How Much are Greenhouse Gas Concentrations Changing?
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  1. Is there a seasonal variation? Is the concentration higher in summer or in winter? What biological processes might account for the seasonal differences?
  2. Is the northern hemisphere concentration the same as the southern hemisphere? Do gases with longer atmospheric lifetimes have smaller hemispheric differences?
  3. What is the concentration and how quickly is it changing?
  4. How does the concentration change during your lifetime compare with the seasonal variation?
  5. What would you predict for the concentration in 2100?
  6. Which gases should we worry about most?
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Concentration Units*
Click image for graphs
Global Warming Potential,
100-year**
Atmospheric lifetime,
years**
Carbon dioxide
CO2
link
link
ppm
link
long term
1
300-1000***
Methane
CH4
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ppb
link
long term
27.9
11.8
Nitrous oxide
N2O
link
link
ppb
link
long term
273
109
Hydrogen
H2
link
link
ppb
1-2
Carbon monoxide
CO
link
link
ppb
1.9
0.25
Trichlorofluoromethane
CCl3F
CFC-11
link
link
ppt
6,230
52
Dichlorodifluoromethane
CCl2F2
CFC-12
link
link
ppt
12,500
102
1,1,2-Trichloro-1,2,2-trifluoroethane
CCl2FCClF2
CFC-113
link
link
ppt
6,520
93
Carbon tetrachloride
CCl4
R-10
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link
ppt
2,200
32
Carbon tetrafluoride
CF4
PFC-14
link
link
ppt
7,380
50,000
Chloroform
CHCl3
R-20
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link
ppt
20.6
0.501
Chlorodifluoromethane
CHClF2
HCFC-22
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link
ppt
1,960
11.9
Fluoroform
CHF3
HFC-23
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ppt
14,600
228
Dichloromethane
CH2Cl2
R-30
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ppt
11.2
0.493
Difluoromethane
CH2F2
HFC-32
50% of R-410A
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ppt
771
5.4
Methyl chloride
CH3Cl
Chloromethane
R-40
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ppt
5.54
0.9
Methyl bromide
CH3Br
Bromomethane
link
link
ppt
2.43
0.8
1,2-Dichloro-1,1,2,2-tetrafluoroethane
CClF2CClF2
CFC-114
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ppt
9,430
189
Chloropentafluoroethane
CClF2CF3
CFC-115
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link
ppt
9,600
540
Hexafluoroethane
CF3CF3
PFC-116
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ppt
12,400
10,000
Methyl chloroform
CH3CCl3
1,1,1-Trichloroethane
R-140a
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ppt
161
5
1,1-Dichloro-1-fluoroethane
CH3CCl2F
HCFC-141b
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link
ppt
860
9.4
1-Chloro-1,1-difluoroethane
CH3CClF2
HCFC-142b
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ppt
2,300
18
1,1-Difluoroethane
CH3CHF2
HFC-152a
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link
ppt
164
1.6
1,1,1-Trifluoroethane
CH3CF3
HFC-143a
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ppt
5,810
51
1,1,1,2-Tetrafluoroethane
CH2FCF3
HFC-134a
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ppt
1,530
14
Pentafluoroethane
CHF2CF3
HFC-125
50% of R-410A
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ppt
3,740
30
Tetrachloroethene
Cl2C=CCl2
Perchloroethylene
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ppt
6.34
0.301
Propane
CH3CH2CH3
R-290
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ppt
0.02
0.036
Sulfur hexafluoride
SF6
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ppt
24,300
1,000
Less than 5 ppt
1,1,1,3,3-Pentafluoropropane
CHF2CH2CF3
HFC-245fa
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ppt
962
7.9
Bromochlorodifluoromethane
CBrClF2
Halon-1211
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ppt
1,930
16
Nitrogen trifluoride
NF3
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ppt
17,400
569
Bromotrifluoromethane
CBrF3
Halon-1301
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link
ppt
7,200
72
Chlorotrifluoromethane
CClF3
CFC-13
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link
ppt
16,200
640
Sulfur dioxide difluoride
SO2F2
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ppt
4,630
36
1,1,1,2,3,3,3-
Heptafluoropropane
CF3CFHCF3
HFC-227ea
link
link
ppt
3,600
36
Perfluorocyclobutane
C4F8
PFC-318
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ppt
10,200
3200
1,1,1,3,3-Pentafluorobutane
CF3CH2CF2CH3
HFC-365mfc
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ppt
914
8.9
Perfluoropropane
CF3CF2CF3
PFC-218
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link
ppt
9,290
2600
1,2-Dibromotetrafluoroethane
CBrF2CBrF2
Halon-2402
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ppt
2,170
28
2-Chloro-1,1,1-trifluoroethane
CH2ClCF3
HCFC-133a
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ppt
388
4.6
1,1,1,3,3,3-Hexafluoropropane
CF3CH2CF3
HFC-236fa
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ppt
8,690
213
1,2-Dichloro-1,1-difluoroethane
CH2ClCClF2
HCFC-132b
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ppt
332
3.5
1,1,1,2,2,3,4,5,5,5-Decafluoropentane
CF3CHFCHFCF2CF3
HFC-4310mee
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link
ppt
1600
17
2,3,3,3-Tetrafluoropropene
CF3CF=CH2
HFO-1234yf
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<1 ppt
(decomposes to
CF3COOH)
0.501
0.033
Trifluoromethyl
sulfur pentafluoride
CF3SF5
link
link
ppt
18,500
800
ppm = parts per million (106), ppb = parts per billion (109), ppt = parts per trillion (1012), ppq = parts per quadrillion (1015).

Infrared spectral links are to the NIST Chemistry WebBook (%T, peaks down) or the Gasmet IR Spectrum Collection (A, peaks up).

Information about Sampling Sites.

*Concentration data from the Scripps CO2 Program, the Advanced Global Atmospheric Gases Experiment (NASA), Global Greenhouse Gas Reference Network and Long-term global trends of atmospheric trace gases (Global Monitoring Laboratory, U. S. National Oceanic and Atmospheric Administration), Cape Grim Australia Greenhouse Gas Data (CSIRO), and the World Data Centre for Greenhouse Gases (Japan Meteorological Agency and the World Meteorological Organization).

**The Global Warming Potential (GWP) is used to contrast different greenhouse gases and provides a simple measure of the radiative effects of various greenhouse gases relative to CO2 defined as 1. Atmospheric lifetime is used to characterize the decay of an instanenous pulse input to the atmosphere, and represents the time the input would take to decay to 0.368 (1/e) of its original value. One hundred year time horizon GWPs and atmospheric lifetimes taken from Intergovernmental Panel on Climate Change, Climate Change 2021: The Physical Science Basis, Table 7.SM.6, p. 16-27.

***IPCC no longer lists a value for the carbon dioxide lifetime. It depends on the biosphere and concentration-dependent equilibria between the atmosphere, the ocean, and deposition of CaCO3 on timescales of a few centuries. See Annu. Rev. Earth Planet. Sci. 37:117-34 (2009) and The Atmosphere: Getting a Handle on Carbon Dioxide (NASA 2019).

Earlier versions of these pages were supported by the National Science Foundation grants DUE-9455918 and DUE-9455924.
This page created by George Lisensky, Beloit College. Last modified July 25, 2025.

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