Scaling of Atmosphere and Ocean Temperature Correlations in Observations and Climate Models

Power-law scaling of near surface air temperature fluctuations and its geographical distribution is analyzed in 100-yr observations and in a 1000-yr simulation of the present-day climate with a complex atmosphere-ocean model. In observations and simulation detrended fluctuation analysis leads to the scaling exponent $\alpha \approx 1$ over the oceans, $\alpha \approx 0.5$ over the inner continents, and $\alpha \approx 0.65$ in transition regions [spectrum $S(f)\sim f^{-\beta },\beta =2\alpha -1$]. Scaling up to decades is demonstrated in observations and coupled atmosphere-ocean models with complex and mixed-layer oceans. Only with the complex ocean model the simulated power laws extend up to centuries.