Emissions of Greenhouse Gases in the United States 1997 - Table 1. Global Atmospheric Centrations of Selected Greenhouse Gases

Table 1. Global Atmospheric Concentrations of Selected Greenhouse Gases

Item	Carbon Dioxide	Methane	Nitrous Oxide	Sulfur Hexafluoride	Perfluoromethane
Item	(parts per million)			(parts per trillion)
Preindustrial Atmospheric Concentration	278	0.700	0.275	0	0
1992 Atmospheric Concentration	356	1.714	0.311	32	70
Average Annual Change, Recent Years	1.6	0.008	0.0008	0.2	1.2

Average Percent Change, Recent Years	0.4	0.6	0.25	0.6	1.7
Atmospheric Lifetime (Years)	50-200	12	120	3,200	50,000
Source: Intergovernmental Panel on Climate Change, Climate Change 1995: The Science of Climate Change (Cambridge, UK: Cambridge University Press, 1996), pp. 92-93.