问题补充：
In the atmosphere, carbon dioxide acts rather like a one-way mirror or the glass in the roof of a greenhouse which allows the suns 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 (北半球), possibly resulting in an alteration of the earths 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 gone beyond 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 (使旋转), every 27. 5 days, it presents hotter or colder faces to the earth, and different aspects to different parts of the earth. This seems to have a considerable effect on the distribution of the earths atmospheric pressure, and consequently on wind circulation. The sun is also changeable over a long term: its heat output goes up and down in cycles, the latest trend being downward.
Scientists are now finding shared relations between models of solar weather interactions and the actual climate over many thousands 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 (惯性) of the earths climate. If this is right, the warming effect of carbon dioxide might thus be serving as a useful opposed balance to the suns fading heat .
【小题1】It can be concluded that a concentration of carbon dioxide in the atmosphere would.A．mean a warming-up in the AntarcticB．raise the temperature of the earth s surfaceC．prevent the suns rays from reaching the earths surfaceD．explain the cause of great changes in the climate in the northern hemisphere【小题2】The article was written to explain . A．the greenhouse effectB．the solar effects on the earthC．the causes affecting weatherD．the models of solar-weather interactions【小题3】Although the fuel consumption is greater in the northern hemisphere, temperatures thereseem to be falling. This is.A．mainly because the levels of carbon dioxide are risingB．partly due to changes in the output of solar energy C．possibly because the ice caps in the poles are meltingD．only due to the effect of the inertia of the earth s climate【小题4】 On the basis of their models, scientists believe the opinion that.A．the climate of the world should be becoming coolerB．the new Ice Age will be delayed by the greenhouse effectC．the man-made warming effect helps to increase the solar effectsD．it will take thousands of years for the inertia of the earths climate to take effect【小题5】 If the assumption about the delay of a new Ice age is correct, .A．ice would soon cover the northern hemisphereB．the greenhouse effect could work in favor of the earthC．the best way to overcome the cooling effect would be to burn more fuelsD．the increased levels of carbon dioxide in the atmosphere could warm up the earth even more quicklyB
答案：
(答案→)B
解析：[文章大意]这是一篇科普文，分析全球变暖的真正原因，到底是因为人类生活排放的二氧化碳还是因为太阳活动，今天的天气状况并没有印证若干年前的科学预测。
【小题1】细节理解题。由文章第一段可知大量二氧化碳集中在一起，会使地球表面的温度升高。因为二氧化碳的作用就象单向的镜子或者温室的玻璃屋顶一样只允许阳光进来，而里面的热却无法散去。
【小题2】主旨大意题。文章第一至第四段解释二氧化碳对全球气候的影响，而第五、六段又怀疑二氧化碳的作用，分析太阳活动对全球变暖的影响。由此看来，文章的目的是解释影响天气的原因。
【小题3】细节理解题。文章第五段提出北半球消耗燃料多，排放的二氧化碳量大，按道理北半球气候应升高但实际反而下降，什么原因？第六段从太阳活动解释了上述疑问：可能部分是由于太阳能量释放的不同。
【小题4】细节理解题。由最后一段第二句”The problem is that the models are predicting that the world should be entering a new Ice Age and it is not”可以推测科学家认为地球气候应变冷，而入新的冰河时期。
【小题5】推理判断题。如果新的冰河时期推迟的假设正确，可能是因为地球表层的二氧化碳起的保温作用。
