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The "greenhouse effect" may be making the earth warmer. What is the greenhouse effect?
It is very warm inside a greenhouse. Sunlight pours in through the glass walls and roof and warms up the inside of the greenhouse. The glass walls don't let the heat out. When this type of thing happens to the earth, it is called the greenhouse effect, and it may be changing the earth's climate.
The greenhouse effect is caused by an increase of carbon dioxide, methane, and other gases, including chlorofluorocarbons (CFCs) in the air. These gases trap the sun's heat close to the earth. Carbon dioxide and other gases come from the fossil fuels we burn. Methane comes from rice fields, decaying plants and rotting waste in landfills. CFCs are chemicals that were used in spray cans. They are still used as coolants in refrigerators and air conditioners.
We add to the problem when we cut down trees in tropical rainforests and clear land for roads and buildings. The trees release carbon dioxide after they are cut and when they decay or burn. If we didn't cut down trees they would use some of the carbon dioxide we are making. Trees and green plants use carbon dioxide during photosynthesis. This is the process where trees and green plants take up carbon dioxide and give off oxygen. Humans and other animals need oxygen to live.
Some scientists say the earth's temperature has already gone up 1 degree F because of the greenhouse effect. This may not sound like much, but by the middle of the next century it may be up by two to five degrees. A two- to five-degree increase could melt the polar ice caps. There would be more water in the oceans if the ice caps melted. If there was more water in the oceans, some coastlines would be under water. A warmer planet could upset the balance among plants, animals and weather.
Swiss, M., Air Pollution, Air & Waste Management Assoc., 1991.