Climate models are based on the laws of physics and are run on supercomputers.
They use mathematical representations to simulate the complex interactions of the Earth's climate system, including atmospheric, oceanic, hydrological and terrestrial processes and atmospheric chemistry.
The models are validated by simulating climate in previous decades and then comparing the results of the model with recorded measurements of temperature, rainfall and other climatic variables.
There are over 40 climate models developed by groups from around the world. Some simulate the past climate better than others, especially at the sub-continental scale, so it is important to derive regional projections from models that perform well.
ACCESS: Australia's climate model
One such model is ACCESS, the Australian Community Climate and Earth System Simulator. ACCESS produces the Bureau of Meteorology's Australian weather forecasts, which you see on the evening news.
This is one of the models that CSIRO researchers are using to project climate in the coming century, building on more than 20 years of research into developing climate projections for Australia.