Although populations affected by the Australian monsoon are much smaller than those affected by the South and East Asian monsoons, regional impacts of changes in monsoon timing or strength are nevertheless likely to be large, particularly on vulnerable indigenous populations and sensitive ecosystems. The strength of the Australian summer monsoon is known to vary naturally on interannual and decadal time scales, with recent trends towards increased rainfall in the north-west attributed, at least partially, to anthropogenic aerosol forcing. We report on the simulation of interannual variability of Australian monsoon rainfall in CMIP5 models. We investigated changes in monsoon rainfall in future climate simulations under the high emission “RCP8.5” scenario. Projections of the Australian monsoon response to a warming climate in CMIP5 models show little change in mean summer rainfall over tropical northern Australia, consistent with results from CMIP3 models. The focus in this study is therefore on the changes in the rainfall variability and extremes associated with the Australian monsoon.