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Scientists say the temperature of the earth could rise by 3°C over the next 50 years. This may cause drought in some parts of the world, and floods in others, as ice at the North and South Poles begins to melt and sea levels rise.
Global warming is caused by the greenhouse effect. Normally, heat from the sun warms the earth and then escapes back into space. But carbon dioxide and other gases in the atmosphere trap the sun's heat, and this is slowly making the earth warmer.
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Most of the energy we use today comes from coal, oil and gas. But these will not last forever, and burning them is slowly harming the atmosphere. We need to look for other ways of supplying energy.
Solar power is a way of using the sun's energy as heat or to make electricity. We can also use wind-power by building modern windmills that spin in the wind. There are several types of water-power: river water in mountainous areas can be used to generate hydroelectric power, and we can also create electricity from sea water flowing in and out with the tides.
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Factories, power stations and motor vehicles pump large quantities of carbon dioxide and other waste gases into the air. This is a major cause of the greenhouse effect. A lot of petrol contains lead, which is very poisonous and can cause brain damage in children. Many people now prefer to use unleaded petrol.
Some poisonous gases dissolve in water in the atmosphere and then fall to the earth as acid rain. Acid rain damages trees and buildings, and can kill fish in lakes and rivers. Rivers can also be polluted by industrial waste from factories and chemical fertilizers and pesticides used by farmers.
Recycling is the processing of used objects and materials so that they can be used again. About 60% of rubbish from homes and factories contain materials that could be recycled. Recycling saves energy and raw materials, and also reduces damage to the countryside.
Glass, paper and aluminium cans can all be recycled very easily. Many towns have bottle banks and can banks where people can leave their empty bottles and cans for recycling. A lot of paper bags, writing paper and greetings cards are now produced using recycled paper.
Rainforests help to control global warming because they absorb carbon dioxide. In recent years, large areas have been destroyed, as the trees are cut down for wood or burned to clear the land for farming. The burning releases large amounts of carbon dioxide into the atmosphere.
Many rainforests grow on poor soils, and when they are cut down or burned, the soil is washed away in the tropical rains, so that the area may turn to desert. Many plant and animal species that live there could become extinct.
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The ozone layer is a layer of gas high above the surface of the earth that helps to protect it from the sun's ultraviolet radiation, which can damage our skins and cause cancer. Scientists have recently discovered holes in the ozone layer, caused by substances called CFCs (chlorofluorocarbons).
CFCs are used in refrigerators, aerosol cans and in the manufacture of some plastic products. Some companies now make aerosols that do not contain CFCs, and these are often marked 'ozone-friendly'.
