VIEWS: 60 PAGES: 8 POSTED ON: 6/4/2010
GROUP A (APRIL) Greenhouse Effect and Global Warming The Earth is wrapped in a blanket of air called the 'atmosphere', which is made up of several layers of gases. The sun is much hotter than the Earth and it gives off rays of heat (radiation) that travel through the atmosphere and reach the Earth. The rays of the sun warm the Earth, and heat from the Earth then travels back into the atmosphere. The gases in the atmosphere prevent some of the heat from escaping into space. These gases are called greenhouse gases and the natural process between the sun, the atmosphere and the Earth is called the 'Greenhouse Effect', because it works the same way as a greenhouse. The windows of a greenhouse play the same role as the gases in the atmosphere, keeping some of the heat inside the greenhouse. THE NATURAL GREENHOUSE EFFECT We know that the atmosphere has a number of gases, often in tiny amounts, which trap the heat given out by the Earth. To make sure that the Earth's temperature remains constant, the balance of these gases in the atmosphere must not be upset. 1 The GREENHOUSE GASES are very important and are mainly: Water vapour- occurs naturally in the atmosphere. Carbon dioxide- produced naturally when people and animals breathe. Plants and trees absorb carbon dioxide to live. Volcanoes also produce this gas. Methane- comes from cattle as they digest their food. The gas also comes from fields where rice is grown in paddy fields. Nitrous oxide- when plants die and rot, nitrous oxide is produced. Ozone- occurs naturally in the atmosphere. THE GREENHOUSE EFFECT CAUSED BY MAN Some of the activities of human also produce greenhouse gases. These gases keep increasing in the atmosphere. Burning fossil fuels such as coal, oil and natural gas releases carbon dioxide into the atmosphere. Cutting down and burning trees also produces a lot of carbon dioxide to the environment. A group of greenhouse gases called the chlorofluorocarbons (CFCs) have been used in aerosols, such as hairspray cans, fridges and in making foam plastics. They are found in small amounts in the atmosphere. They are dangerous greenhouse gases because a small amount of it can trap large amounts of heat. Because there are more and more greenhouse gases in the atmosphere, more heat is trapped which makes the Earth warmer. This is known as GLOBAL WARMING. A lot of scientists agree that man's activities are making the natural greenhouse effect stronger. If we carry on polluting the atmosphere with greenhouse gases, it will have very dangerous effects on the Earth. THE EFFECTS With more heat trapped on Earth, the planet will become warmer, which means the weather all over Earth will change. For example, summers will get hotter, and winters too. This may seem a good idea, but the conditions we are 2 living in are perfect for life, and a large rise in temperature could be terrible for us and for any other living thing on Earth. The Weather In future, the winter and summer temperatures will increase and the weather will be warmer. In winter it may also rain more but in summer it may become drier. In other parts of the world, the effects will be different, some places will become drier and others will be wetter. Although most areas will be warmer, some areas will become cooler. There may be many storms, floods and drought, but we do not know which areas of the world will be affected. All over the world, these weather changes will affect the kind of crop that can be grown. Plants, animals and even people may find it difficult to survive in different conditions. Sea Levels Higher temperatures will make the water of the seas and oceans expand. Ice melting in the Antarctic and Greenland will flow into the sea. All over the world, sea levels may rise, perhaps by as much as 20 to 40 cm, by the beginning of the next century. Higher sea levels will threaten the low-lying coastal areas of the world, such as the Netherlands, Bangladesh and low lying parts of India. Throughout the world, millions of people and areas of land will be at danger from flooding. Many people will have to leave their homes and large areas of farmland will be ruined because of floods. Farming The changes in the weather will affect the types of crops grown in different parts of the world. Some crops, such as wheat and rice grow better in higher temperatures, but other plants, such as maize and sugarcane do not. Changes in the amount of rainfall will also affect how many plants grow. The effect of a change in the weather on plant growth may lead to some countries not having enough food and many people could suffer from hunger. 3 Water Everywhere in the world, there is a big demand for water and in many regions, such as the Sahara desert in Africa and Thar desert in India; there is not enough water for the people. Changes in the weather will bring more rain in some countries, but others will have less rain. IN DANGER! Plants & Animals It has taken million of years for life to become used to the conditions on Earth. As weather and temperature changes, the homes of plants and animals will be affected all over the world. For example, polar bears and seals will have to find new land for hunting and living, if the ice in the Arctic melts. Many animals and plants may not be able to cope with these changes and could die. This could cause the loss of some animal and plant species in certain areas of the world or everywhere on Earth resulting to the decline of Natural Resources. People The changes in climate will affect everyone, but some populations will be at greater risk. For example, countries whose coastal regions have a large population, such as Egypt and China, may see whole populations move inland to avoid flood risk areas. The effect on people will depend on how well we can adapt to the changes and how much we can do to reduce climate change in the world. 4 OZONE HOLE We have already discussed in the beginning that the atmosphere is made up of several layers. About 19-30 kilometers above the Earth is a layer of gas called ozone, which is a form of oxygen. Ozone is produced naturally in the atmosphere. WHY DO WE HAVE AN OZONE LAYER? The ozone layer is very important because it stops many of the sun's 'ultra-violet rays' (UV rays) getting through to the Earth - these are the rays that cause our skin to tan. Too much UV can cause skin cancer and will also harm all plants and animals. Life on Earth could not exist without the protective shield of the ozone layer. WHAT IS THE OZONE HOLE? Every spring, a hole as big as the USA develops in the ozone layer over Antarctica, in the South Pole. A smaller hole develops each year over the Arctic, at the North Pole. And there are signs that the ozone layer is getting thinner all over the planet. The loss of the ozone layer occurs when more ozone is being destroyed by human activities than nature is creating. WHAT CAUSES THE OZONE HOLE? One group of gases is particularly likely to damage the ozone layer. These gases are called CFCs, Chloro-Fluoro-Carbons. CFCs are used in some spray cans to force the contents out of the can. They are also used in refrigerators, air conditioning systems and some fire extinguishers. They are used because they are not poisonous and do not catch fire. Most countries have now stopped using new CFCs that can be released into the atmosphere, but many scientists believe that we must stop using old ones as well. 5 THE OZONE HOLE AND OUR HEALTH The ozone layer is like a sunscreen, and a thinning of it would mean that more ultra-violet rays would be reaching us. Too many UV rays would cause more sunburn, and because sunburn causes skin cancer, this too would increase deaths. These UV rays are also dangerous for our eyes and could cause an increase in people becoming blind. That is why sun cream and sunglasses are very important. THE OZONE HOLE ON ANIMALS AND PLANTS UV rays can go through water and end up killing small water animals or plants, called 'plankton' which form the base of the food chain in oceans and seas. Whales and other fishes have plankton as their main food, and if plankton dies because of these UV rays, whales will start dying too, because they will not have anything to eat. Large amounts of UV rays could damage all green plants. If the ozone layer keeps getting thinner, there could be fewer and fewer plants on Earth, and then there would be less food in the whole world. THE TWO-FACED OZONE GAS Ozone found between 19 and 30 kilometers high in the atmosphere is one of the reasons why we are alive on Earth. But when the gas ozone is found lower down where we can breathe it in, it becomes very dangerous for our health. This ozone is caused by a reaction between air pollution and sunlight and can cause modern-day smog. This is different to the smog that formed in the early 20th century from smoke and fog. 6 Our Responsibilities What can you do: There are many things we can do to help reduce air pollution and global warming. Use buses and trains instead of cars, as they can carry a lot more people in one journey. This cut down the amount of pollution produced and also saves the fuel. Walking or cycling whenever you can, will be better as it does not create any pollution. It will also be good for your body, as regular exercise will keep you fit and healthy. If your parents use the car, ask them to avoid using it for very short journeys if possible, as this creates unnecessary pollution. Try to encourage them to share their journeys with other people, for example when they go to work or go shopping. Also encourage them to drive more slowly as this produces less pollution and less carbon dioxide. Energy is produced to generate electricity and to keep us warm. Most energy is produced by the burning of fossil fuels, like coal, oil and gas, which release carbon dioxide, a greenhouse gas. Fuel burnt in our cars also releases carbon dioxide. As an individual, you do not have a lot of control on how your energy is produced. However, you can control the way in which you use that energy. Using less energy means less of it needs to be produced. So less carbon dioxide is released into the atmosphere. We can also help prevent pollution from our own homes which may contribute to acid rain and poor air quality, and increases emissions of carbon dioxide in the atmosphere. Turning off lights when they are not needed and not wasting electricity will reduce the demand for energy. Less electricity will 7 need to be produced and so less coal, oil and gas will have to be burnt in power stations, which means less air pollution and less carbon dioxide! Pollution formed indoors can be reduced by ensuring that all gas appliances are working correctly. Good ventilation will improve indoor air quality by dispersing biological pollutants like dust mite, and other pollutants such as cigarette smoke. Most of the rubbish we throw away can be recycled, such as glass bottles and jars, steel and aluminium cans, plastic bottles and waste paper. Recycling used materials uses less energy than making new ones. Composting fruit and vegetable waste reduces the amount of rubbish buried at rubbish dumps. What are the Governments doing? Governments throughout the world have already taken action for these different environmental problems (i.e. Acid Rain, Air Quality, Ozone Hole, and Global Warming). In their plans they hope to reduce the amount of emissions of greenhouse gases produced by man. About half of the greenhouse effect is caused by our use of energy, especially from fossil fuels. Other sources of energy could be used which do not emit carbon dioxide, e.g. wind power, solar (sun power) and wave power. In the home and at school, we must learn to use energy efficiently and not waste it. Although adults do many things to help stop global warming, kids can do just as much. Kids can’t do hard things like making a law, but we can do easier things like not watching as much TV. You can listen to your parents when they say, turn off your lights or go play outside. Listening to them and actually trying to help can help you, your environment, and the world. 8
"Greenhouse Effect and Global Warming - DOC"