Passage Two?

　　Questions 26 to 30 are based on the following passage:

　　In the atmosphere, carbon dioxide (二氧化碳) acts rather like a one-way mirror—the glass in the roof of a greenhouse which allows the sun′s rays to enter but prevents the heat from escaping.?According to a weather expert′s prediction, the atmosphere will be 3℃ warmer in the year 2050 than it is today, if man continues to burn fuels at the present rate. If this warming up took place, the ice caps in the poles would begin to melt, thus raising sea level several metres and severely flooding coastal cities, Also, the increase in atmospheric temperature would lead to great changes in the climate of the northern hemisphere, possibly resulting in an alteration of the ?earth′s-chief food-growing zones.?

　　In the past, concern about a man-made warming of the earth has concentrated on the Arctic because the Antarctic is much colder and has a much thicker ice sheet. But the weather experts are now paying more attention to West Antarctic, which may be affected by only a few degrees of warming: in other words, by a warming on the scale that will possibly take place in the next fifty years from the burning of fuels. Satellite pictures show that large areas of Antarctic ice are already disappearing. The evidence available suggests that a warming has taken place. This fits the theory that carbon dioxide warms the earth.?

　　However, most of the fuel is burnt in the northern hemisphere,where temperatures seem to be falling. Scientists conclude,therefore, that up to now natural influences on the weather have exceeded those caused by man. The question is: Which natural cause has most effect on the weather??

　　One possibility is the variable behavior of the sun. Astronomers at one research station have studied the hot spots and ?"cold"? spots(that is, the relatively less hot spots) on the sun.As the sun rotates, every 27.5 days, it presents hotter or ?"colder"? faces to the earth, and different cet6w.com parts of the earth. This seems to have a considerable effect on the distribution of the earth′s atmospheric pressure, and consequently on wind circulation. The sun is also variable over a long term: its heat output goes up and down in cycles, the latest trend being downward.?

　　Scientists are now finding mutual relations between models or solar-weather interactions and the actual climate over many thousand of years, including the last Ice Age. The problem is that the models are predicting that the world should be entering a new Ice Age and it is not. One way of solving this theoretical difficulty is to assume a delay of thousands of years while the solar effects overcome the inertia of the earth′s climate. If this is right, the warming effect of carbon dioxide might thus be serving as a useful counter-balance to the sun′s diminishing heat.?

　　26. It can be concluded that a concentration of carbon dioxide in the atmosphere would .?

　　A) prevent the sun′s rays from reaching the earth′s surface?

　　B) mean a warming up in the Arctic?

　　C) account for great changes in the climate in the northern hemisphere?

　　D) raise the temperature of the earth′s surface?

　　27. The article was written to explain .?

　　A) the greenhouse effect?

　　B) the solar effects on the earth?

　　C) the models of solar?weather interactions?

　　D) the causes affecting weather?

　　28. Although the fuel consumption is greater in the northern hemisphere, temperatures there seem to be falling. This is .?

　　A) mainly because the levels of carbon dioxide are rising?

　　B) possibly because the ice caps in the poles are melting?

　　C) exclusively due to the effect of the inertia of the earth′s climate?

　　D) partly due to variations in the output of solar energy?

　　29. On the basis of their models, scientists are of the opinion that .?

　　A) the climate of the world should be becoming cooler?

　　B) it will take thousands of years fro the inertia of the earth′s climate to take effect?

　　C) the man?made warming effect helps to increase the solar effect?

　　D) the new Ice Age will be delayed by the greenhouse effect?

　　30. If the assumption about the delay of a new Ice Age is correct, .?

　　A)the best way to overcome the cooling effect would be to burn more fuels

　　B) ice would soon cover the northern hemisphere?

　　C) the increased levels of carbon dioxide in the atmosphere could warm up the earth even more quickly?

　　D)the greenhouse effect could work to the advantage of the earth?

　　26. 文章第一段講到二氧化碳在大氣中就像溫室的玻璃屋頂一樣吸收太陽的光線并阻擋光熱的流失，文章第三段最后一句話又再次提到二氧化碳能使地球變熱的理論。因此，正確答案為D)。

　　27. 全文講述的是影響天氣的諸多原因。選項(xiàng)A)，B)，C)在文中均被提及但不足以概括全文的主旨，只有D)是比較全面的。

　　28. 文章第四段提及這一現(xiàn)象時(shí)講到，科學(xué)家們認(rèn)為： 這一現(xiàn)象的產(chǎn)生是因?yàn)榈侥壳盀橹棺匀唤鐚μ鞖獾挠绊懸�大于人類對天氣的影響。而究竟是哪種自然力量對天氣的影響最大呢? 文章第五段第一句話給出了答案：其中一個(gè)可能就是太陽的不斷變動。選項(xiàng)D)與此意相符。

　　29. 文章最后一段提到科學(xué)家們模擬太陽與天氣之間的相互作用，并試圖找出這種模擬與數(shù)千年來真正的氣候之間的相互關(guān)系。此段第二句講到：這些模擬結(jié)果都預(yù)測全球會進(jìn)入一個(gè)新的冰河時(shí)代。所以，選項(xiàng)A)應(yīng)為正確答案。

　　30. 本題涉及對文章最后一段最后一句話的理解。 如果有關(guān)太陽光能延緩新冰河時(shí)代到來的推測是正確的，那么二氧化碳的溫室效應(yīng)將發(fā)揮有效的作用來平衡太陽日益減少的光熱。選項(xiàng)D)與此意相符。