Modelling Earth's future climate is a complex but critical task
To understand Earth's variable and changing climate, scientists rely on climate models. Since the global climate and Earth system is complex and dynamic, climate models are necessarily complex too.
Coupled earth system models are large computer codes that simulate the components of the climate system and how they interact - ocean, atmosphere, sea-ice, land surface, carbon cycle, atmospheric chemistry, and aerosols. Model simulations run for weeks on high-performance supercomputers operated by the National Computational Infrastructure (NCI).
Running these models for different future scenarios, such as low or high carbon emissions, allows scientists to simulate a range of potential future changes in the Earth's climate and carbon cycle.
Investing in Australia's own Earth system model
Together with the Bureau of Meteorology, Australian universities and international collaborators, we developed the Australian Community Climate and Earth System Simulator (ACCESS), a fully coupled earth system model that provides a national weather, climate and Earth system modelling capability for operations and research. At CSIRO, we use ACCESS to contribute to major international climate modelling and prediction projects.
Through the World Climate Research Programme's Coupled Model Intercomparison project (CMIP6), ACCESS is providing input to the sixth assessment report of the Intergovernmental Panel on Climate Change (IPCC) on the world's climate future.
Contributing to international climate change assessments is one way that the ACCESS model can support decision-making by governments, industry and the general community.
The ACCESS CMIP6 submission
CMIP6 is a coordinated set of climate model experiments that enables the evaluation and comparison of climate models from across the world. Experiments are designed to assess a model’s climate sensitivity as well as its ability to reproduce 20th century climate.
Other experiments allow modellers to simulate climate to 2100 for a range of future socioeconomic pathways. For example, we can compare cases where carbon dioxide in the atmosphere stabilises or continues to increase at different rates. This allows us to investigate how rapidly the planet warms in each case - and how this impacts the climate in different part of the world. Some models can also simulate the carbon cycle. This means we can explore how the land and ocean take up carbon as atmospheric carbon dioxide changes and warming occurs.
CSIRO is participating in CMIP6 using two ACCESS versions.
- ACCESS-CM2 has up-to-date atmosphere and sea-ice components and is targeted at physical climate simulations.
- ACCESS-ESM1.5 simulates the carbon cycle alongside climate.
The ACCESS simulations for each of these scenarios provide extensive datasets encompassing a wide range of variables that characterise the climate such as temperature, rainfall, cloud cover, sea-ice extent and ocean circulation. Datasets from ACCESS, as well as all other models participating in CMIP6 are freely available through the Earth System Grid Federation.
The ACCESS submissions to CMIP6 have been supported by the National Environmental Science Program Earth Systems and Climate Change Hub.