• water vapor feedback;
  • seasonal cycle;
  • climate sensitivity

[1] We have analyzed the seasonal variations of global mean surface air temperature (SAT) and surface energy budgets of 17 AR4 models. Considerable differences in the amplitude of seasonal cycle (A) in the global mean SAT in the pre-industrial control simulations among the models have been traced, to a large degree, to differences in their simulated clear-sky downward longwave radiation (LW[DOWNWARDS ARROW]) and latent heat flux (LH). We suggest that water vapor feedback process influence the seasonal changes of SAT through its roles on the seasonal variations of LW[DOWNWARDS ARROW] and LH. This implies that the simulated seasonal change of global mean SAT might contain a clue about the sensitivity of water vapor feedback and the A of in SAT thus provides some constraint on climate sensitivity since both are subject to the same feedback process.