Global climate models violate scaling of the observed atmospheric   variability
  We test the scaling performance of seven leading global climate models by using detrended fluctuation analysis. We analyse temperature records of six representative sites around the globe simulated by the models, for two different scenarios: (i) with greenhouse gas forcing only and (ii) with greenhouse gas plus aerosol forcing. We find that the simulated records for both scenarios fail to reproduce the universal scaling behavior of the observed records, and display wide performance differences. The deviations from the scaling behavior are more pronounced in the first scenario, where also the trends are clearly overestimated. 
R.B.Govindan, Dmitry Vyushin, Armin Bunde, Stephen Brenner, Shlomo   Havlin and Hans-Joachim Schellnhuber