阅读表达. According to a weather expert's prediction, the atmosphere will be 3℃ warm

阅读表达。

According to a weather expert's prediction, the atmosphere will be 3℃ warmer in the year 2050 than it is today, if man continues to burn fuels at the present rate．If this warming up took place, the ice caps in the poles would begin to melt, thus raising sea level several meters and severely flooding coastal cities．

In the past, concern about a man-made warming of the earth has concentrated on the Arctic because the Antarctic is much colder and has a much thicker ice sheet．But the weather experts are now paying more attention to West Antarctic．It may be affected by only a few degrees of warming．

Satellite pictures show that large areas of Antarctic ice are already disappearing．The evidence available suggests that a warming has taken place．This fits the theory that carbon dioxide warms the earth．

However, most of the fuel is burnt in the northern hemisphere, where temperatures seem to be falling．Scientists conclude, therefore, that up to now natural influences on the weather have exceeded those caused by man．The question is：Which natural cause has most effect on the weather?

One possibility is ________．Astronomers at one research station have studied the hot spots and“cold”spots on the sun．As the sun rotates(旋转)，it presents hotter or“colder”faces to the earth, and different aspects to different parts of the earth．This seems to have a considerable effect on the distribution of the earth's atmospheric pressure, and consequently on wind circulation．The sun is also variable over a long term：its heat output goes up and down in cycles, the latest trend being downward．

1．What is the best title of the passage?(Please answer within 10 words．)

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2．Please fill in the blank in the last paragraph with proper words or phrases to complete the sentence．(Please answer within 10 words．)

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3．Which sentence in the passage can be replaced by the following one?

A warming on the scale from the burning of fuels may have an effect on it．

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4．Is it significant for us whether the atmosphere will be warmer or colder?Why?(Please answer within 30 words．)

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5．Translate the underlined sentence in the fourth paragraph into Chinese．

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