Re: Statistics 101

["Jerry Cohen" <jjcohen@PRODIGY.NET>]

Ruth,

    I learned in Statistics 101 that while correlation can provide a 

basis for suspicion, it does not prove a cause and effect relationship.

Again I ask, how do you know that if we had not stopped using freon,

the depletion rate wouldn't have slowed anyway?

----- Original Message -----

From: RuthWeiner@aol.com

To: jjcohen@prodigy.net

Sent: Wednesday, July 25, 2001 8:00 PM

Subject: Re: A response to Jerry Cohen's reasonable request

In a message dated 7/25/01 6:33:42 PM Mountain Daylight Time,
jjcohen@PRODIGY.NET writes:

He went so far as to complain that the Swedish
> Academy had political motives for awarding the Nobel Prize for Chemistry
> to Rowland, Molina, and Crutzen for their work on ozone depletion.  He
> has apparently since been persuaded to abandon the more extreme aspects
> of that position, but still argues that non-ozone-hole ozone depletion
> has turned around at 4% depletion.  He does not credit the Montreal
> agreement for that turn around.<

   How can you be sure that the turn-around in ozone deletion would not
have
occurred even without changes in CFC policies? From what I have seen, the

Rowland and Molina richly deserved that prize (I simply don't know Crutzen's
work, but I do know Rowland's and Molina's).  The ozone/CFC question differs
considerably from the "greenhouse" cliamte change question.  In 1979 or 1979,
McElroy and colleagues published a paper in SCIENCE correlating depletion of
the ozone layer with worldwide production and use of Freon aerosol sprays.  
It was a beautiful, unmistakeable positive correlation.  When we stopped
using Freon aerosols, the rate of depletion slowed.  Freon aerosols put
orders of magnitude more CFCs in the air, especially CF3Cl, than auto air
conditioning systems, refrigerators, or any other closed but leaky system,
and I think in controlling those we have gone overboard.

Rowland and Molina's elucidation of the mechanism for ozone depletion is
classic work.  I use this example in our textbook, in fact, to pooint out the
difference between the ozone depletion story and the greenhouse gas story.

Ruth Weiner, Ph. D.
ruthweiner@aol.com