Australia
October 4, 2007
Southern Australia will continue
to experience a reduction in rainfall in winter and spring, the
impact of which will be magnified by increased temperatures.
Speaking at Greenhouse 2007, CSIRO’s
Dr Wenju Cai said the latest modelling by the Intergovernmental
Panel on Climate Change (IPCC) showed a 5 to 15 per cent
rainfall decrease by 2070.
“There is no longer any doubt that climate change caused by
increases in greenhouse gases is influencing seasonal shifts in
rainfall patterns,” Dr Cai said.
“Our results provide strong evidence that rising temperatures,
hence increasing evaporation due to the enhanced greenhouse
effect, impact on Australia’s water resources, in addition to
any reduction in rainfall.”
What could partially offset this is an increase in summer
rainfall in south east Australia, as simulated by some IPCC
models. This increase is consistent with a large Tasman Sea
warming where the ocean warming rate is the fastest in the
Southern Hemisphere.
Dr Cai said climate models also indicate that about half of the
rainfall decline in south west Western Australia can be directly
linked to increases in atmospheric greenhouse gas levels. He
said there are also likely to be further declines in rainfall in
north west Western Australia in the future.
He said rainfall shifts and seasonal variability in the
Australian region had three engines:
- the El Niño-Southern
Oscillation phenomenon in the Pacific Ocean
- a similar feature in the
Indian Ocean known as the Indian Ocean Dipole
- the Southern Annular Mode,
a pattern in the Southern Ocean that promotes air flows
towards south east Australia.
“I see two important challenges
for Australian scientists in this research field, the first
being the realistic simulation of the drivers linking ocean and
atmospheric conditions and seasonal rainfall,” Dr Cai said.
“The second is the development of more powerful models that will
narrow the uncertainties of climate modelling and develop more
specific projections for separate regions and centres within
Australia.”
Dr Cai is a lead author and co-author on several recent papers
examining the links between a changing climate and rainfall. His
work is supported by the Australian Greenhouse Office, the
Indian Ocean Climate Initiative, South East Australia Climate
Initiative and two CSIRO national research flagship programs –
Wealth from Oceans and Water for a Healthy Country.
His latest paper An interpretation of future projections of
Australian summer and winter rainfall co-authored with G. Shi,
J. Ribbe and T. Cowan has been accepted for publication in the
science journal, Geophysical Research Letters.
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