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  3. In the United States the science of climate change still remains a controversial issue. Part of the problems is that it is compl

In the United States the science of climate change still remains a controversial issue. Part of the problems is that it is compl

admin2010-09-10  57
问题     In the United States the science of climate change still remains a controversial issue. Part of the problems is that it is complex and hard to isolate its parts. We do know how vital it is to life. The atmosphere forms a gaseous, protective envelope around earth protecting the earth from the cold of space, from harmful ultraviolet light, and from all but the largest meteors. After traveling over 93 million miles, solar energy strikes the atmosphere and earth’s surface, warming the planet and creating what is known as the "bio sphere" which is the region of earth capable of sustaining life. Atmospheric circulation is one important reason that life on earth can exist at higher latitudes because equatorial heat is transported poleward, moderating the climate.
    The atmosphere is not just a protector but also a great transporter. The transport of water vapor in the atmosphere is an important mechanism by which heat energy is redistributed poleward. Heat energy absorbed at the equator is deposited at the poles and the temperature gradient between these regions is reduced. The circulation of the atmosphere and the weather it generates is but one example of the many complex, interdependent events of nature. The web of life depends on the proper functioning of these natural mechanisms for its continued existence.
    Some argue that climate change is too complicated to be attributed only to human activity. For example, fossil studies of radiolaria, a group of one-celled animals characterized by silicon-containing shells, have given scientists a fairly accurate account of climatic conditions in the distant past. Geologists found these 450,000-year-old microorganisms pre served in cores of sediment taken beneath the floor of the Indian Ocean. They provide a re cord of cycles of climatic changes, determined by the alternating layers of species of warm and cold-preferring radiolaria. We now have confirmation that changes in the earth’s orbital geometry caused the ice ages.
    This does not let us off the hook because although we can hardly alter the basic forces at work that alter climate, even small contributions by humans can have dramatic effects. Given nature’s interconnectedness, it is possible that the most serious threats have yet to be recognized.
According to the text, fossil studies of radiolaria are significant because they.
选项 A、live in the depths of the ocean
B、are one-celled
C、have survived through the ages
D、demonstrates climatic changes prior to humans
答案D
解析 属信息推断题。第三段讲到放射虫的化石研究这个例子，目的是为了证明本段主题即第一句话，“气候变化过于复杂，不能只归因于人类活动”。则证明在人类出现之前已经有气候的变化了。
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