From Open Sustainability
Carbon emissions are the release of the green house gas, carbon dioxide (CO2), into the atomoshphere. This can be due to the burning of fossil fuels for energy or through natural occurances such as volcanic eruptions.
The term is also used as a catch all for the six greenhouse gases listed in the Kyoto Protocol. The others being methane (CH4); nitrous oxide (N2O); hydrofluorocarbons (HFCs); perfluorocarbons (PFCs); and sulphur hexafluoride (SF6).
The unit of measure for Carbon emissions is metric tons of carbon dioxide (tCO2). When reporting the total emissions from all greenhouse gases the emissions are are converted into tons of carbon dioxode eqiivalent (tCO2-e) based on their global warming potential. It is used to evaluate releasing (or avoiding releasing) different greenhouse gases against a common basis.[1] An example of how organizations report carbon emissions is within British Energy's CSR Report, page 24 & 25.
Values
Carbon dioxide has a global warming potential (GWP) of exactly 1 (since it is the baseline unit to which all other greenhouse gases are compared).
| GWP values and lifetimes from 2007 IPCC AR4 [2]
| Lifetime (years)
| GWP time horizon
|
| 20 years
| 100 years
| 500 years
|
| Methane
| 12
| 72
| 25
| 7.6
|
| Nitrous oxide
| 114
| 289
| 298
| 153
|
| HFC-23]] (hydrofluorocarbon)
| 270
| 12,000
| 14,800
| 12,200
|
| HFC-134a (hydrofluorocarbon)
| 14
| 3,830
| 1,430
| 435
|
| sulfur hexafluoride
| 3,200
| 16,300
| 22,800
| 32,600
|
A GWP is not usually calculated for water vapour. Water vapour has a significant influence with regard to absorbing infrared radiation (which is the green house effect); however its concentration in the atmosphere mainly depends on air temperature. As there is no possibility to directly influence atmospheric water vapour concentration, the GWP-level for water vapour is not calculated.
References
- ↑ http://www.ghgprotocol.org/files/ghg-protocol-revised.pdf
- ↑ http://ipcc-wg1.ucar.edu/wg1/Report/AR4WG1_Print_Ch02.pdf
