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Climate Variability and Change (continued)

Climate change projections

To determine the effect of increasing concentrations of greenhouse gases, researchers use global climate models to project the future climate over Australia. Climate change projections are not predictions. Rather, they give information about possible changes in future climate.

Global climate models consist of hundreds of interrelated mathematical equations that are processed on supercomputers to simulate weather patterns of the globe. These models can project temperature and rainfall changes over Australia under conditions of increased greenhouse gases. For planning purposes and sensitivity studies to assess the effect of climate change, CSIRO (2001) has developed a range of possible future temperature and rainfall projections that take into account the uncertainties in projecting future climate. Figures 60 and 61 show projected temperature and rainfall changes based on global climate models.

In the projection for 2030, most of Australia warms by 0.4 to 2.0C, with slightly less warming in some coastal areas and Tasmania, and slightly more warming in the north-west of the country. Greatest warming occurs in spring and least in winter. In the north-west, most warming occurs in summer. For 2070, the warming is 1.1 to 6.0C with regional and seasonal variations similar to those for 2030.

In most locations, annual average rainfall could increase or decrease around 2030 and 2070, relative to 1990. Changes are biased toward decrease in the south-west (-20 to +5% by 2030 and -60 to +10% by 2070), and in parts of the south-east and Queensland (-10 to +5% by 2030 and -35% to +10% by 2070). Most other locations show changes which vary from -10 to +10% by 2030 and -35 to +35% by 2070. Decreases are most pronounced in winter and spring. Some inland and eastern coastal regions may become wetter in summer, some inland areas may become wetter in autumn.

Increases in evaporation are associated with an increase in temperature. In most locations, this is not offset by increasing rainfall, which implies drier conditions in future. This could increase moisture stress to humans, livestock and vegetation.

Implications

Measurement and monitoring of atmospheric greenhouse gas concentrations are of high quality, with Australia making an important contribution through observations taken at the Cape Grim Baseline Air Pollution Station and elsewhere. All measurements indicate strong increases in greenhouse gas concentrations in the 1900s at rates faster than typical over the previous 1000 years.

A range of measures have been implemented to cut back Australia's greenhouse gas emissions, which rose in 1990 to 1998. The new measures outlined in this Report will mean growth in emissions is more likely to be constrained in coming years. However, Australia's total greenhouse gas emissions are relatively small compared with those of other OECD countries, whose emissions are also predicted to rise, causing global greenhouse gas concentrations to continue to increase.

Global climate models suggest substantial changes in climate in Australia towards 2050. Increases in temperature, predominantly decreases in rainfall over most parts of Australia and increases in moisture stress are likely as a result of enhanced greenhouse conditions. These projections have implications for human and natural systems, and will need to be assessed in order to plan for climate change. Careful planning will minimise the harm caused to the environment and the economy, while maximising positive consequences of climate change.

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