UNIT 2

Text 1

That Arctic sea ice is disappearing has been known for decades. The underlying cause is believed by all but a handful of climatologists to be global warming brought about by greenhouse-gas emissions. Yet the rate the ice is vanishing confuses these climatologists' models. These predict that if the level of carbon dioxide, methane and so on in the atmosphere continues to rise, then the Arctic Ocean will be free of floating summer ice by the end of the century. At current rates of shrinkage, by contrast, this looks likely to happen sometime between 2020 and 2050.

The reason is that Arctic air is warming twice as fast as the atmosphere as a whole. Some of the causes of this are understood, but some are not. The darkness of land and water compared with the reflectiveness of snow and ice means that when the latter melt to reveal the former, the area exposed absorbs more heat from the sun and reflects less of it back into space. The result is a feedback loop that accelerates local warming. Such feedback, though, does not completely explain what is happening. Hence the search for other things that might assist the ice's rapid disappearance.

One is physical change in the ice itself. Formerly a solid mass that melted and refroze at its edges, it is now thinner, more fractured, and so more liable to melt. But that is(literally and figuratively) a marginal effect. Filling the gap between model and reality may need something besides this. The latest candidates are "short-term climate forcings". These are pollutants, particularly ozone and soot(also called "black carbon") that do not hang around in the atmosphere as carbon dioxide does, but have to be renewed continually if they are to have a lasting effect. If they are so renewed, though, their impact may be as big as CO2's.

Reducing soot would not stop the summer sea ice disappearing, but it might delay the process by a decade or two. According to a recent report by the United Nations Environment Program, reducing soot and ozone in the lower part of the atmosphere, especially in the Arctic countries of America, Canada, Russia and Scandinavia, could cut warming in the Arctic by two-thirds over the next three decades. Indeed, the report suggests, if such measures—preventing crop burning and forest fires, cleaning up diesel engines and wood stoves, and so on—were adopted everywhere they could halve the wider rate of warming by 2050.

The rapid melting of the Arctic sea ice, then, illuminates the difficulty of modeling the climate—but not in a way that brings much comfort to those who hope that fears about the future climate might prove exaggerated. When reality is changing faster than theory suggests it should, a certain amount of nervousness is a reasonable response.

1. Which of the following is true of global warming according to Paragraph 1?

[A] It is caused mainly by carbon dioxide emissions.

[B] Most climatologists attribute Arctic sea ice melting to it.

[C] It doesn't develop as climatologists' models have predicted.

[D] Arctic sea ice will soon disappear under its impact.

2. According to Paragraph 2, the feedback loop______.

[A] makes the warming process in Arctic area much faster than elsewhere

[B] results from the dark land and water in Arctic area

[C] causes the Arctic sea to absorb more heat from the sun

[D] speeds up the rate of global warming all over the world

3. Which of the following is true of the reasons mentioned in Paragraph 3?

[A] The physical change happened to ice makes it easier to melt.

[B] The physical change of ice is the leading cause of Arctic ice melting.

[C] The pollutants like ozone and soot are not as influential as CO2.

[D] Ozone and soot can exert an effect as long-lasting as CO2 does.

4. The report by the United Nations Environment Program suggests that______.

[A] cutting soot emission can prevent summer sea ice from melting

[B] every country can contribute to the alleviation of global warming

[C] Arctic countries should not develop heavy industry

[D] we can stop global warming by taking effective measures

5. Which of the following is the text mainly about?

[A] The difficulty of modeling Arctic sea ice melting.

[B] Control of soot emission throughout the world.

[C] Human's responsibility for global warming.

[D] Reasons and feasible solutions for Arctic sea ice melting.