The cause of warming over Norway in the ECHAM4/OPYC3 GHG integration

The cause of warming over Norway in a future global climate model (GCM) scenario is examined. Analysis of historical observations indicate that the observed long-term temperature trends are not a result of systematic shifts in the North Atlantic Oscillation (NAO). The GCM prediction of past and future warming cannot be explained in terms of changes to the large-scale atmospheric flow. The climate model results may suggest that the model has a seasonal bias with respect to the time of the year when the fastest warming occurs. The NAO is associated with the warming after 1970, even though the 1860-1997 temperature trends do not appear to be connected with the NAG. An accurate description of the NAO is, therefore, critical for forecasting short-term Variability in the Norwegian winter climate and the results obtained here suggest that the model description of the NAO is generally good. Copyright (C) 2001 Royal Meteorological Society.