The most comprehensive assessment to date of Australia’s climate was jointly released October 4 by the Bureau of Meteorology and CSIRO.
Climate Change in Australia provides the latest information on observed climate change over Australia and its likely causes, as well as updated projections of changes in temperature, rainfall and other aspects of climate that can be expected over coming decades as a result of continued global emissions of greenhouse gases.
“By 2030 we expect temperatures will rise by about 1ºC over Australia compared with the climate of recent decades,” says one of the report’s authors, CSIRO’s Dr Penny Whetton. “The probability of warming exceeding 1°C is 10-20 per cent for coastal areas and more than 50 per cent for inland regions.”
The amount of warming later this century will depend on the rate of greenhouse gas emissions. “If emissions are low we anticipate warming of between 1ºC and 2.5ºC around 2070, with a best estimate of 1.8ºC,” Dr Whetton says. “Under a high-emission scenario the best estimate is 3.4ºC, with a range of 2.2ºC to 5ºC.
With high emissions, the chance of exceeding 4°C is around 10 per cent in most coastal areas and 20-50 per cent inland. There will also be changes in temperature extremes, with fewer frosts and substantially more days over 35ºC.”
“By 2030 we expect temperatures will rise by about 1ºC over Australia compared with the climate of recent decades,” says one of the report’s authors, CSIRO’s Dr Penny Whetton.
Increasing levels of greenhouse gases are likely to cause decreases in rainfall in the decades to come in southern areas during winter, in southern and eastern areas during spring, and in south-west Western Australia during autumn, compared with conditions over the past century.
As with temperature, rainfall projections for later in the century are more dependent on the level of greenhouse gas emissions. “Under the low-emission scenario in 2070, annual rainfall decreases in southern Australian range up to 20 per cent, and up to 30 per cent under the high-emission scenario,” Dr Whetton says. “An increase in the number of dry days is expected across the country. However, when it does rain, it is likely to be more intense,” she says.
The report also states that:
- droughts are likely to become more frequent, particularly in the south-west
- evaporation rates are likely to increase, particularly in the north and east
- high-fire-danger weather is likely to increase in the south-east
- sea levels will continue to rise
Another of the report’s authors, Dr Scott Power from the Bureau of Meteorology (BoM), says Australia’s average temperatures have increased since 1950, the surrounding oceans have warmed and sea levels have risen.
“The temperature increases are likely to be mostly due to increases in greenhouse gases from human activities,” Dr Power says. “Since 1950, most of eastern Australia and south-west Australia have also experienced substantial rainfall declines. Attributing causes to rainfall changes is more difficult but the increase in greenhouse gases is likely to have contributed to the drying in the south-west and is a major suspect in the east,” he says.
“We need to plan ahead, to reduce risks and make the most of any opportunities that may arise as a result of global warming,” Dr Power says. “The information in Climate Change in Australia is critical for that planning.”
The report was developed by CSIRO and the BoM, in partnership with the Australian Greenhouse Office, through the Australian Climate Change Science Program.
It was presented at Greenhouse 2007 in Sydney.
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