Impacts On The Overall Greenhouse Effect
The contribution of each gas to the greenhouse effect is affected by the characteristics of that gas, its abundance, and any indirect effects it may cause. For example, the direct radiative effect of a mass of methane is about 72 times stronger than the same mass of carbon dioxide over a 20-year time frame but it is present in much smaller concentrations so that its total direct radiative effect is smaller, in part due to its shorter atmospheric lifetime. On the other hand, in addition to its direct radiative impact, methane has a large, indirect radiative effect because it contributes to ozone formation. Shindell et al. (2005) argue that the contribution to climate change from methane is at least double previous estimates as a result of this effect.
When ranked by their direct contribution to the greenhouse effect, the most important are:
Compound |
Formula |
Contribution (%) |
---|---|---|
Water vapor and clouds | H 2O |
36 – 72% |
Carbon dioxide | CO2 | 9 – 26% |
Methane | CH 4 |
4 – 9% |
Ozone | O 3 |
3 – 7% |
In addition to the main greenhouse gases listed above, other greenhouse gases include sulfur hexafluoride, hydrofluorocarbons and perfluorocarbons (see IPCC list of greenhouse gases). Some greenhouse gases are not often listed. For example, nitrogen trifluoride has a high global warming potential (GWP) but is only present in very small quantities.
Read more about this topic: Greenhouse Gas
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