In response to increasing carbon dioxide emissions the oceans have become warmer and more acidic. In this paper, the ability of Earth System Models to simulate observed temperature and ocean acidification around Australia is as-sessed. The model results are also compared with observations collected at sta-tions around Australia over recent years to assess how representative the model results are of the coastal domain; and are found to adequately simulate the mean state at most sites. Simulations from the Coupled Model Intercomparison Project 5 (CMIP5) under low, medium and high emissions scenarios (RCPs 2.6, 4.5 and 8.5 respectively) are then used to project how ocean acidification and sea surface temperature will change. Under each of these emissions scenarios the oceans around Austral-ia exhibit warming and continued acidification. However, these changes are quite heterogeneous, with increases of up to +6 K (under RCP 8.5) above the pre-industrial value, projected in areas such as the Tasman Sea. We conclude that the projected changes in SST, aragonite saturation state and pH are likely to profoundly impact marine ecosystems, and the ecosystem services that they provide in the Australasian region.
