Melting Glaciers Several glaciers in the Alps have already disappeared in as few as 40 year. In the Patagonian ice fields of

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问题                         Melting Glaciers
    Several glaciers in the Alps have already disappeared in as few as 40 year. In the Patagonian ice fields of Argentina, some glaciers have receded one and one-half kilometers in the last 13 years, In the Himalayan Mountains, glaciers are melting so fast that runoff sometimes floods the surrounding areas. Their fate is a preview of the future of other glaciers on Earth.
    The shrinking of the world’s glaciers will have massive consequences for communities that depend on ice melt for their water. In the short-term, these consequences may appear beneficial. For example, extra water from glaciers means that hydroelectric dams will run at maximum power. In the long run, however, the melting of Earth’s glaciers could be catastrophic. Today’s extra hydroelectric power has been stolen from the future. Communities with ample power now may have none after the glaciers have melted and have stopped filling reservoirs. Likewise, water for irrigation, drinking, transportation, and nuclear power stations will slow to the levels provided solely by rainfall. The loss of ice will increase sea levels worldwide.

    Temperature change and a lack of snow is causing the retreat of the glaciers. According to many scientists, our plant is getting warmer. In the Alps, for example, temperatures have risen an average of 1-1.5 degrees Celsius (1.8-3 degrees Fahrenheit) since 1850. During the same period, Alpine glaciers in Switzerland have lost about half of their volume. Likewise, temperatures have changed in the Tien Shan Mountains in southern Kazakhstan. Researchers there have discovered a small rise in temperature, 0.5 degrees Celsius, over the last 50 years and even this is enough to reduce glaciers dramatically over time.
    As temperatures have increased, precipitation has decreased. Glaciers no longer build up during snowy winter months which also contributes to their decrease in size over in the long run.
    The warming of our globe is often blamed on human activity, such as the burning of fossil fuels, especially in industrialized nations. Automobile emissions and industrial waste are increasing the quantity of greenhouse gases in our atmosphere, possibly causing increased temperatures. However, scientists have not definitively tied human activity to the current temperature rise.
    Some scientists argue that global warming may be a normal trend of the Earth’s temperature violations. One theory argues that we are near the end of a so-called "Little Ice Age" , and that the retreat of the glaciers is a natural result of this cycle. Whether natural or produced by humans, there is little hope for the immediate future of glaciers as we know them.
    Complete the summary below by choosing no more than three words from the passage.
    Around the world, glaciers are disappearing. This disappearance is caused by a rise in the Earth’s【71】______and a lack of precipitation. Some scientists think that global warming is a natural【72】______in the Earth’s climate. Others believe that human use of【73】______traps greenhouse gases in the atmosphere and increases temperatures. Either way, the rapid shrinking of glaciers will have massive【74】______for our planer. At first, some of these changes may appear【75】______, such as increased production of hydroelectric power. Over time, however, glacial melting could be devastating.

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答案trend

解析 (由本文可知关于全球变暖,有两个猜测:人类燃烧化石燃料(第五段第一句The warming of our globe is often blamed on human activity,such as the burning of fossil fuels,especially in industrialized nations)和全球气温的自然变化(第六段第一句Some scientists argue that global warming may be a normal trend of the Earth’s temperature violations),故可知此处为第二个原因。)
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