Simulation of secular trends in the middle atmosphere, 1950–2003

We have used the Whole Atmosphere Community Climate Model to produce a small (three‐member) ensemble of simulations of the period 1950–2003. Comparison of model results against available observations shows that for the most part, the model is able to reproduce well the observed trends in zonal mean temperature and ozone, both as regards their magnitude and their distribution in latitude and altitude. Calculated trends in water vapor, on the other hand, are not at all consistent with observations from either the HALOE satellite instrument or the Boulder, Colorado, hygrosonde data set. We show that such lack of agreement is actually to be expected because water vapor has various sources of low‐frequency…