Global Warming - What Causes the Greenhouse Effect?

The Earth is kept warm by it's atmosphere, . Heat from the sun passes through the atmosphere, warming it up, and most of it warms the surface of the planet. As the Earth warms up, it emits heat in the form of infra-red radiation - much like a hot pan emits heat even after it's taken away from the cooker. Some of this heat is trapped by the atmosphere, but the rest escapes into space. The "greenhouse gases" make the atmosphere trap more of this radiation, so it gradually warms up more than it should, like a greenhouse (although a greenhouse actually does this by stopping warm air rising and escaping from it).

What Causes The Greenhouse Effect?

There are some natural greenhouse gases: water vapour, nitrous oxide, carbon dioxide, methane and ozone. However, over the past fifty years, production of carbon dioxide, nitrous oxide and methane has risen sharply, and a new type of chemical - the chlorofluorocarbon, or CFC - has been introduced as a refrigerant, solvent and aerosol propellant, but it is also a very powerful greenhouse gas, because it can trap a lot of radiation - one molecule of CFC is 12,000