Tropical tropopause layer (TTL) plays an important role in governing the large-scale distribution of moisture in the stratosphere, because air entering the stratosphere is strongly freeze-dried in the TTL.However, huge temperature variance in the TTL is found in both present and future climate simulations by multimodels of both Coupled Model Intercomparison Project phase 3 (CMIP3) and CMIP5.In this study, present reproducibility, future changes and uncertainties in the temperature and thermodynamic structure in the TTL are investigated.Uncertainties are evaluated using an atmospheric general circulation model (AGCM) with different cumulus convection schemes and sea surface temperature (SST) distributions.