In article , Brian Sandle writes:
In sci.environment Thomas Lee Elifritz wrote:
February 2, 2004

Brian Sandle wrote:

What about the earth systems?
[...]
Lots of nice 64 bit processors starting to coming out, write yourself some
software.

My observation is that the physical scientists do not get involved in
statistics in the way social scientists do. I thought to get talking about
correlations to see what understanding could be engendered.

So what do you think of the physical scientists' amount of learning
from partial correlations?


Physical scientists, and in particlular atmospheric scientists
have learned time after time that placing
too much faith in correlations give you nasty surprises. If you just
correlate a big enough number of variables you will always get a few
good correlations just by chance. Just correlating "everything" will get you
so many hits that it is not worthwile to explore this pathway.

If you have a hypothesis that there could be a connection, as in your case
between space shuttles and ozone depletion, making a raw correlation
make some more sense. Before doing the correlation, and if not then,
certainly straight after, you should think about whether it makes any physical
sense. After all the correlation may have been a fluke, or there
may be a underlying cause to both of your variables.

As for your hypothesis, I think the latter is the case.
The increase in space shuttle flights and use of CFC and other halocarbons have
just come at more or less within the same time frame.

Now as to your physical explanations.

Part 1: Solid fuel rockets emit chlorine compunds in the stratosphere,
which depletes ozone.

True, but the problem with that argument is that this amount
is quite small compared to other emission types.

Which brings up argument 2: The emissions are relatively more important
since they happen in situ.

This argument does not hold. The chlorine emitted near the ground
are not different from the chlorine emitted from the solid fuel rockets,
so whether something is transported across the tropopause or emitted
in situ have no effect on the total ozone depletion. Thus, since the
amount of chlorine transported from below is much higher than the emissions
from the space shuttle, the contributions from the space shuttles
are small.
From http://www.business.gov/busadv/faq.cfm?catid=113

" In a 1990 report to Congress, NASA found that the chlorine released
annually in the stratosphere (assuming launches of nine Shuttle missions and
six Titan IVs--which also have solid rocket motors--per year) would be
about 0.25 percent of the total amount of halocarbons released
annually worldwide (0.725 kilotons by the Shuttle 300 kilotons from all sources)."

Not zero however and in a sci-fi scenario with tens of launches a day
it would certainly have a large effect. This scenario is however unthinkable
economically.



Øyvind Seland