[originaltext] Today I want to talk about the Earth’s last major climatic sh

游客2024-04-18  18

问题  
Today I want to talk about the Earth’s last major climatic shift, at the end of the last ice age.
    But first, let’s back up a moment and review what we know about climatic change in general. First, we defined "climate" as consistent patterns of weather over significant periods of time.
    In general, changes in climate occur when the energy balance of the Earth is disturbed. Solar emergy enters the Earth’s atmosphere as light and is radiated by the Earth’s surface as heat. Land, water, and ice each affect this energy exchange differently. The system is so complex that, to date, our best computer models are only crude approximations and are not sophisticated enough to test hypotheses about the causes of climatic change.
    Of course, that doesn’t keep us from speculating. For instance, volcanic activity is one mechanism that might affect climatic change. When large volcanoes erupt, they disperse tons of particles into the upper atmosphere, where the particles then reflect light. Since less light is entering the system of energy exchange, the result would be a cooling of the Earth’s surface.
    Of course, this is just one possible mechanism of global climate change. In all probability, a complete explanation would involve several different mechanisms operating at the same time.
10. How does the speaker begin her discussion?
11. What does the speaker mean by the phrase"the energy balance of the Earth?"
12. Why do meteorologists have difficulty testing hypotheses about climatic changes?

选项 A、By categorizing the world’s climate.
B、By defining the term "climate. "
C、By summarizing the previous lecture.
D、By referring to the weather map.

答案 B

解析 听力材料的开头具有一定的迷惑性。说话者说今天要讨论的话题是关于地球最后一次重大的气候变化,但首先要看看大家对气候一般性的了解。说话者两次用了first这个词,表示在讨论之前,要先给“气候”(climate)下个定义,正确答案是B。考生生听课堂教学的内容时,应注意把握一些提示性词语。
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