Figure 8.18: Power spectra
of the detrended globally averaged annual mean surface air temperature (SAT) anomaly.
The curves represent the estimates obtained from HadCM2 (blue), GFDL_R15_a (green)
and ECHAM3/LSG (red). The observed (black line) is from the globally averaged
annual mean SAT anomalies compiled by Jones and Briffa (1992). The spectra are
smoothed Fourier transforms of the autocovariance function using a Tukey window
of 100 lags for the models and 30 lags for the observations. The two vertical
lines represent the range of 95% confidence in the spectral estimates for the
model and the observations. Taken from Stouffer et al. (2000).