Climatic conditions are delicately adjusted to composition 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, CO2, in the atmosphere has an important effect on climatic change. Most of the Earth's incoming energy is short-wavelength radiation (短波辐射) , which tends to pass through atmospheric CO2 easily. The Earth, however, reradiates much of the received energy as long-wavelength radiation (长波辐射), which CO2 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 composed mostly of CO2, whose surface temperatures have been measured at 430~C.If the CO2 content of the atmosphere is reduced, the temperature falls. According to one respectable theory, if the atmospheric CO2 concentration were halved, the Earth would become completely covered with ice. Another equally respectable theory, however, states that a halving of the CO2 concentration would lead only to a reduction in global temperatures of 3℃.
If, because of an increase in forest fires or volcanic activity, the CO2 content of the atmosphere increased, a warmer climate would be produced. Plant growth, which relied on both the warmth and the availability of CO2, would probably increase. As a consequence, plant would use more and more CO2. Eventually CO2 levels would decrease and the climate, in turn, would become cooler. With reduced temperatures many plants would die; CO2 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 CO2 present in the atmosphere, with regular temperature increase and decrease.
Some climatologists argue that the burning of fossil fuels has raised the level of CO2 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 CO2 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 CO2 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 CO2 on atmospheric radiation
C. discussing effects that changes in the CO2 level in the atmosphere might have on climate
D. challenging hypotheses (假说) about the effects of water vapor and CO2 on climate
53. The passage suggests that a large decrease in the amount of CO2 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 CO2 increases
D. support the argument that the CO2 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 CO2 1evel in the atmosphere
D. slight regional temperature changes can be considered an abnormal feature (特征) of the environment
科教类阅读的概念：
科教类阅读主要考查考生对书面语篇的整体领悟能力和接受及处理具体信息的能力。试题的取材，密切联系当前我国和世界经济、科技等方面的变化，有关数据的来源真实可信。
科教类文章阅读技巧：
一、材料特点：
这类文章的总体特点是：科技词汇多，句子结构复杂，理论性强，逻辑严谨。具体说来它有以下几个特点：
1、文章中词汇的意义比较单一、稳定、简明，不带感情色彩，具有单一性和准确性的特点。这类文章通常不会出现文学英语中采用的排比、比喻、夸张等修辞手法，一词多义的现象也不多见。
2、句子结构较复杂，语法分析较困难。为了描述一个客观事物，严密地表达自己的思想，作者经常会使用集多种语法现象于一体的长句。
3、常使用被动语态，尤其是一些惯用被动句式。
二、命题特点：
科普类阅读的主要命题形式有事实细节题、词义猜测题、推理判断题以及主旨概括题等，其中推理判断题居多。
三、应对策略：
1、要想做好科普英语阅读理解题，同学们就要注意平时多读科普知识类文章，学习科普知识，积累常见的科普词汇，从根本上提高科普英语的阅读能力。
2、要熟悉科普类文章的结构特点。科普类文章一般由标题(Head line)，导语(Introduction)，背景(Back ground)，主体(Main body)和结尾(End)五部分构成。标题是文章中心思想高度而又精辟的概括，但根据历年的高考情况来看，这类阅读理解材料一般不给标题，而要同学们选择标题。导语一般位于整篇文章的首段。背景交待一个事实的起因。主体则对导语概括的事实进行详细叙述，这一部分命题往往最多，因此，阅读时，同学们要把这部分作为重点。结尾往往也是中心思想的概括，并与导语相呼应，命题者常在此要设计一道推理判断题。
3、在进行推理判断时，同学们一定要以阅读材料所提供的科学事实为依据，同时所得出的结论还应符合基本的科普常识。
科普类阅读应试策略：
【命题趋势】
阅读理解题主要考查考生对书面语篇的整体领悟能力和接受及处理具体信息的能力。试题的取材，密切联系当前我国和世界经济、科技等方面的变化，有关数据的来源真实可信。因此科普知识类文章是每年的必考题。分析历年的科普类文章我们不难发现以下特点：
1、文章逻辑性强，条理清楚，语法结构简单，用语通俗。
2、文章内容注重科技领域的新发现。内容新颖，从而使文章显得陌生，内容抽象复杂。
3、命题方面注意对具体细节的准确理解和以之为依据的推理判断。
4、以人们的日常行为或饮食健康入手，探讨利弊，诠释过程，阐述概念。
【应试对策】
许多考生在考试时感到困惑的是：为什么一些没有超越中学语法和词汇范围的篇章，读起来却不能正确理解，或者要花费很多时间才能读懂呢？这种现象的产生与阅读方法有很大的关系。例如，有的考生在考试时一见到文章就立刻开始读，结果读了半天，还不知道短文讲的是什么，试题要求了些什么，结果浪费了大量的时间，而阅读效果并不好。那么，怎样读效果才好呢？任何一种阅读方法或技巧的使用，都是由篇章特点和试题本身的要求决定的，应根据不同的体裁和试题要求采取不同的策略。
1、浏览。浏览的主要目的就是确定文章的体裁。如果文章属于人物传记、记叙文、故事、科普小品和有关社会文化、文史知识的文章，一般来说，应该先看看文章的试题考查内容，对题目类型做到心中有数，针对不同问题，在通读时有粗有细地去阅读，这样不仅能把握篇章的基本结构和逻辑线索，也能做好有关具体事实信息考查的试题。
2、挖掘寓意，掌握中心思想，推出结论。任何文章，作者在行文时都有一定的写作目的和主要话题。在通读篇章时应该吃透作者的写作意图，抓住文章的主题句，充分发挥自己的想象力和概括力，作出对中心思想的归纳和结论的推断。
3、把握篇章结构，利用上下文进行推测。高考中的阅读理解篇章往往是一个较完整的短文，其结构、思想，前后上下连贯统一。考试时应充分利用这一特点推测一些生词、短语在句中的含义，切莫盲目孤立猜测。
4、综观全篇，前后呼应。这是阅读理解的最后一步，在做完阅读理解题后，要立足于文章整体，再迅速读一遍短文，短文中的问题和答案的设置前后都是相关联的，有着一定的连续性，体现着文章的基本脉络。
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A. Popularity of Science Fiction |
80. |
Amongst the most popular books being written today are those which are usually classified as science fiction. Hundreds of titles are published every year and are read by all kinds of people. Furthermore, some of the most successful films of recent years have been based on science fiction stories.
81. |
It is often thought that science fiction is a fairly new development in literature, but its ancestors can be found in books written hundreds of years ago. These books were often concerned with the presentation of some form of ideal society, a theme which is still often found in modern stories.
82. |
Most of the classics of science fiction, however, have been written within the last hundred years. Books by writers such as Jules Verne and H.G. Wells, to mention just two well-known authors,
have been translated into many languages.
83. |
Modern science fiction writers don't write about men from Mars or space adventure stories. They are more interested in predicting the results of technical developments on society and the human mind; or in imagining future worlds which are a reflection of the world which we live in now.
Because of this their writing has obvious political undertones.
84. |
In an age where science fact frequently overtakes science fiction, the writers may find it difficult to keep ahead of scientific advances. Those who are sufficiently clear-sighted to see the way we are going, however, may provide a valuable lesson on how to deal with the problems which society will inevitably face as it tries to master its new technology.