  Using detrended fluctuation analysis (DFA), we study the scaling properties
of the volatility time series $V_i=| T_{i+1}-T_i|$ of daily temperatures $T_i$
for ten chosen sites around the globe. We find that the volatility is long
range power-law correlated with an e xponent $\gamma$ close to 0.8 for all
sites considered here. We use this result to test the scaling performance of
several state-of-the art global climate models and find that the models do not
reproduce the observed scaling behavior.
