July 6, 2009
Climate Change Expanding World’s Tropical Zones
An Australian study has found climate change is rapidly expanding the size of the world's tropical zone, threatening to bring disease and drought to heavily populated areas, AFP reported.
The tropics had widened by up to 310 miles in the past 25 years, researchers at James Cook University concluded after examining 70 peer-reviewed scientific articles.
In an effort to determine how global warming was impacting the tropical zone, the researchers looked at findings from long-term satellite measurements, weather balloon data, climate models and sea temperature studies.
They found that warming extended well beyond the traditional definition of the tropics"”the equatorial band circling the Earth between the Tropic of Cancer and the Tropic of Capricorn.
That meant the subtropical arid zone which borders the tropics was being pushed into temperate areas, with potentially devastating consequences, according to Professor Steve Turton.
He said these areas include heavily-populated regions of southern Australia, southern Africa, the southern Europe-Mediterranean-Middle East region, the south-western United States, northern Mexico, and southern South America.
He added that all of them are predicted to experience severe drying.
"If the dry subtropics expand into these regions, the consequences could be devastating for water resources, natural ecosystems and agriculture, with potentially cascading environmental, social and health implications," he said.
Tropical diseases such as dengue fever were likely to become more prevalent, Turton said.
He explained that some models predicted that the greatest increase in the annual epidemic potential of dengue would be into the subtropical regions, including the southern United States, China and northern Africa in the northern hemisphere, and South America, southern Africa, and most of Australia in the southern hemisphere.
The evidence showed climate change was already affecting wildlife and rainfall in Australia, which is in the grip of its worst drought in a century, according to James Cook University vice-chancellor Sandra Harding.
Changes to wind patterns shown in some studies meant that rain was now being dumped in the ocean south of the continent, rather than over land.
Harding said there was also evidence that many Australian animal and plant species are moving south in an attempt to track their preferred climatic conditions and that some "won't make it."
She suggested the world should get serious about finding solutions to problems caused by climate change in the tropics.
"Tropical climate conditions are expanding and the impact of this expansion is immense because the tropics are a big, complex and important zone of the world."
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