Is the Greenland Ice Sheet in a state of collapse?

The Greenland Ice Sheet is thinning at an accelerating pace and the ice sheet's contribution to sea‐level rise has doubled in less than a decade. New data show rapid and widespread changes in the behaviour of the ice sheet, particularly along the coastal margin. These changes coincide with a decade of sustained Arctic warming of up to 3 °C. Decay of the Greenland Ice Sheet in response to global warming will not only be governed by increased surface melting during longer and warmer summers but also by a speed‐up of coastal glaciers that drain the interior ice sheet. A precise estimate of sea‐level rise in the twenty‐first century relies on improved theoretical treatment of these glaciers in computer models.