【delicately】Climaticconditionsaredelicatelyadjustedtocompositionofthe...

Climatic conditions are delicately adjusted to position of the Earth's atmosphere. If there were a change in the atmosphere ― for example in the relative amounts of atmospheric gases ― the climate would probably change also. A slight increase in water vapor (蒸汽) for example would increase the heat-keeping capacity of the atmosphere and would lead to a rise in global temperatures. The level of carbon dioxide CO 2 in the atmosphere has an important effect on climatic change. Most of the Earth's ining energy is short-wavelength radiation (短波辐射) which tends to pass through atmospheric CO 2 easily. The Earth however reradiates much of the received energy as long-wavelength radiation (长波辐射) which CO 2 absorbs and then goes toward the Earth. This phenomenon known as the greenhouse effect can result in an increase in the surface temperature of a planet. An extreme example of the effect is shown by Venus a planet covered by heavy clouds posed mostly of CO 2 whose surface temperatures have been measured at 430~C.If the CO 2 content of the atmosphere is reduced the temperature falls. According to one respectable theory if the atmospheric CO 2 concentration were halved the Earth would bee pletely covered with ice.  Another equally respectable theory however states that a halving of the CO 2 concentration would lead only to a reduction in global temperatures of 3℃. If because of an increase in forest fires or volcanic activity the CO 2 content of the atmosphere increased a warmer climate would be produced. Plant growth which relied on both the warmth and the availability of CO 2 would probably increase. As a consequence plant would use more and more CO 2 .  Eventually CO 2 levels would decrease and the climate in turn would bee cooler. With reduced temperatures many plants would die; CO 2 would thus be returned to the atmosphere and gradually the temperature would rise again. Thus if this process occurred there might be a long-term oscillation (波动) in the amount of CO 2 present in the atmosphere with regular temperature increase and decrease. Some climatologists argue that the burning of fossil fuels has raised the level of CO 2 in the atmosphere and has caused a global temperature increase of at least 1℃. But a supposed global temperature rise of 1 ℃ may in reality be only several regional temperature increases restricted to areas where there are many meteorological (气象的) stations. Other areas for example the Southern Hemisphere oceanic zone may be experiencing an equal temperature decrease that is unrecognized because of the shortage of meteorological recording stations.   51. Which of the following questions does the information supplied in this passage try to answer? A. What are the steps in the process that takes place as CO 2 absorbs long-wavelength radiation? B. How might our understanding of the greenhouse effect be improved if the burning of fossil  were decreased? C. What might cause a series of regular increases and decreases in the amount of CO 2 in the atmosphere? D. Why are there fewer meteorological recording stations in the Southern Hemisphere oceanic zone than atmosphere? 52. The author is primarily concerned with ________. A. explaining the effects that the burning of fossil fuels might have on climate B. explaining the effects of CO 2 on atmospheric radiation C. discussing effects that changes in the CO 2 level in the atmosphere might have on climate D. challenging hypotheses (假说)  about the effects of water vapor and CO 2 on climate 53. The passage suggests that a large decrease in the amount of CO 2 in the atmosphere would result in _________. A. at least a slight decrease in global temperatures B. at the most a slight increase in short-wavelength radiation reaching the Earth C. a slight long-term increase in global temperatures D. a slight short-term increase in atmosphere water vapor content 54. The author refers to Venus primarily in order to _______. A. show that the greenhouse effect works on other planets but not on Earth B. show the degree to which Earth's atmosphere differs from that of Venus C. support the opinion that as water vapor increases the amount of CO 2 increases D. support the argument that the CO 2 level in the atmosphere has a significant effect on climate 55. The discussion of climate in the passage suggests that _________. A. climate is perfectly stable B. we are unable at present to measure global temperature changes precisely. C. the only cause of regional climatic fluctuations (波动) is the change in CO 2 1evel in the atmosphere D. slight regional temperature changes can be considered an abnormal feature (特征) of the environment