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Date:         Fri, 18 Dec 1992 09:33:36 -0400
Reply-To:     Jeremy Whitlock <WHITLOCK@SSCVAX.CIS.MCMASTER.CA>
From:         Jeremy Whitlock <WHITLOCK@SSCVAX.CIS.MCMASTER.CA>
Subject:      Re: Ozone Layer

It is clear that I am no geophysicist.  It is also clear that there is some
disagreement on the ozone-depleting potential of volcanoes and other
natural sources of stratospheric chlorine.

Jan Schloerer (schloerer@rzmain.rz.uni-ulm.de) has provided much detailed
information, for which we are grateful.  He writes:

  > From Robert Parson's article, reposted yesterday, you may recall that
  > the two most famous volcanic eruptions in the last decade coughed up
  > almost negligible amounts of Cl into the stratosphere, as determined
  > by direct measurements :
  >
  >  El Chicho'n 1982   0.04 Tg   That is, 40 000 t.  Mankin and Coffey,
  >                               Science _226_, 170, 1983
  >  [...]

Yet this reference goes on to add that 0.04 Tg is about 9% of the global
statospheric HCl burden, and to me a _single_ stratospheric injection of
this relative size is not "negligible".  Mankin and Coffey conclude with:

    "The observation that a single, large volcanic event can increase
     the stratospheric HCl burden by 40 percent over a large part of
     the globe should lead to a reassessment of the role of volcanoes
     in stratospheric chlorine chemistry."  [Mankin and Coffey, above
     reference, p.172]

I also read from Von Nostrand's Scientific Encylopaedia, p.2973, in an
article on volcanoes, that researchers have shown that the Augustine
volcano (Alaska, 1976) may have injected 289 billion kg (289 Tg) of HCl
directly into the stratosphere, which apparently is 570 times the global
industrial production of Cl and CFC's.  Given the size of this injection
(650 times the equilibrium stratospheric burden, according to the Mankin
Coffey reference above), and the presumed slow rate of transport to the
troposphere, I am not convinced that volcanoes have a negligible effect on
stratospheric ozone.

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 unprecedented danger?

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?

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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