not yet been comprehensively evaluated. Using an Earth system model of intermediate complexity, we quantify this response and find a median additional global warming of 0.43 °C (interquartile range: 0.39–0.46 °C) at a CO2 concentration of 400 ppm. Most of this response (55%) is caused by albedo changes, with lapse rate together with water vapour (30%) and cloud feedbacks (15%) also contributing significantly. While a decay of the ice sheets would occur on centennial to millennial time scales, the Arctic might become ice-free during summer within the 21st century. These findings imply an additional increase of GMT on intermediate to long time scales.