Carbon in the Atmosphere

Reservoir Times

The impact of greenhouse gases on the enhanced greenhouse effect is determined by their residence time in the atmosphere.

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Atmospheric residence time represents the average amount of time the molecules of a greenhouse gas exist in air before it is removed or converted to something else. When atmospheric residence time is greater, the total impact of a greenhouse gas on global warming is larger.

The average residence time of atmospheric gases are:
	1) water vapor (H₂O) 9 days
	2) carbon dioxide(CO₂) tens of thousands of years
	3) methane (CH₄) 12 ±3 years
	4) chlorofluorocarbons (CFC) decade to century

Consequently, anthropogenic greenhouse gases will impact global warming long after emission cut-backs are achieved.