In addition to carbon dioxide and water vapour, there are other GHGs as well.
- Nitrous oxide (N2O)
This gas is emitted from artificial fertilizers in modern agriculture, from production of nitric acid and from combustion of fossil fuels. Nitrous oxide is responsible for approximately 4% of the anthropogenic greenhouse effect.
Nitrous oxide (N2O) in the atmosphere has increased from 270 ppb in 1750 to 314 ppb in 1998.
This is an increase by 46 ppb or 17%. The increase continues.
The present concentration of N2O has not been exceeded during at least the past thousand years.
Sources of N2O are agriculture, cattle, industry and several other natural sources. N2O is a strong greenhouse gas with a GWP of 310 times that of CO2 .
The lifetime in the atmosphere is also quite long, more than 100 years.
- Hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs).
These compounds are artificial, in the sense that they have never been in the nature before humans introduced them during the last 50 years.
HFCs are used as refrigerants in industry and e.g. in car air conditioners.
They replace to some extent the chlorofluorocarbons (CFCs) that are supposed to be phased out according to the Montreal protocol.
CFCs have an ability to deplete stratospheric ozone in the ozone layer.
Perfluorocarbons (PFCs), e.g. tetrafluoromethane (CF4) and hexafluoroethane (C2F6), are greenhouse gases with a very high global warming potential in addition to an exceptionally long atmospheric lifetime, up to thousand years.
Perfluorocarbons are primarily formed during aluminium production.
Sulphur hexafluoride (SF6) comes from the process industry, in particular from magnesium and aluminium production.