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  3. The climate of earth has fluctuated quite a bit over the last 4.6 billion years of our planet’s history and it can be expected t

The climate of earth has fluctuated quite a bit over the last 4.6 billion years of our planet’s history and it can be expected t

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问题     The climate of earth has fluctuated quite a bit over the last 4.6 billion years of our planet’s history and it can be expected that the climate will continue to change. One of the most intriguing questions in earth science is whether the periods of ice ages is over or are we living in an "interglacial", or period of time between ice ages?
    The geologic time period we are now living in is known as the Holocene. This epoch began about 11,000 years ago which was the end of the last glacial period and the end of the Pleistocene epoch. The Pleistocene was an epoch of cool glacial and warmer interglacial periods which began about 1.8 million years ago.
    Since the glacial period known as the "Wisconsin" in North America and "Warm" in Europe when over 10 million square miles( about 27 million k㎡) of North America, Asia, and Europe were covered by ice, almost all of the ice sheets covering the land and glaciers in the mountains have retreated. Today about ten percent of the earth’s surface is covered by ice; 96% of this ice is located in Antarctica and Greenland. Glacial ice is also present in such diverse places as Alaska, Canada, New Zealand, Asia, and California.
    As only I1,000 years has passed since the last Ice Age, scientists can not be certain that we are indeed living in a post-glacial Holocene epoch instead of an interglacial period of the Pleistocene and thus due for another ice age in the geo logic future. Some scientists believe that an increase in global temperatare, as we are now experiencing, could be a sign of an impending ice age and could actually increase the amount of ice on the earth’s surface.
    The cold, dry air above the Arctic and Antarctica carries little moisture and drops little snow on the regions. An in crease in global temperature could increase the amount of moisture in the air and increase the amount of snowfall. After years of more snowfall than melting, the Polar Regions could accumulate more ice. An accumulation of ice would lead to a lowering of the level of the oceans and there would be further, unanticipated changes in the global climate system as well.
    Our short history on earth and oar shorter record of the climate keeps us from fully understanding the implications of global warming. Without a doubt, an increase in the earth’s temperature will have major consequences for all life on this planet.
选项 A、Has the Pleistocene Epoch Ended?
B、Another Ice Age in the Aeologle Futurn Is Coming?
C、The Ice Ages: Are They Over?
D、Glacial Ice Will Be Present in Different Places?
答案C
解析 主旨大意题。文章的第一段谈到了科学家们提出厂冰期是否结束，我们是否处于间冰期。接下来分析了更新世纪冰期的历史、开始的时间、特点以及地球升温可能会引起地球的变化，然而对于我们到底处于什么样的地质时期，没有做出肯定的结论。
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