A disaster in the making

A

Most scientists agree that global warming presents th greatest threat to the environment. There is little doub that the Earth is getting warmer. In the last century the average temperature rose about 0.6 degrees C around the world. From the melting of the ice cap on Mt Kilimanjaro, Africa's tallest peak, to the loss of coral reefs as oceans become warmer, the effects of global warming are often clear. Many experts warn that global warming will cause sea levels to rise dramatically. In the past 100 years the oceans have risen 10 to 20 cms - but that's nothing compared to what would happen if, for example, Greenland's massive ice sheet were to melt. The consequences would be catastrophic," says

Jonathan Overpeck, Director of the Institute for the Study of Planet Earth at the University of Arizona. "Even with a small sea level rise, we're going to destroy a number of nations and cultures that have existed for thousands of years. Overpeck and his colleagues have used computer models to create a series of maps that show the places most at risk of flooding.

B

Just as the evidence is clear that temperatures have risen in the last century, it's also well established that 26 carbon dioxide in the Earth's atmosphere has Increased about 30 percent, allowing the atmosphere to trap too much heat. However, the exact link, if any, between the increase in carbon dioxide emissions and the higher temperatures is still being disputed. Most scientists believe that humans, by burning fossil fuels such as coal and petroleum, are largely to blame for the increase in carbon dioxide. But some scientists also point to natural causes, such as volcanic activity. 'Many uncertainties surround global warming,' says Ronald Stouffer at the US National Oceanic and Atmospheric Administration's Geophysical Fluid Dynamics Laboratory. 'How much of it would still occur if humans were not changing the climate in any way?'

C

The current rate of warming is faster than ever before, however, which suggests it probably is not a natural occurrence. And a large number of scientists believe the rise in temperatures will, in fact, speed up. The UN Group on Climate Change reported in 2001 that the average temperature is likely to increase by between 1.4 and 5.8 degrees C by the year 2100. The climate change is likely to impact on ecosystems, agriculture and the spread of disease. 'Global warming is a serious threat to animal and plant life,' says Jay Malcolm, a forestry professor at the University of Toronto. 'As climates warm, more southerly species will begin appearing further north... species will find themselves in habitats where they don't belong. For example glaciers and sea ice in both the northern and southern hemispheres are already melting at a rapid pace, placing animals like polar bears at risk."

D

A recent study suggested that Greenland's ice sheet will begin to melt if the temperature there rises by three degrees C. That is something many scientists think is likely to happen in another hundred years. The complete melting of the Greenland ice cap would raise sea levels by seven metres. Even a partial melting would cause a one-metre rise. Such a rise would have a devastating impact on low-lying islands, such as the Maldives, which would be entirely submerged. Densely populated areas like the Nile Delta and parts of Bangladesh would become uninhabitable, affecting hundreds of millions of people. A one-metre sea-level rise would flood the eastern seaboard of the USA.

E 

Other scientists emphasise that such doomsday scenarios may be hundreds of years in the future. "You can't say with any certainly that sea-level rises are going to have a huge impact on society," says Stouffer "Who knows what the planet will look like 5000 years from now? Most climate scientists, however, agree that global warming is a threat that has gone unchecked for too long, 'Is society aware of the seriousness of climate warming? I don't think so, says Marianne Douglas, professor of geology at the University of Toronto. Otherwise we'd all be leading our lives differently. We'd see a society that used alternative sources of energy, with less dependency on fossil fuels


Look at headings bellow. Which is the best heading for each paragraph A-E?
The effect of global warming on plant and animal life
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Uncertainty among experts about the effects of global warming
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Global warming: the position now and predictions for the future
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The countries affected by the rise in sea level due to global warming
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The debate about the causes of global warming
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