A greenhouse is a house made of glass . It has glass walls and a glass roof . People grow vegetables , flowers and other plants in them . A greenhouse stays warm inside , even during winter . During the daylight hours , a greenhouse gets warmer and warmer and stays pretty warm at night too . This is because the heat received from the sun is trapped inside the greenhouse by the glass.

The Earth is also like a greenhouse . During the day Earth's surface warms up in the sunlight . At night , the surface cools , releasing the heat back into the air . But some of the heat is trapped by gases like carbon dioxide in the atmosphere . These gases , called greenhouse gases , work like the glass walls and the roof and keep the Earth warm . This is global warming and it is making the Earth a dangerous planet . Unfortunately , we are making the earth too hot . We are using oil , gas and coal for running cars , buses , trains , planes , power stations and so on . These fuels have carbon in them . This carbon and other gases trap the heat in the atmosphere and do not allow the earth to cool down . As a result , the Earth gets hotter.