a greenhouse building made of glass which for keeping plants outside temperature is low. In a similar way there are several gases in the atmosphere which trap the heat produced by the sun and prevent it'from escaping. These gases are known as"greenhouse gases", and the way in which they trap heat in the "greenhouse efïect". This is not simlpy air pollu tion. Without most of the main greenhouse gases existing nainually in the atmt»sphere it would be 30 degrees colder and human life would not exist. In other words, th greenhouse efïect is a natural course, which is to some degree helpful to us. The problem is that in the last century and a half, we have been putting too many of these gases into the earth's atmosphere by btu-ning large quantities of coal and oil. Greenhouse gases are making the world warmer. The world's temperature has already gone up by half a degree this century, and the sea level has risen by 10 centimetres. If the amount of carbon dioxide in the atmosphere doubles, there will probably be a rise in the earth's temperature of between 1 and 4 ℃. This may seem a small increase, but it woitld be enough to cause major changes in geography and agriculture. Large areas of the world would be flooded and some areas would become dry unable to produce crops It is important, too. To consider that there may be a delay of. About 30 years in the geenhouse effect This means that we are probably experiencing only the effect of. The gases put into the atmosphere before the 1980s. Since then, our of these gases has greatly increased.

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