The ACCESS coupled model: documentation of core CMIP5 simulations and initial results

There are two versions of global coupled climate models developed at the Centre for Australian Weather and Climate Research (CAWCR) participating in phase 5 of the Coupled Model Inter-comparison Project (CMIP5), namely ACCESS1.0 and ACCESS1.3. This paper describes the CMIP5 experimental configuration of the ACCESS models and the climate forcings for the historical and future scenario runs. We also present an initial analysis of model results, concentrating on changes in surface air temperature and the hydrologic cycle, and on climate sensitivity. Both models somewhat underestimate the observed 20th century warming, particularly in mid century, though recent warming rates match those observed. Mean warming for 2081–2100 relative to 1986–2005 under the RCP8.5 scenario is 3.61 K and 3.56 K for ACCESS1.0 and ACCESS1.3 respectively, and under RCP4.5 it is 2.34 K and 2.12 K. Climate sensitivity from idealised simulations is 10–15 per cent larger in ACCESS1.0 than ACCESS1.3 and both models are above the median of the range of CMIP3 and published CMIP5 results.