In the atmosphere, carbon dioxide allows the sun's rays to enter but prevents the heat from escaping. According to a weather expert's prediction, the atmosphere will be warmer in the year 2050 than it is today, if man continues to burn fuels at the present rate. If this warming took place, the ice caps in the poles would begin to melt, thus raising sea level several metres and severely flooding coastal cities. Also, the increase in atmospheric temperature would lead to great changes in the climate of the northern hemisphere.
In the past, concern about man-made warming of 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, which may be affected by only a few degrees of warming, in other words, by 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 suggests that warming has taken place. This fits the theory that carbon dioxide warms Earth.
However, most of the fuel is burnt in the northern part of Earth, 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 the most effect on the weather?
One possibility is the behaviour 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. This seems to have a greater effect on the distribution of Earth's atmospheric pressure, and consequently on wind circulation. The sun is also variable(可变的) over a long term. Its heat output goes up and down in cycles. The latest downwards trend is on the way. But that is only an imagination.
