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Date:         Mon, 21 Dec 1992 11:43:46 -0400
Reply-To:     Jeremy Whitlock <WHITLOCK@SSCVAX.CIS.MCMASTER.CA>
From:         Jeremy Whitlock <WHITLOCK@SSCVAX.CIS.MCMASTER.CA>
Subject:      Re: Ozone Layer

 Robert Parson (PARSON_R@cubldr.colorado.edu) writes:

 >> Question:  I've read that ozone variation with latitude and season
 >> are on the same order as that defining the ozone "hole".  How does
 >> this affect the belief that the ozone "hole" presents an unprece-
 >> dented danger ?
 >
 >You need to take the baseline into account. At the equator, the ozone
 >layer is about 260 DU thick, almost independent of season. Over central
 >Europe it ranges from ~275 to ~360 DU. Over the arctic you get huge swings,
 >from ~275 to ~475 DU, since the seasonal variation of sunlight is so large.
 >Notice that the _minimum_ ozone value is about the same.
 >But nowhere on earth outside the antarctic do you get the behavior seen
 >in the ozone hole: starting from a normally low winter value of ~300 DU,
 >the ozone concentration plummets in early spring, hitting a monthly average
 >of ~150 DU in October with daily lows going as far down as 108 DU.

I disagree that the baseline is as important as the relative change.  It
may be a fact of nature that the ozone layer is thinner over the antarctic,
and indeed polar plantlife is adapted to a higher UV-B flux.  The relative
change, which is what will affect lifeforms, is on the same order as
relative changes with latitude and season elsewhere on the globe.


>> Question:  What is the scientific consensus regarding man-made
>> ozone depletion?  If the "hole" was discovered the same year they
>> started making observations, and has fluctuated since then, what kind
>> of cause-and-effect relationships can we have observed ?
>
> Jan already answered most of this, I'll take another tack. The most
> convincing evidence that the hole is due to ClO was obtained by Anderson
> et al. in the fall of 1987 (unfortunately several of the best general
> references, such as Stolarski's Jan '88 Sci. American article, were written
> before this and thus are out of date.) They found that the ClO and
> ozone concentrations are beautifully anticorrelated, even down to local
> fluctuations - as ClO goes up, Ozone goes down.

This tells me that ClO and ozone concentrations are anticorrelated.  I'd
still like to know if cause-and-effect has been demonstrated for man-made
sources.

> These are the results that made
> DuPont (who sent their own atmospheric scientist along on the mission)
> agree to phase out CFC's.

Since DuPont stands to make a huge profit from its non-CFC refrigerants,
etc., I would hesitate to place any significance on their show of concern.


Jan Schloerer <schloerer@RZMAIN.RZ.UNI-ULM.DE> writes:

>The story that the ozone hole was already in place in 1956 is entirely
>erroneous. It has a complicated history itself, in which the University
>of Virginia Professor Fred Singer plays a major role.  Robert Parson
>unearthed this in a (long !) post to sci.env on 9 May 1992 which I can
>repost if so desired.

I would appreciate this, perhaps by personal e-mail.

Jeremy.
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Jeremy Whitlock                        e-mail:  WHITLOCK@MCMASTER.CA
Dept. of Engineering Physics
McMaster University                    phone: (416) 525-9140 ext.7140
Hamilton, Ont.
CANADA   L8S 4L8
                   "My thoughts are mine, not Mac's"
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