单选题
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 wanning 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.
单选题
Which of the following is true of global wanning 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.
【正确答案】
B
【答案解析】[解析] 细节题。根据题干定位到第一段。该段第一句话指出几十年前人们就已经熟知北冰洋海冰正在消融的事实，接下来第二句话指出除了少数气候学家外，几乎所有的气候学家都认为海冰消融是由全球气候变暖造成的(the underlying cause is believed by an but a handful of climatologists to be global warming)，故B项“大多数气候学家将北极海水消融归因于全球气候变暖”与原文相符，为正确答案。
单选题
According to Paragraph 2, the feedback loop A. makes the wanning 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 wanning all over the world.
【正确答案】
C
【答案解析】[解析] 细节题。根据题干定位到第二段。该段第三、四句具体解释了反馈循环，即与冰雪相比，颜色较深的陆地与海水吸收的热量多。反射的热量少，因而冰雪融化后露出陆地和海洋会加速局部变暖，继而再导致冰雪消融(the darkness of land and water...absorbs more heat from the sun and reflects less of it back into space)。由此推知，反馈循环就是海冰消融，露出颜色较深的陆地和海水，吸取更多的太阳热量，加速海冰消融，故C项与原文相符，为正确答案。
单选题
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.
【正确答案】
A
【答案解析】[解析] 细节题。根据题干定位到第三段。该段第一句话承接第二段，指出北极海冰迅速消融的另一个原因，即冰体本身的物理变化(physical change in the ice itself)。第二句话指出先前冰体巨大而坚固，只是在其边缘部分发生融化和再次冻结，现在冰层变薄变脆，因此更容易融化(now thinner, more fractured, and so more liable to melt)，故A项符合文意，为正确答案。
单选题
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.
【正确答案】
B
【答案解析】[解析] 推断题。根据题干关键词the United Nations Environment Program定位到第四段。第二、三句均是关于联合国环境规划署发布的一份报告的内容(a recent report by the United Nations Environment Program)，该报告表明，如果避免农作物燃烧以及森林火灾，停止使用柴油发动机以及燃烧木柴的炉具等做法能够在全球范围内被广泛应用的话，截至2050年，全球变暖的速度将减缓一半(if such measures...were adopted everywhere they could halve the wider rate of wanning by 2050)。也就是说，每个国家都可以做出一些贡献来缓和全球气候变暖，故B项符合文意，为正确答案。
单选题
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.