December
12, 2006
'ASIAN HAZE' IMPACTS ON AUSTRALIAN
RAINFALL
“Until now, there
has been ample evidence that these particles have important effects on
climate
in the Northern Hemisphere but little such evidence in the Southern
Hemisphere,” says CSIRO Marine and Atmospheric Research
scientist, Dr. Leon
Rotstayn.
“What
we have seen in our latest climate simulations is
that the ‘Asian haze’ is having an effect on the
Australian hydrological cycle
and generated increasing rainfall and cloudiness since 1950, especially
over
northwest and central Australia.
The effect occurs because the haze cools the Asian continent and nearby
oceans,
and thereby alters the delicate balance of temperature and winds
between Asia
and Australia.
It has nothing to do with Asian pollution being transported directly
over Australia.”
Dr.
Rotstayn says this implies that decreasing pollution
in Asia later this
century could reverse this
effect and lead to an increase in Australian drying trends.
“We
are really at the beginning of understanding the
trends but sooner or later these emissions will be cleaned up and then
a trend
of increasing rainfall in the northwest and centre could be reversed.
This is
potentially serious, because the northwest and centre are the only
parts of Australia
where
rainfall has been increasing in recent decades.”
Dr.
Rotstayn stresses that climate modeling is a valuable
tool for teasing out what is actually causing weather trends, rather
than
simply assuming that these trends are all related to greenhouse gases.
At
a time when Australian science agencies are investing
in new climate forecasting capabilities, the research – to be
published early
in 2007 in the Journal of Geophysical
Research – increases confidence in the accuracy of
future climate
simulations for Australia.
An
aerosol is a haze of particles in the atmosphere. Dr.
Rotstayn says representing aerosols in climate models and understanding
their
influence on cloud formation and rainfall is one of the biggest
challenges
facing climate scientists.
“Because
the cooling effect of aerosol pollution is
possibly comparable to the warming effect of increased levels of carbon
dioxide, the message from this research is that aerosols are an
essential
inclusion if we are to accurately describe present and future
Australian
climate,” he says.
The
new research is based on simulations performed with a
new low-resolution version of CSIRO’s global climate model
– including a
treatment of aerosols from both natural and human-induced sources.
##
Contact:
Craig
Macaulay
CSIRO Australia
61-362-325-219
craig.macaulay@csiro.au
This
text derived from:
http://www.csiro.au/csiro/content/standard/ps2l5.html
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