The incredible shrinking hole

In Eco-Scam (page 135) Ronald Bailey writes that "University of Virginia environmental scientist Fred Singer points out that Sir G. M. B. Dobson, the inventor of the machine that measures ozone, reported very low ozone values-only 150 Dobson units-over Halley Bay, Antarctica, in 1956 and 1957.  (By contrast, in the 1960s and 1970s, the level was over 300 Dobson units.)" But this is just plain wrong, no value under 300 Dobson units was reported at Halley Bay in the 1950s, and Bailey should have known that (values going back to the earliest measurements can be found in Farman et al and in the ozone FAQ).  To try to determine the source of the error, I turned to the article by Singer that Bailey cited.

Singer's article "My Adventures in the Ozone Layer" was originally published in National Review (June 30, 1989) and has been widely cited in the brownlash literature.  Singer (page 542) wrote that "Dobson recounts that when the Halley Bay Antarctic station was first set up in 1956, the monthly telegrams showed that 'the values in september and October 1956 were about 150 [Dobson] units [50 percent] lower than expected."  If true, this would mean that Dobson did report levels of 150 units, but as noted above this was not the case.  (Dobson (page 403) did not give any percent difference in the amount of ozone.)   Singer's mistake was apparently in using the wrong formula.

The correct formula is:

amount of difference/amount expected * 100%

using approximate numbers this gives 150 units/ 450 units *100% = 33.3%

The formula that Singer apparently used (based on an example of a similar type of problem reported in Dewdney (page 5)) is:

amount of difference/amount actually found * 100%

again using approximate numbers this gives 150 units/300 units * 100% = 50%

Note that if the numbers were reversed (the difference was 300 units and the amount found was150 units) this leads to a lowering of over 100%, an impossible situation.

300units/150units * 100% = 200%

The 1% solution

In The Holes in the Ozone Scare, the major source on ozone depletion used by Dixy Lee Ray in Environmental Overkill, Rogelio Maduro and Ralf Schauerhammer argue that natural sources of chlorine are much greater than CFCs.  (This argument has been widely debunked, see for example Taubes and the ozone FAQ.)  They try to bolster their argument with some math abuse that lowers the amount of chlorine released by the breakup of CFCs by a factor of 100.  They use an annual production of 1.1 million tons of CFCs, containing approximately 750,000 tons of chlorine (page 11).  On page 12 they state that "According to the theory, approximately only 1 percent of the CFCs produced on Earth is broken up in the stratosphere every year. . . . Therefore, a year's production of CFCs would contribute at most 7,500 tons of chlorine to the atmosphere."

But this is wrong.  What is broken up each year (assuming a 100 year atmospheric life span) is not 1 % of that year's production, but 1 % of the CFCs in the atmosphere.  The amount in the atmosphere would be the amount released that year, plus the 99 % of the CFCs present in the atmosphere from the year before that was not broken up.  To illustrate this, I will use a purely hypothetical situation.  It assumes a yearly production of 750,000 tons of CFCs (as chlorine), that all of the CFCs produced are released into the atmosphere and that there is no delay in the mixing of CFCs in the atmosphere.  (In reality, when the problem with CFCs was discovered usage was increasing rapidly, some of the CFCs produced are not released until years later and there is an initial delay while the CFCs drift through the lower atmosphere.)

Atmospheric CFC chlorine budget (theoretical)
In thousands of tons

  Year  

 Amount in atmosphere   Amount released by photodecomposition

1

750

7.5

2

1493

15

3

2228

22

4

2955

30

5

3676

37

10

7171

72

20

13657

137

30

19522

195

40

24827

248

50

29625

296

Only in the first year is 7500 tons of chlorine released, after that the amount increases rapidly. This chart points out one of the problems when persistent chemicals are released into the environment, the amount present increases rapidly, and within a few years greatly exceeds the annual production.  And if production is halted, the chemical persists in the environment for years. This can be seen in a second chart, which assumes that after 50 years of use the production of CFCs is abruptly halted.

Atmospheric CFC chlorine budget (theoretical)
In thousands of tons

  Year  

 Amount in atmosphere Amount released by photodecomposition

1

29625

296

2

29382

293

3

29035

290

4

28745

287

5

28457

284

10

27063

270

20

24474

245

30

22135

221

40

20018

200

50

18104

181

Update

Maureen Christie (pages 188 to 190) used a similar analysis to reach the same conclusion, Maduro and Schauerhammer greatly underestimated the amount of chlorine added to the stratosphere from the breakup of CFCs.  Her husband John, taking into account the increasing use of CFCs and other sinks for them estimated that the actual release was about 30%.

References

Bailey, Ronald, Eco-Scam:  The False Prophets of Ecological Apocalypse, St. Martin's Press, 1993

Christie, Maureen, The Ozone Layer:  A Philosophy of Science Perspective, Cambridge University Press, 2000

Dewdney, A. K., 200% of Nothing:  An Eye-Opening Tour through the Twists and Turns of Math Abuse and Innumeracy, John Wiley & Sons, Inc. 1993.

Dobson, G. M. B., "Forty Years Research on Atmospheric Ozone at Oxford University:  A History", Applied Optics, Vol. 7, No. 3, 1968, pp 387-405.

Farman, et al., "Large Losses of Total Ozone in Antarctica Reveal Seasonal ClOx/NOx Interaction", Nature, May 16, 1985, pp 207-210.

Maduro, Rogelio A. and Ralf Schauerhammer, The Holes in the Ozone Scare:  The Scientific Evidence That he Sky Isn't Falling, 21st Century Science Associates, 1992.

Ray, D and L. Guzzo, Environmental Overkill:  Whatever Happened to Common Sense?, HarperCollins, 1993.

Singer, S. Fred, "My Adventures in the Ozone Layer", pp 535-545 in Jay H. Lehr, Ed., Rational Readings on Environmental Concerns, Van Nostrand Reinhold, 1992.

Taubes, Gary, "The Ozone Backlash", Science, June 11, 1993, pp 1580-1583.

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Written by Jim Norton

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