Australia has always experienced natural climate variability such as heatwaves, floods and drought. But with global concentrations of carbon dioxide (CO2) and other greenhouse gases rising to the highest concentrations in at least two million years, multiple lines of evidence indicate that this will warm the climate and enhance many types of extreme events.
Providing reliable future insights to help Australia build resilience and respond to change is a challenge our climate modelling science is helping to address.
How climate modelling works
Climate modelling uses the well-understood laws of physics that describe the behaviour of weather systems and ocean currents. It then brings in scientific understanding of other aspects of the climate system such as the land surface, ice and chemistry to integrate and simulate the whole system.
“We use extensive data on the historical changes in greenhouse gases, aerosols, solar cycles and other factors that drive changes in climate, referred to as ‘forcings’. Models can then be used to assess how the Earth system responds to these forcings, and how it would respond to further changes,” says Mr John Clarke from CSIRO’s Regional Projections Team.
Climate modelling across the globe
In Australia, the weather and climate are strongly influenced by features such as the influence of El Niño, La Niña and the variability of the Indian Ocean Dipole. Whereas the climate of a country in Europe, for example, has a different set of influences such as processes in the north Atlantic. This means that climate modelling needs to look specifically at the climate of the region.
“The international research community has produced a standardised set of plausible scenarios of future development and greenhouse gas changes. These are referred to as Representative Concentration Pathways – or RCPs – as used by the Intergovernmental Panel on Climate Change,” explains Clarke.
"Climate model simulations are then run under these RCPs to see how the climate responds and what impacts each scenario brings. They are also influenced largely by what humans do, so it’s a difficult task. But our science allows us to narrow the range of futures to what’s scientifically plausible.”
Climate modelling can be applied on a global, national, regional and local scale.
Historical snapshot of climate forecasting
The first attempts to understand the effect of increasing greenhouse gases can be traced back to the 1800s, with scientists recognising the properties of CO2, and its role in affecting the planet’s temperature. The results back then proposed that if the amount of CO2 in the air would double then the temperature on the ground would increase by approximately 5 degrees Celsius – an estimate that is still plausible today.
Move forward 100 years and the ‘enhanced greenhouse effect’ started gaining international attention. In the 1980s, the United Nations formed the IPCC and CSIRO began its leading research on climate change and climate forecasting.
Over time there was a clear need for more data collection, greater understanding of the processes and feedbacks involved in climate change, and methods to integrate scientific knowledge and understanding. Climate models became invaluable tools in understanding and projecting climate change.
What past projections have revealed
National climate projections statements have been produced and released since the late 1980s, increasing in sophistication and scope through the years. A report generated by CSIRO in 1988 - Australian bushfire danger under changing climatic regimes – used climate modelling to highlight that Australia could face extreme risk from bushfire in the coming decades. The latest State of the Climate Report produced with the Bureau of Meteorology outlines that there has been a long term increase in extreme fire weather, and in the length of the fire season, across large parts of Australia.
“Our current modelling demonstrates that we’re on track with our projections for Australia. In 2019, Australia had its driest and hottest year on record. We’re set to become hotter and drier, with fire seasons lasting longer. What we do in response and how we build climate resilience is a big challenge,” states Research Scientist Dr Michael Grose.
Long-term data, long-term gains
“Our climate modelling highlights what we can expect in the future, but the results need to be carefully assessed and brought together with other lines of evidence to be used in decision-making,” explains Grose.
“It is important to understand the difference between climate and weather, and to understand the difference between climate variability and climate change. Unlike forecasts such as whether it’s going to rain on the weekend, climate change modelling operates on long-term scales. Climate projections are about the changing statistics of weather events over decades, rather than predicting any one event.”
The overall bushfire risk for each major fire event depends on the particular fuel type, dryness, weather and ignition sources. Climate change is affecting the bushfire weather, fuel and possibly the ignitions (via changes to lightning strikes). This is the context for decision-making on the factors that can be controlled such as management of fuels, preventing fire ignitions and management of fires once they start.
Evaluating modelling capabilities
The reliability of climate projections continues to increase. There’s more comprehensive data available than decades ago, greater understanding of the underlying processes, and ongoing model development by top researchers.
Evaluations of model performance are a routine part of model releases. Climate Change in Australia has the latest national climate projections information, and has tools to explore projections, understand the science behind them and obtain datasets.
“Climate projections of the change in global temperature made between 1970 and 2007 have been shown to be skilful. The biggest source of uncertainty has in fact been the prediction of human emissions,” says Clarke.
Through the Australian Community Climate and Earth System Simulator (ACCESS), CSIRO continues to build on past projections by developing Australia's next generation climate model. The models are key inputs to the global IPCC assessment reports.
“By contributing research, observations and modelling to the global research community, we are playing a key role in the scientific mission to understand climate change and project the future of our climate,” adds Clarke.
“With more data records available, modelling will only get better to help us manage future risk.”
Learn more about our climate and earth systems research.