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
link
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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
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link
ppt
6,520
93
Carbon tetrachloride
CCl4
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ppt
2,200
32
Chloroform
CHCl3
link
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ppt
20.6
0.501
Dichloromethane
CH2Cl2
link
link
ppt
11.2
0.493
Difluoromethane
CH2F2
HFC-32
50% of R-410A
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ppt
771
5.4
Methyl chloride
CH3Cl
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ppt
5.54
0.9
Tetrachloroethene
Cl2C=CCl2
Perchloroethylene
link
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ppt
6.34
0.301
Methyl chloroform
CH3CCl3
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link
ppt
161
5
Chlorodifluoromethane
CHClF2
HCFC-22
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link
ppt
1,960
11.9
1-Chloro-1,1-difluoroethane
CH3CClF2
HCFC-142b
link
link
ppt
2.300
18
1,1-Dichloro-1-fluoroethane
CH3CFCl2
HCFC-141b
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ppt
860
9.4
1,1-Difluoroethane
CH3CHF2
HFC-152a
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ppt
164
1.6
1,1,1,2-Tetrafluoroethane
CH2FCF3
HFC-134a
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ppt
1,530
14
1,1,1-Trifluoroethane
CH3CF3
HFC-143a
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ppt
5,810
51
Pentafluoroethane
CHF2CF3
HFC-125
50% of R-410A
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link
ppt
3,740
30
2,3,3,3-Tetrafluoropropene
CF3CF=CH2
HFO-1234yf
link

<1 ppt
(decomposes to
CF3COOH)
0.501
0.033
Propane
CH3CH2CH3
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ppt
0.02
0.036
1,1,1,2,3,3,3-
Heptafluoropropane
CF3CFHCF3
HFC-227ea
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ppt
3,600
36
Perfluoropropane
CF3CF2CF3
PFC-218
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ppt
9,290
2600
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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link
ppt
914
8.9
Fluoroform
CHF3
HFC-23
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ppt
14,600
228
Perfluoroethane
CF3CF3
PFC-116
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ppt
12,400
10,000
Bromochlorodifluoromethane
CBrClF2
Halon-1211
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ppt
1,930
16
Methylbromide
CH3Br
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ppt
2.43
0.8
1,2-Dibromotetrafluoroethane
CBrF2CBrF2
Halon-2402
link
link
ppt
2,170
28
Bromotrifluoromethane
CBrF3
Halon-1301
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link
ppt
7,200
72
Sulfur hexafluoride
SF6
link
link
ppt
24,300
1,000
Trifluoromethyl
sulfur pentafluoride

CF3SF5
link
link
ppt
18,500
800
Nitrogen trifluoride
NF3
link
link
ppt
17,400
569
Carbon tetrafluoride
CF4
PFC-14
link
link
ppt
7,380
50,000
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 and the MIT Center for Global Change Science), 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 August 12, 2024.

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