Sustained input to the atmosphere of greenhouse gases will lead to long term warming with major consequences for the Greenland ice sheet. Gregory et al. (2004) calculate that a mere 2.7°C rise in Greenland mean temperature will cause the ice sheet to lose mass faster than it gains mass. For a 3°C warming Greenland would shrink to a smaller island, and an 8°C warming would cause the entire ice mass to disappear over about 1,000 years with a consequential rise of 7 meters in mean global sea level.
Reference
Gregory, J.M., P. Huybrechts, and S.C.B. Raper, 2004: Threatened loss of the Greenland ice sheet. Nature, 428, 616.