Global power law scaling of near surface temperature spectra is determined in two scenario simulations and in NCEP re-analyses. The simulations use the coupled atmosphere-ocean models HadCM3 and ECHAM4/OPYC with greenhouse gas increase according to scenario IS92a in 1860--2099. Observations show a low-frequency power spectrum S(f) ~ 1/f over the oceans, a white spectrum in the inner continents, and S(f) ~ f-0.3 in the coastal areas. The global distribution of the power law exponents is reproduced in the two simulations even in the 21st century with a pronounced temperature increase.