From: ae277@yfn.ysu.edu (Stewart Rowe)
Subject: Re: Question on CFC ban
Organization: Youngstown State University/Youngstown Free-Net
Date: Sat, 29 Aug 1992 01:20:42 GMT


Suggest you follow the advice of "edean" in the following:
 
 
 
  If anyone wants proof that ozone depletion
is occurring in temperate latitudes, I suggest they check out the 4-17-92
issue of _Science_ which documents just such depletion over parts of the
U.S. from space, airborne _and_ ground measurements.
 
If someone wants to see what the scientific opinion is about volcanic
cause of ozone depletion, I suggest volume 334 of the journal _Nature_.
I'll give you a hint, it isn't significant.
 
If anyone would like a list of scientific references dealing with ozone
depletion, I will gladly e-mail them to you.
 
From: dean@vexcel.com (Dean Myerson)
 
Then, for more information, read on (another forwarded post):
 
 
Topic 157        Debunking Ozone debunkers        Response  2 of  2
larris
en.climate        12:01 pm  Aug  2, 1992
 
My apologies for not responding sooner - it took me some time to
find this material in my files!!
 
I have attached here a posting from sci.environment which was
made in response to a similar question in the past.  The first
addresses your question number 1 quite completely, I think.  If
you have questions about it, best to write to author directly -
parson_r@cubldr.colorado.edu
 
On question number 2, I quote from an article on page 17 of the July
1992 issue of Physics Today:
 
"The AASE researchers wondered if the aerosols from Mt. Pinatubo
might have a significant impact on the chemical composition of the
atmosphere.  But no evidence of a substantial impact in the Arctic
region was found.  While the scientists believe that reactions on liquid
aerosols such as those composing the Pinatubo cloud are important,
conversion of inorganic chlorine to ClO [the "bad" chlorine molecule]
in polar stratospheric clouds is substantially faster.  Air moving
through warm air laden with Mount Pinatubo aerosols was hardly perturbed
chemically, whereas air only briefly exposed to polar stratospheric
clouds exhibited large depletions in ClONO2 and HCl."
 
and later in that article, discussing depletion of NOx and hence
higher observed levels of ClO...
 
"The aerosol burden of the atmosphere was of course greatly increased
this year by the Mt. Pinatubo output, which may have enhanced the
surface area of atmospheric particulates by a factor of 20 to 30 at
mid-latitudes.  However, because the background [present prior to
eruption] aerosols might have already converted most of the NOx, the
additional aerosols from Mt. Pinatubo may not have had a proportional
effect, at least at high latitudes and altitudes below 20 km."
 
You can find the gory details of the AASE expedition in the topic
"NASA Arctic Ozone Press Release" posted 5/13/92 in this conference;
it is quite long and very detailed.  For a good overview of the
ozone depletion issue and the basic chemistry - check the conference
gan.air.climate.
 
As for your question #3 - this is the first I had heard of this
particular 1960's phenomena.  However, if weather conditions were
right, this could indeed be possible - see the recent topic in
this conference "Ozone Question for BC" for a discussion of how
weather patterns can affect total column ozone.
 
I hope this helps - let us know if you have other questions...
 
Lelani
 
--------------------------------------------------------------------
 
Topic 134        Myth of the "1956 Ozone Hole"
parson_r        sci.environment         3:42 pm  May  9, 1992
(at cubldr.colorado.edu)        (From News system)
 
 
     There is a story going around, to the effect that an Antarctic
Ozone Hole was seen in the years 1956-58.  If this were true it would
strongly suggest that the Hole is a natural phenomenon having little or
nothing to do with the emission of chlorofluorocarbons (CFC's), since
very few were being produced back then.  More generally, it would be
strong evidence against any connection between the Hole and the very
high springtime concentrations of chlorine-containing free radicals (eg.
ClO) in the Antarctic stratosphere, since the total amount of chlorine
in the stratosphere in 1958 was only about 25% of what it is today. 
This is very perplexing since the evidence for this connection is
extremely strong; airborne measurements in 1987 showed a near-perfect
anticorrelation between ClO and ozone concentrations as a function of
latitude and time. [J. G. Anderson, D. W. Toohey, and W. H. Brune, "Free
Radicals within the Antarctic Vortex: the Role of CFC's in Antarctic
Ozone Loss". _Science_ _251_, 39 (4 Jan. 1991).]
     Well, the story is false. It is not, I am sure, a deliberate distortion;
I suspect it is rather the result of some careless literature work and of
quotations reproduced out of context. The ozone layer in 1956-58 was perfectly 
normal.
     Reference to a 1956 ozone hole first appeared in an article by
University of Virginia Professor S. Fred Singer in _National Review_, 30
June 1989. Professor Singer is one of the few atmospheric
scientists who is not convinced that the increase in CFC's is the
principal cause of the ozone hole. (He does not, however, dispute the
ClO-ozone connection, and he agrees that the increase in Cl is
"probably" due to CFC's. [S. Fred Singer, "Stratospheric Ozone: Science
and Policy", in _Global Climate Change_, ed. by S. Fred Singer, Paragon
House, NY 1989].)
I quote from p. 37 of the _National Review_ article:
 
" In reaction to my suggestion published in _EOS_, Professor Marcel
  Nicolet, a distinguished Belgian atmospheric physicist, has reminded us 
  in a note to the same journal of a long-forgotten publication by G. M.
  B. Dobson, the Oxford professor who started modern ozone observations. 
  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 per cent] lower than
     expected... In November the ozone values suddenly jumped up to those
     expected... It was not until a year later, when the same type of annual
     variation was repeated, that we realized that the early results were
     indeed correct and that Halley Bay showed a most interesting difference
     from other parts of the world.' "
 
(Bracketed insertions [] are Singer's. _EOS_ contains the transactions
of the American Geophysical Union.  A "Dobson Unit" is
a measure of the total amount of ozone in a column overhead; 
1 DU = 1 milliatmosphere-cm = 2.69E16 molecules/cm**2.)
 
     The story has most recently appeared in an article by Ronald Bailey
in the June 1992 issue of _Reason_ magazine. Quoting from p. 29:
 
  "The University of Virginia's Singer points out that G.M.B. Dobson, the
   inventor of the machine that measures ozone, reported very low ozone
   values - only 150 Dobson units - over Halley Bay in 1956 and 1957."
 
While Singer quotes a _reduction_ of 150 DU rather than a measured value
of that magnitude, his parenthetical [50%] seems to imply that he takes 300 DU
to be the 'expected' value, which is consistent with what Bailey says.
 
     At this point we need to review the _normal_ behavior of the ozone
layer. It is thinnest at the equator, about 265 DU (monthly average),
hardly changing at all with the seasons. In contrast it is much thicker
in the arctic and shows a prononounced seasonal trend, varying smoothly
between ~275-300 DU in autumn and ~450 DU in spring. The antarctic ozone
layer behaves somewhat differently because the very cold air mass is
effectively isolated from the rest of the stratosphere. Under normal
(pre-~1982) conditions, antarctic ozone concentrations increase very
slowly during the early spring (the photochemical production of ozone
from oxygen is rather slow), then suddenly shoot up in November when the
polar vortex breaks up and warm, ozone-rich air rushes in from lower
latitutes.
     The seasonal behavior inside the ozone hole is entirely different.
In early spring the ozone concentration begins to _drop_ rapidly from
its already normally low (~300 DU) values, hitting ~150 DU in mid-
October. This persists until the vortex breaks, after which ozone levels
return to normal. Note that the minimum coincides with Singer's and
Bailey's interpretation of Dobson's quote.
 
[Background references:
 F. Sherwood Rowland, "Stratospheric Ozone Depletion", in
 _Ann. Rev. Phys. Chem._ _42_, 731-768 (1991).
 Richard P. Wayne, "Chemistry of Atmospheres", 2nd ed., Oxford 1991.]
 
     I looked up the quotation from Dobson as reported by Nicolet (it's
actually part of an Editor's Note, _EOS_ _70_, 130 (1989); it's a
somewhat longer extract than that given by Singer), and from there got
the original reference: G.M.B. Dobson, _Applied Optics_ _7_, 387 (1968).
His Fig. 16 (p. 401) shows his results from Halley Bay for the years 1956-
58. It does not show anything like 150 DU (in fact the vertical axis goes from
200-500 DU). Instead it shows a level of ~275-300 DU for
winter and early spring, followed by a rapid rise to ~400 DU in
November: precisely the _normal_ behavior described above.
     So what's the meaning of Dobson's remarks? Here's the full text,
from p. 403 of his paper (the quotation in _EOS_ is essentially the same):
 
     "One of the more interesting results on atmospheric ozone which
came out of the IGY [International Geophysical Year] was the discovery
of the peculiar annual variation of ozone at Halley Bay (Fig. 16). This
particular ozone instrument had been to Shotover to be checked up
immediately before leaving England.  Moreover, Evans, who took the
original observations at Halley Bay, had also been to Shotover to become
familiar with the working of the instrument and its maintenance. The
annual variation of ozone at Spitzbergen was fairly well known at the
time, so, assuming a six months' difference, we knew what to expect.
However, when the monthly telegrams from Halley Bay began to arrive and
were plotted alongside the Spitzbergen curve, the values for September
and October 1956 were about 150 units lower than was expected. We
naturally thought that Evans had made some large mistake or that, in
spite of checking just before leaving England, the instrument had
developed some fault. In November the ozone values suddenly jumped up to
those expected from the Spitzbergen results.  It was not until a year
later, when the same type of annual variation was repeated, that we
realized that the early results were indeed correct and that Halley Bay
showed most interesting difference from other parts of the world. It is
clear that the winter vortex over the South Pole was maintained late
into the spring and that this kept the ozone values low.  When it
suddenly broke up in November both the ozone values and the stratosphere
temperatures suddenly rose."
 
 Taking this together with the results in the figure, we see that Dobson
and his team discovered the normal behavior of Antarctic ozone, not an
ozone hole. The "150 units lower than expected" means 150 units lower
than the results normally found in the arctic in the corresponding
season, i.e. 300 DU instead of 450. So much for the "1956 ozone hole".
 
 
 
Forwarded by
 -Stewart Rowe usr2210a@tso.uc.edu  srowe@igc.org
Newsgroups: sci.environment