阅读理解   Add CO2 to the atmosphere and the climate will get warmer—that much is well established. But climate change and carbon aren't in a one-to-one relationship. If they were, climate modeling would be a cinch. How much the globe will warm if we put a certain amount of CO2 into the air depends on the sensitivity of the climate. How vulnerable is the polar sea ice; how rapidly might the Amazon dry up; how fast could the Greenland ice cap disintegrate? That's why models like those from the Intergovernmental Panel on Climate Change spit out a range of predictions for future warming, rather than a single neat number.
    One of the biggest questions in climate sensitivity has been the role of low-level cloud cover. Low-altitude clouds reflect some of the sun's radiation back into the atmosphere, cooling the earth. It's not yet known whether global warming will dissipate clouds, which would effectively speed up the process of climate change, or increase cloud cover, which would slow it down.
    But a new study published in the July 24 issue of Science is clearing the haze. A group of researchers from the University of Miami studied cloud data of the northeast Pacific Ocean over the past 50 years and combined that with climate models. They found that low-level clouds tend to dissipate as the ocean warms—which means a warmer world could well have less cloud cover. 'That would create positive feedback, a reinforcing cycle that continues to warm the climate,' says Amy Clement, the leading author of the Science study.
    The data showed that as the Pacific Ocean has warmed over the past several decades—part of the gradual process of global warming—low-level cloud cover has lessened. That might be due to the fact that as the earth's surface warms, the atmosphere becomes more unstable and draws up water vapor from low altitudes to form deep clouds high in the sky. (Those types of high-altitude clouds don't have the same cooling effect.) The Science study also found that as the oceans warmed, the trade winds—the easterly surface winds that blow near the equator—weakened, which further dissipated the low clouds. The question now is whether this process will continue in the future, as the world keeps warming.
单选题     The word 'cinch' (Line 3, Para. 1) probably means ______.
 
【正确答案】 A
【答案解析】词汇理解题。根据题干的提示，定位到文章第一段。文章指出，但是气候变化和碳并非是一对一的关系。倘若真是如此，那气候建模就变得“cinch”，单词cinch所在的条件状语从句呈现了前后相反的语言逻辑，根据本句的“一对一的关系”可知，cinch意为“容易的事情”，因此A选项为正确答案。
单选题     The first two paragraphs are written to show ______.
 
【正确答案】 C
【答案解析】事实细节题。文章的前两段并没有谈及用现有技术更容易确定气候模型，因此D选项错误。文中谈到的是低层云可以给地球降温，A选项错误。第二段指出，现在还不知道全球变暖是会驱散低层云，从而加快气候变化的进程，还是会增加云量，减慢气候变化的进程。据此可知，选项C正确。
单选题     The word 'haze' in Paragraph 3 is closest in meaning to ______.
 
【正确答案】 B
【答案解析】词汇理解题。通过第三段可知，“haze”在此处指的是前一段所提内容，即现在还不知道全球变暖是会驱散低层云，从而加快气候变化的进程，还是会增加云量，减慢气候变化的进程。因此“haze”在此处指的是“疑惑”，故正确答案为B选项。
单选题     The new study published in Science illustrates that ______.
 
【正确答案】 C
【答案解析】事实细节题。根据题干中的Science可以定位到原文第三段。文章指出，他们发现在太平洋变暖时，低层云逐渐消散——这意味着云量在变暖的世界会更少，据此可知，C选项为正确答案。
单选题     Which of the following statements is true according to the last paragraph? ______
 
【正确答案】 A
【答案解析】根据题干中的last paragraph定位到文章最后一段。最后一段讲到全球变暖会导致低层云减少，从而形成高层云，但是高层云不具备降低地球温度的效果，因此选项B错误。该段也没有明确表明环境变化与全球变暖的关系是否持续，因此选项D错误。选项C为曲解原文细节信息。根据贸易风，即在赤道附近向东的地面风减弱了，吹散了低层云，可知选项A正确。