Greenhouse gases are components of the atmosphere that absorb outgoing heat (infrared radiation) from the earth surface causing some heat to be retained. This acts as a natural blanket over the earths surface making it warm and able to sustain life as we know it. Without this greenhouse effect, the earth would be on average 20-30C colder.

However, it is now almost universally agreed that human activity has led to a dramatic increase in greenhouse gases in our atmosphere which in turn is causing more heat to be trapped in our atmosphere causing global warming.

A basket of six human induced greenhouse gases have been identified under the Kyoto Protocol as requiring reductions in emissions. These are:

	Carbon Dioxide	CO2
	Methane	CH4
	Nitrous Oxide	N2O
	Hydroflurocarbons	HFCs
	Perfluorocarbons	PFCs
	Sulphur Hexafluoride	SF6