How Much are Ozone Depleting 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 to see graph)
Ozone Depleting Potential**
Atmospheric lifetime (years)**
Carbon dioxide
CO2
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ppm
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long term
0
100
Methane
CH4
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ppb
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long term
0
12.4
Nitrous oxide
N2O
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ppb
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long term
0.017
121
Ozone
O3
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ppb
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Total column (Dobson)
hours-days
Hydrogen
H2
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ppb
0
1-2
Carbon monoxide
CO
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ppb
0
0.25
Trichlorofluoromethane
CCl3F
CFC-11
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ppt
1
45.0
Dichlorodifluoromethane
CCl2F2
CFC-12
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ppt
0.82
100.0
Trichlorotrifluoroethane
CCl2FCClF2
CFC-113
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ppt
0.85
85.0
Carbon tetrachloride
CCl4
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ppt
0.82
26.0
Chloroform
CHCl3
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ppt
0.01
0.40
Dichloromethane
CH2Cl2
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ppt
0.004
0.4
Difluoromethane
CH2F2
HFC-32
Component (50%) of R-410A
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ppt
0
5.2
Methyl chloride
CH3Cl
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ppt
0.02
1.0
Tetrachloroethene
Cl2C=CCl2
Perchloroethylene (perc)
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ppt
0.007
0.25
Methyl chloroform
CH3CCl3
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ppt
0.16
5.0
Chlorodifluoromethane
CHClF2
HCFC-22
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ppt
0.04
11.9
Chlorodifluoroethane
CH3CClF2
HCFC-142b
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ppt
0.06
17.2
Dichlorofluoroethane
CH3CFCl2
HCFC-141b
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ppt
0.12
9.2
Difluoroethane
CH3CHF2
HFC-152a
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ppt
0
1.5
Tetrafluoroethane
CH2FCF3
HFC-134a
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ppt
0
13.4
1,1,1-Trifluoroethane
CH3CF3
HFC-143a
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ppt
0
47.1
Pentafluoroethane
CHF2CF3
HFC-125
Component (50%) of R-410A
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ppt
0
28.2
2,3,3,3-Tetrafluoropropene
CF3CF=CH2
HFO-1234yf
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?
0
0.029
1,1,1,3,3-Pentafluorobutane
CF3CH2CF2CH3
HFC-365mfc
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ppt
0
8.7
Fluoroform
CHF3
HFC-23
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ppt
0
222
Perfluoroethane
CF3CF3
PFC-116
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~ 4 ppt
0
10,000
Bromochlorodifluoromethane
CBrClF2
Halon-1211
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ppt
7.9
16
Methylbromide
CH3Br
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ppt
0.66
0.8
Dibromotetrafluoroethane
CBrF2CBrF2
Halon-2402
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ppt
13.0
20
Bromotrifluoromethane
CBrF3
Halon-1301
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ppt
15.9
65
Sulfur hexafluoride
SF6
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ppt
0
3,200
Trifluoromethyl sulfur pentafluoride
CF3SF5
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ppt
0
800
Nitrogen trifluoride
NF3
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ppt
0
500
Carbon tetrafluoride
CF4
PFC-14
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~80 ppt
0
50,000
ppm = parts per million (106), ppb = parts per billion (109), ppt = parts per trillion (1012).

*Concentration data from the Scripps CO2 Program, the Carbon Dioxide Information Analysis Center (U. S. Department of Energy), Global Greenhouse Gas Reference Network (U. S. National Oceanic and Atmospheric Administration), and the World Data Centre for Greenhouse Gases (Japan Meteorological Agency).

**The Ozone Depletion Potential (ODP) is used to contrast different gases and provides a simple measure of the expected impact on ozone per unit mass emission of a gas relative to that caused by CFC-11 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. Atmospheric lifetimes taken from Intergovernmental Panel on Climate Change, Climate Change 2013: The Physical Science Basis, Table 5.1, p. 731-738. ODP values from World Meteorological Organization, Scientific Assessment of Ozone Depletion: 2010, Table 5.1 and United Nations Environment Programme, New Ozone-Depleting Substances, May 2012.

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 September 6, 2015.

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