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The challenge

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.

Our response

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 results

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.

[Image appears of two globes with continental outlines and coloured shading. The coloured shading represents the change in temperature at each point on the globe relative to the average temperature for 1850 to 1900. The pattern of temperature change is shown for each year from 1950 to 2100. The year is indicated at the bottom left of each globe.]

[The two globes show the same temperature changes until 2014. These results are from the CMIP6 historical simulation. In 2014 the globe shows there are very small regions with below zero temperature change. Most of the globe shows temperature changes of 0 to 1 degrees C. Some land regions show temperature changes of 1 to 2 degrees C and in the high northern latitudes there are regions of 2 to 3 degrees C with a small area up to 5 degrees C]

[From 2015 the two globes show different results. The temperature changes are from two model simulations representing scenarios with low and high carbon emissions. The temperature changes shown on both globes are similar until the 2040s. In 2040 most of the globe shows a temperature change of at least 1 degrees C, with most land regions greater than 2 degrees C. As the simulations continue the two cases diverge. At 2100 the low emissions case is only a little warmer than in 2040. The high emissions case shows temperature changes of 3-5 degrees C over the ocean and greater than 6 degrees C over land.]

[Global mean delta T (temperature change) is given on the bottom right of each globe, changing with each year of the simulation. Numbers for selected years are given here for the low emissions case first and then the high emissions case].

[1950, 0.0, 0.0]

[1980, 0.1, 0.1]

[2010, 0.8, 0.8]

[2020, 1.2, 1.3]

[2030, 1.7, 1.6]

[2040, 2.0, 2.1]

[2050, 2.1, 2.7]

[2060, 2.3, 3.3]

[2070, 2.4, 4.0]

[2080, 2.4, 4.7]

[2090, 2.7, 5.4]

[2100, 2.5, 6.2]

Data visualisation: R. Bodman, University of Melbourne/CSIRO

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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.

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