IEER
SDA V6N3 / E&S #5

Science For The Critical Masses:

Lifetimes, Concentrations, and Global Warming Potential of Major Greenhouse Gases


LIFETIMES, CONCENTRATIONS, AND GLOBAL WARMING POTENTIAL OF MAJOR GREENHOUSE GASES REGULATED UNDER THE KYOTO PROTOCOL1
Global Warming Potential2
(time horizon)
Greenhouse Gas
Chemical Formula*
Atmospheric Lifetime* (years)
Pre-industrial Concentration
Concentration in 1994
Rate of concentration change3
20
yrs
100
yrs
500
yrs
carbon dioxide
CO2
50-2004
~280 ppmv
358 ppmv
1.5 ppmv/yr (0.4%/yr)
1
1
1
methane5
CH4
12±36
~700 ppbv
1720 ppbv
10 ppbv/yr (0.6%/yr)
56
21
6.5
nitrous oxide
N20
120
~275 ppbv
312 ppbv7
0.8 ppbv/yr (0.25%/yr)
280
310
170
sulfur hexafloride
SF6
3,200
0
3.2 pptv
0.2 pptv/yr (6.3%/yr)
16,300
23,900
34,900
HFC-32
CH2F2
5.6
0
0
(1989 est.)
0
2,100
650
200
HFC-125
C2HF5
32.6
0
0
(1989 est.)
0
4,600
2,800
920
HFC-134a
CH2FCF3
14.6
0
0
(1989 est.)
0
3,400
1,300
420
HFC-143a
C2H3F3
48.3
0
0
(1989 est.)
0
5,000
3,800
1,400
HFC-152a
C2H4F2
1.5
0
0
(1989 est.)
0
460
140
42
Sources:
Intergovernmental Panel on Climate Change, Climate Change 1995, (Cambridge University Press, 1996), pp. 15, 22; A. Makhijani and K. Gurney, Mending the Ozone Hole, (Cambridge, MIT Press, 1995), pp. 96, 103; M. Maiss, et al., "Sulfur Hexafluoride - a powerful new atmospheric tracer," Atmospheric Environment, Vol. 30 No. 10/11, (1996), pp. 1621-1629.

*Chemical forumlas and estimates of atmospheric lifetimes may vary. These are from IPCC, 1996.

ppbv = parts per billion by volume
ppmv = parts per million by volume pptv = parts per trillion (million million) by volume
CFC = chlorofluorocarbon
HFC = hydrofluorocarbon

Notes:
1. CFCs, HCFCs, and other halocarbons regulated under the Montreal Protocol are not included in this table.
2. Global warming potentials depend on a number of assumptions regarding the carbon cycle and CO2 concentrations. The figures given here are calculated based on the Bern carbon cycle model and current CO2 concentrations.
3. The growth rates of CO2, CH4 and N2O are averaged over the decade beginning 1984.
4. No single lifetime for CO2 can be defined because of the different rates of uptake by different sink processes.
5. The global warming potential for methane includes indirect effects of tropospheric ozone production and stratospheric water vapor production.
6. This has been defined as an adjustment time which takes into account the indirect effect of methane on its own lifetime. In other words, methane can affect the ability of the atmosphere to cleanse itself of pollutants including methane itself. See Mending the Ozone Hole, pp. 262-63 and IPCC, 1995 pp. 18-19.
7. Estimated from 1992-93 data.


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March, 1998