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 expels are Bow paying more attention to West Antarctic，which may be affected by only a few degrees of warming，in other words，by a warming on the scale that will possibly take place in the next fifty

　　years from the burning of fuels．

　　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 gone beyond those caused by man．The question is：Which natural cause．has most effect on the weather?

　　One possibility is the variable behavior of the sun．Astronomers at one research station have studied the hot spots and‘cold’spots(that is，the relatively less hot spots)on the sun．As the sun rotates(旋转)，every 27．5 days，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 changeable over a long term：its heat output goes up and down in cycles，the latest trend being downward．

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