The Australian Community Climate and Earth System Simulator (ACCESS) is Australia's national weather forecasting and climate prediction system, providing world-class modelling infrastructure to the Bureau of Meteorology, CSIRO, two ARC Centres of Excellence and other University researchers around the country, as well as global collaborators. The role of NCI, as highlighted in the 2016 National Research Infrastructure Roadmap, is as a piece of critical infrastructure for delivering Australia's weather and climate prediction system to the whole research community, including innovative research addressing how the mean state and climate extremes affect us. The outcomes of improvements to ACCESS directly enhance the work of other sectors such as business, industry, government and environmental management.

ACCESS is a complex coupled-system model that comprises atmosphere, ocean, sea-ice, land and other components—derived from the best models of the UK, USA, France and Australia to provide our national weather and climate prediction capability. The model's complexity and design enables it to be used over a range of time scales: from hours for extreme weather events (storms and bushfires), through to days for general weather prediction, months and years for seasonal prediction, and centuries for long-term climate change modelling. The outcomes for Australia are wide-ranging and underpin services that provide multi-billion dollar benefits for agriculture and industry. These include improved weather prediction and more accurate seasonal prediction, improved risk management and public safety during extreme weather events, and the provision of essential tools and information systems for long-term policy and decision-making.

ACCESS is developed through a collaboration of the Bureau of Meteorology, CSIRO, the academic community through the ARC Centre of Excellence in Climate System Science and NCI.  NCI's role is essential, not only as the collaborative, integrated development platform but also through its unique expertise in optimising the performance of key model components. Performance improvements of 30-40% and much higher code scalability (up to 20-fold improvements, with some codes now exploiting up to 20,000 cores) enable greater operational efficiency and productivity for the Bureau and the broader research community. This leads to a faster time to results, more accurate simulations that enable new scientific outcomes and insight, and heightened prediction capability. These contributions are fed back into international systems through the UK Met Office and the National Oceanic and Atmospheric Administration in the USA, and are essential in such a world-class collaboration.