Values
Carbon dioxide has a 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 p212 (2001 IPCC TAR in parentheses) |
Lifetime (years) | GWP time horizon | ||
|---|---|---|---|---|
|
|
|
|
||
| Methane | 12 (12) | 72 (62) | 25 (23) | 7.6 (7) |
| Nitrous oxide | 114 (114) | 289 (275) | 298 (296) | 153 (156) |
| HFC-23 (hydrofluorocarbon) | 270 (260) | 12,000 (9400) | 14,800 (12,000) | 12,200 (10,000) |
| HFC-134a (hydrofluorocarbon) | 14 (13.8) | 3,830 (3,300) | 1,430 (1,300) | 435 (400) |
| Sulfur hexafluoride | 3200 (3,200) | 16,300 (15,100) | 22,800 (22,200) | 32,600 (32,400) |
Although water vapour has a significant influence with regard to absorbing infrared radiation (which is the green house effect; see greenhouse gas), its GWP is not calculated. Its concentration in the atmosphere mainly depends on air temperature. There is no possibility to directly influence atmospheric water vapour concentration.
The values given in the table assume the same mass of compound is released. This must not be confused with chemical reactions in which masses change from reactants to products. For instance, burning methane to carbon dioxide would indeed reduce the global warming impact, but by a smaller factor than the one given in the table because the mass of methane burning is lesser than the mass of carbon dioxide released (ratio 1:2.75). If you started with 1 tonne of methane which has a GWP of 25, after combustion you have 2.75 tonnes of CO2, each tonne of which has a GWP of 1. The effect of this burning is to reduce the Global warming effect of the gas released in the ratio 25:2.75 or by about 9.
Read more about this topic: Global-warming Potential
Famous quotes containing the word values:
“Culture is the name for what people are interested in, their thoughts, their models, the books they read and the speeches they hear, their table-talk, gossip, controversies, historical sense and scientific training, the values they appreciate, the quality of life they admire. All communities have a culture. It is the climate of their civilization.”
—Walter Lippmann (1889–1974)
“With the breakdown of the traditional institutions which convey values, more of the burdens and responsibility for transmitting values fall upon parental shoulders, and it is getting harder all the time both to embody the virtues we hope to teach our children and to find for ourselves the ideals and values that will give our own lives purpose and direction.”
—Neil Kurshan (20th century)
“Our culture is ill-equipped to assert the bourgeois values which would be the salvation of the under-class, because we have lost those values ourselves.”
—Norman Podhoretz (b. 1930)