Day 011 - 12 Jul 94 - Page 33
1 is all transported into the stratosphere, where it is
photodissociated to liberate two active chlorine atoms
2 which then catalytically destroy ozone. Its ODP is
therefore high. Methyl chloroform on the other hand ---"
3 We do not describe, or do we describe, that as a CFC?
A. It is not a CFC because it does not contain chlorine.
4
Q. "... On the other hand, although it contains three
5 chlorine atoms, has a much shorter lifetime since it is
destroyed chemically in the troposphere. Its ODP is
6 therefore low ---"
7 Substituting HCFC- 22 for methyl chloroform, would that
statement now correspond with what we know about HCFC- 22?
8 A. Yes.
9 Q. ".... About one- tenth of CFC- 11 Halon 1301, with a long
lifetime and one bromine atom, has a very high ODP value,
10 since a bromine atom can react with ozone a large number
of times before being converted to a more inactive
11 chemical form."
12 Then there is some material about the Montreal Protocol
and then a reference to a table showing best estimates of
13 lifetimes which is the table you drew attention to
earlier. That is at page 43, Table 4.1, where we see CFCs
14 11 and 12 mentioned with lifetimes respectively of 77 and
139 years at the top of the second column. We do see some
15 HCFCs mentioned at the bottom of the left hand column, do
we not?
16 A. Yes.
17 Q. That ought to have relatively short lifetimes- 2, 5 and 10
respectively, are they not?
18 A. Yes. HCFC- 22 is actually in the middle of that page
and that is thought to be 22 years.
19
Q. I missed that one. Well spotted- 22 years, although as we
20 saw, its estimated lifetime was later reduced to just over
fifteen. Then going back to page 46 there is a pie chart
21 which shows the attributed responsibility to these various
substances, with CFC- 12 thought to be the greatest
22 culprit by some way. Is that right?
A. It is.
23
Q. Can we move on to 1990. That is at Tab C. Here we will
24 see the executive summary on the sixth page. Again, I am
not going to read the whole of it. The first paragraph,
25
"Recent evidence from atmospheric measurements in polar
26 regions reinforces the conclusion reached in SORG 1988
that substantial damage has occurred to the ozone layer
27 due to reactive chlorine and bromine derived from man-
made CFCs and halons."
28
What are 'halons'?
29 A. Halons are the compounds which contain bromine and
their primary use is in fire extinguishers.
30
Q. Then there is some history in paragraphs 2, 3, and 4. In
