Climate change: world round-up
The seven continents and their climate challenges.
There are few certainties where climate change is concerned. And even relatively straightforward predictions (sea levels, temperatures and global precipitation are all set to rise) will have complex and surprising effects that vary from place to place. So who will be the winners and losers? News@nature.com surveys the seven continents to find out.
As Europe warms, the north of the continent is tipped to gain a more 'Mediterranean' climate, while the Mediterranean countries themselves swelter through increasingly frequent droughts. Potentially good news, then, for British grape-growers, who are starting to focus their attentions on the market for fizz as northern France's Champagne region grows warmer. But bad news for agriculture elsewhere, not to mention the ski resorts of the Alps.
Traditional tourism hot spots such as Spain and Greece could find that their summer temperatures are simply too sizzling, tempting holidaymakers to vacation further north. Extreme heatwaves such as the one that struck western Europe in 2003 are set to increase in frequency in a warming world (see ' Extreme heat on the rise'), causing wildfires, loss of crops, and a rise in summer deaths.
Phil Jones, director of the Climate Research Unit at the University of East Anglia in Norwich, UK, points out that adapting to similar extremes in future will mean wider use of air conditioning. This will boost power use and make it more difficult for governments to meet the greenhouse emission targets set by the Kyoto Protocol.
Industries that rely on melt water from winter snows could be hit hard by temperature rises that cause more of this precipitation to fall as rain. Agriculture on the US west coast, for example, depends on the spring runoff of water from the Rocky Mountains to sustain crops through the parched summer. If this water arrives early as rain, rather than wintering in the mountain tops, then farmers and hydroelectric engineers may have to adapt to marshal these resources.
"Effectively, you could be losing a free reservoir," says Nigel Arnell, who studies water and climate at the University of Southampton, UK.
The melting of Arctic ice is causing concern for ecosystems in the north of the continent. The northern coasts of Canada and neighbouring Greenland spend much of their year mired in the polar ice cap. And environmentalists are worried that polar bears could be big losers if this ice begins to fragment or pull away from the mainland, leaving them unable to patrol large territories in search of food.
The climate of South America's long, snaking landmass is heavily influenced by the swirling currents of the Pacific Ocean that lies alongside it, not least during El Niño events. In these periods, cool waters are replaced by warmer waters drifting across from the west, killing fish and causing more rain to fall on the South American coast. Such events are predicted to grow more frequent.
But the South Atlantic Ocean could have more important effects on the continent's climate in a warming world, Jones points out. In 2004, the Brazilian state of Santa Catarina was hit by a huge tropical storm, often called 'the nameless hurricane'. It lacked an official sobriquet because weather experts had not expected the relatively cool southern Atlantic to be capable of triggering a ferocious tropical storm, of the kind fuelled by evaporating waters in the warmer North Atlantic. That may be set to change.
The severity of monsoon rains are expected to increase, which may mean yet more flooding for the inhabitants of low-lying countries such as Bangladesh.
But to the east, regions such as Indonesia and the Pacific Rim are expected to receive less rain as El Niño events grow more frequent and divert warm waters, which feed rain clouds, towards South America.
Siberian residents will be affected by the melting of permafrost, the layer of soil that remains perpetually frozen. Worried locals have already noticed buildings listing alarmingly to one side as the southern boundary of the permafrost moves north: the thaw leaves the buildings moored in nothing but squelchy earth for part of the year.
The Asian landmass itself has a huge influence on a vital part of the climate cycle: ocean circulation. Its mighty rivers feed fresh water into the Arctic Ocean, which is one of the major sources of cold, heavy water that sinks down and drives currents around the globe. The more lightweight, fresh water that empties here, the more likely major ocean currents are to slow down.
Africa, home of the world's largest desert, the Sahara, is more at risk than most from the dangers of encroaching desertification. Although overall global rainfall is predicted to increase, drought-prone regions look set to expand as rising temperatures strangle plant communities that previously helped to retain water in the soil. This could have disastrous impacts on food production for the continent.
In sub-Saharan Africa, meanwhile, increasing tropical rainfall could exacerbate the problem of malaria, already responsible for around a million deaths every year. The mosquitoes that carry the malaria pathogen thrive on stagnant ponds of water; more rain could mean more mosquitoes and more disease.
This almost relentlessly dry continent stands to become even more so if El Niño events become commonplace.
Warming of ocean waters has already damaged the Great Barrier Reef, the world's largest living structure. Since 1998, the reef has undergone two 'bleaching' events, in which huge numbers of corals throw off the coloured algae that live alongside them, as a result of stress caused by rising temperatures.
In the interior, Australia's sporty inhabitants may soon have to go elsewhere in search of snow. "The ski industry in Australia has not got long left," predicts Jones. Warming temperatures around the world are forcing resorts to be built at higher and higher altitudes. But Australia, with its hot climate and lack of a large mountain range, is running out of room. "They can't go any higher," he says.
Antarctica, whose status as a protected wilderness gives it the highest proportion of scientists of any of the seven continents, is of huge interest to climatologists. It has the potential to influence the world's climate for both good and bad.
Many researchers fear the break up of the West Antarctic ice sheet, which would dump huge amounts of fresh water into the ocean and raise sea levels by as much as several metres over the coming century.
But additional precipitation could mean that Antarctica's frozen wastelands grow in size, as more and more snow falls in the centre, locking up water that would otherwise end up in the ocean. "There could even be a reduction in sea level," says Arnell.
Whatever happens to the sea level, warming waters are expected to disrupt growth of krill. These tiny creatures are one of the fundamental food sources for life in the Antarctic, and supplement fish, chicken and cattle feed worldwide.
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