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Half of Earth may see big climate changes

Half of Earth may see big climate changes
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First Published: Wed, Mar 28 2007. 01 15 AM IST
Updated: Wed, Mar 28 2007. 01 15 AM IST
Global warming may alter the climate significantly across “large portions” of the Earth by 2100, forcing animals and plants to move and adapt, scientists said in the Proceedings of the journal, National Academy of Sciences.
As much as 39% of the Earth’s land may experience conditions unknown at present by the end of the century and 48% may lose existing patterns, researchers at the universities of Wisconsin and Wyoming said after analysing scenarios for increases in emissions of greenhouse gases.
The new and disappearing climate zones will cause some species to become extinct and force others to migrate, bringing them into areas they haven’t been exposed to and taking them away from contact with other organisms. “More carbon dioxide in the air means more risk of entirely new climates or climates disappearing,” lead author Jack Williams, a geographer at the University of Wisconsin-Madison, said in a statement.
The United Nations Intergovernmental Panel on Climate Change (IPCC) on 2 February predicted temperatures will rise between 1.1-6.4 degrees Celsius (2.0 to 11.5 degrees Fahrenheit) by 2100, largely as a result of human activity, including the emission of greenhouse gases.
While the IPCC forecasts temperature changes to be greater near the poles, new and disappearing climates in 2100 are more likely to be found in the tropics and subtropics because those areas currently have less annual variability in temperature, and so even small changes will be felt more, the researchers said.
New rainfall and temperature patterns are more likely to occur in places such as South America’s Amazon basin, West Africa and parts of India, Indonesia and northern Australia, according to maps published in the paper. Sudan, Somalia, patches of central Africa and the southeastern US will also be affected.
Existing climate zones may disappear from southern Mexico, the Andes and parts of northern Russia, central Asia, Indonesia, southern Australia and central Africa. The existing patterns will move towards the poles and the tops of mountain ranges, creating new conditions in equatorial areas. The scientists conducted a second analysis to account, more accurately, for species’ limited abilities to migrate.
The new analysis determined local climates were new or had disappeared by 2100 if they didn’t occur within 500km of similar present-day systems.
The resulting maps show that more localized climate systems may disappear from most of Africa, Indonesia, Central America and the northern half of South America, as well as northern Russia and North America and coastal parts of Australia. The same regions are also the most likely to gain new patterns.
“Tropical species may be particularly sensitive to 21st- century warming,” the researchers said in the paper. This “adds urgency to current conservation efforts.”
The IPCC based its temperature forecasts on a range of scenarios of gas emissions. The scientists in Wisconsin and Wyoming used two of those outlooks, one which envisions high emissions of greenhouse gases and one with lower emissions, and plugged them into a range of computer models to determine what climatic changes may take place in different parts of the world.
The researchers used two of the IPCC scenarios. The A2 scenario envisages the atmospheric concentration of carbon dioxide more than doubles to about 800 parts per million by 2100, from about 379 ppm in 2005, the most recent data available. The B1 scenario sees levels stabilizing just above 500 ppm.
Researchers are still trying to determine what effects the changing habitats and climate patterns will have, and on which species. Using the higher-emissions scenario, between 12% to 39% of the land surface may gain a new climate, and 10 to 48 percent may lose an existing climate pattern, they said. Under the lower-emissions model, both ranges stand at 4 to 20 percent.
“We don’t know which bad things will happen or which good things will happen,” Williams said. “We are in for some ecological surprises.”
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First Published: Wed, Mar 28 2007. 01 15 AM IST