Australia
October 2, 2007
The most comprehensive assessment
to date of Australia’s climate was jointly released today by the
Bureau of Meteorology and CSIRO
at GREENHOUSE 2007 in Sydney.
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.”
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.
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.
Climate Change in Australia will be an important resource for
government, business and community groups.
“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.”
Developed by CSIRO and the BoM, in partnership with the
Australian Greenhouse Office, through the Australian Climate
Change Science Program: 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; and, sea levels will
continue to rise.
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