Experts Warn on Expanding Tropics

Monday, 6 July 2009

by Anna Salleh ABC

For most Australians, who live in the south of the continent, the expanding tropics mean less rain (Source: Will Burgess/Reuters)

The globe's tropical zone is expanding rapidly and more research is needed to help humans adapt, urge Australian experts.

In a review of over 70 scientific papers, climate researchers, Professor Steve Turton and Dr Joanne Isaacs of James Cook University in Cairns have documented the rapid advance of the tropical zone.

"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," says Turton, who examined evidence from weather balloons, satellite imagery, sea surface temperatures and climate models.

"That's between 300 and 500 kilometres just in that short period of time."

Turton 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% of the world's biodiversity, very high infant mortality, high rates of tropical diseases and they make up around 20% of Gross World Product," he says.

Turton says Australia is the only the 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 increasingly," he says. "But very little money goes into tropical medicine, compared to general medicine."

Turton says only 7% 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.

Drought

Turton says that for most of 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, he says.

"Sydney will be more like Brisbane by the end of century," says Turton.

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.

Source: ABC Science News