a green house is a building made of glass which is used for keeping plants warm when the 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 atmosphere is called the " greenhouse effect". This is not simply air pollution. Most of the main greenhouse gases exist naturally in small amounts in our atmosphere, and without them the earth would be 30 degrees colder and human life would not exist . In other words, the greenhouse effect is a natural course, which is to some degree helpful to us. 5 "Greenhouse Effect" means---------