CO2-induced climate change in northern Europé: comparison of 12 CMIP2 experiments.

The results of 12 coupled atmosphere-ocean general circulation model experiments participating in the second phase of the Coupled Model Intercomparison Project (CMIP2) are studied with focus on the area of northern Europe. The variables considered are surface air temperature, precipitation and sea level pressure. The 80-year control simulations are first compared with observational estimates of the present climate. Several aspects of the simulated CO2-induced climate changes, defined by subtracting the control run seasonal or annual means from 20-year perturbation run means around the transient doubling of CO2, are then studied. The common features and individual variations in the simulated climate change are documented. Particular attention is put on expressing the interexperiment agreement in quantitative terms and on estimating the relative contribution of model- simulated internal variability to the interexperiment variance. For that purpose, a new statistical framework is developed. Finally, an attempt is made to statistically relate the interexperiment differences in the simulated climate change in northern Europe to aspects of the control climates, global climate change and some of the basic model characteristics. A summary of the main findings is given in the last section of the report