Grönland: So warm wie seit 1000 Jahren nicht

Greenland: Warmer than it has been for 1000 years - In 2012, temperatures above freezing were measured for the first time in the centre of the Greenland ice sheet. The associated surface melting, particularly in the lower marginal areas, influences the mass balance of the ice sheet and contributes to global sea level rise. In order to understand whether these episodes of increased temperature represent single extreme events of strong climate variability or whether they are signatures of global warming that will occur more frequently in the future, the observations of recent years must be placed in a historical context. What is the natural variability of temperature in central Greenland? How often have comparable warm episodes occurred in the past? Are these events isolated extreme cases or are they the result of a longer-term warming trend? This chapter reports on a new temperature reconstruction of the last 1000 years from Greenland ice cores and shows that the exceptionally high temperatures of the decade from 2001 to 2011 resulted from a superposition of natural variability and a long-term warming trend that has been visible since 1800 AD. This disproportionate warming in the north and centre of Greenland is accompanied by an increased outflow of meltwater in the peripheral areas of the ice sheet. The data show that anthropogenic global warming has also reached the remote area of northern and central Greenland and is now affecting the entire ice sheet, which could further accelerate global sea-level rise through the Greenland ice sheet.