Day 011 - 12 Jul 94 - Page 49
1 As the measuring techniques have improved, so as the
accuracy of the modelling because the computers have got
2 better. Perhaps I could say, my Lord, that the main model
used is actually based on the standard model used by the
3 meteorological office for weather forecasting which has
chemistry added to.
4
Q. I am not trying to attack you; I am just trying to clarify
5 things.
A. No, I am just trying to clarify the point which is
6 that the reason why it looks different from year to year
is that the measurements in the atmosphere have improved,
7 the laboratory measurements have improved and our ability
to do the calculations have improved.
8
Q. Right. But to say it is clear cut that CFCs have a long
9 life-span and HCFCs a short life-span, that is really
relative, is it not, and it could be potentially
10 misleading? Perhaps that is too strong, but what really
matters is the length of time, is their life-span?
11 A. What really matters is actually whether the thing
lives long enough to be transported to the upper
12 atmosphere, and the point about the HCFCs is that because
they will react with hydroxyl in the lower atmosphere,
13 their potential to be taken out of the system before they
every transported into the upper atmosphere where the
14 ozone is, is very much less than it is for the fully
halogenated fluorocarbons, whether they be carbon
15 tetrachloride or, in fact, CFC-12, CFC-11.
16 Q. Could we go back to your statement?
A. Yes.
17
Q. On page 5, where you are talking about short term
18 releases, where you say: "Short term releases of a more
highly reactive compound such as HCFC-22 can put a large
19 transient burden on the atmosphere", what do you mean by
that?
20 A. I mean basically (and this is actually paraphrasing
what the SORG report says), that if you have even a more
21 reactive compound which gets into the atmosphere, it can
actually increase the chlorine loading. If it is
22 transient because the average lifetime is much shorter
than the fully halogenated species, then the chlorine
23 loading will be of a shorter duration.
24 Q. But?
A. The point I was trying to make is that the ozone
25 depleting potential does make an estimate of how certain
reactions occur. The chlorine loading is just based on
26 the fact you are actually adding a compound to the
atmosphere containing chlorine.
27
Q. In the short term then could this actually have a more
28 severe effect?
A. If you read the SORG report, you will see that the
29 only reason this came in was that it was actually a group
of scientists pointing out that, in fact, the HCFCs could
30 increase the amount of chlorine in the atmosphere.
Therefore, although at present they were classed not as,
