Many climate models have dry biases in the tropical monsoon regions, but it is less clear how these errors have affected the model-simulated tropical-extratropical interactions and rainfall teleconnections. In this study, we evaluate the Australia and Asian (A-A) monsoon rainfall in three versions (Global Atmosphere component GA 6, GA7 and prototype GA8) of the UK Met Office Unified Model (UM) with AMIP-type simulations. UM is known to have climatological rainfall dry bias over the Indian subcontinent, but this dry bias is progressively reduced by increased model resolutions and improved model physics from GA6 to GA7. Although GA7N216 still suffers a dry bias in the Indian monsoon region, the increased monsoon rainfall almost doubled the atmospheric diabatic heating in the middle-upper troposphere, leading to more realistic extratropical circulation Gill-type responses to the monsoon-induced diabatic heating. This results in improved monsoon-desert rainfall teleconnections, more realistic linkage between the tropical Asian monsoon with its subtropical East Asian component, and its interhemispheric influence in the Southern Hemisphere. Some results from UM prototype GA8 runs will also be presented. Our study clearly demonstrates that uncertainty associated with model monsoon simulations needs to be considered in future climate projections even outside the monsoon domain.