By Anna Salleh for ABC Science Online
ABC News Online, 6 July 2009
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The globe's tropical zone is expanding rapidly and by the end of the century, Sydney's climate will be more like Brisbane's is today, Australian experts say.
Climate researchers Steve Turton and Joanne Isaacs of James Cook University in Cairns reviewed more than 70 scientific papers and documented the rapid advance of the tropical zone.
Dr Turton examined evidence from weather balloons, satellite imagery, sea surface temperatures and climate models.
"The review suggests that the tropics have expanded over the last 25 to 30 years, between 2 and 5 degrees of latitude in both hemispheres," Professor Turton said.
"That's between 300 and 500 kilometres just in that short period of time."
He says given the impacts on everything from farming and healthcare to viticulture and tourism, much more research is needed to help respond to this change.
"The tropics have half the world's population, 80 per cent of the world's biodiversity, very high infant mortality, high rates of tropical diseases and they make up around 20 per cent of Gross World Product," he said.
Dr Turton says Australia is the only first world country that has a significant amount of tropical land mass, and yet investment in research does not reflect this.
"Around half of Australia is tropical and the proportion is increasing," he said.
"But very little money goes into tropical medicine, compared to general medicine."
Dr Turton says only 7 per cent of CSIRO's total budget goes into tropical Australia.
He says the call for more tropical research is supported by a recent review of Australia's innovation system.
Dr Turton says that for most Australians - who live in the southern half of the continent - the spread of the tropics will actually mean more drought because of the southward spread of the dry subtropical zone.
As humid temperate climate zones will be replaced by the dry subtropical zone, cities like Sydney will get more rain in the summer but less rain overall.
"Sydney will be more like Brisbane by the end of century," Dr Turton said.
He says the climate of Melbourne and parts of Tasmania will become more Mediterranean, with a hot dry season and more rain in winter, until the mid-latitude jet stream moves further south and rainfall misses Australia's landmass altogether.