Day 011 - 12 Jul 94 - Page 25
1 atmosphere as something like my hand, most of the blocking
----
2
Q. On that demonstration where is the earth? You have the
3 earth inside you?
A. The earth is inside me. Well, if I do it this way
4 (indicated)- if I had a finger or a thumb, this implies
that a gas is actually absorbing strongly ---- For
5 example, carbon dioxide absorbs at a wavelength of about
--- corresponding to a wavelength of about 4 micrometres.
6 So, the primary gases which cause absorption of long
wavelength radiation in the earth's atmosphere are
7 actually minor species in the earth's atmosphere compared
to nitrogen and oxygen. They are actually water and
8 carbon dioxide. That means that if one has a gas which
will absorb in what are known as the atmospheric windows,
9 which are the windows in the atmosphere where water and
carbon dioxide do not absorb, they have the potential for
10 increasing the trapping of long wavelength radiation and
hence enhancing the greenhouse effect.
11
Q. Which is the principle greenhouse gas?
12 A. Carbon dioxide.
13 Q. I am coming back to methane later on, Professor Duxbury,
but as a percentage of the total of gases which have that
14 effect, what does methane constitute?
A. About 14 per cent.
15
Q. Can we go on with this article for the moment? I have
16 finished at the parenthesis at the top of the second page-
'the greenhouse effect'. It goes on: "The company's
17 studies suggest that ozone depletion damage could increase
in proportion to the CFC molecule's chlorine weight and
18 its stability when released into the atmosphere."
19 Now, as a statement of scientific knowledge at that time,
is that correct?
20 A. Yes.
21 Q. "'Hard' CFCs such as CFC- 11 and- 12, in current use as
blowing agents, each contain more chlorine atoms than do
22 'softer' CFCs." Is that accurate?
A. It depends what you mean by 'more chlorine'. If one
23 takes HCFC- 141B that actually does contain two chlorine
atoms. On the other hand, it also contains two carbon
24 atoms. So, if one said as a percentage of the total
molecular composition it would be correct, but just to say
25 'on the number of chlorine atoms', it would not.
26 Q. Should we insert 'proportionately'?
A. 'Proportionately' would be accurate.
27
Q. "Chlorine is the ingredient scientists have linked to
28 chemical reactions said to destroy ozone. In addition,
'hard' CFCs are highly stable and therefore able to
29 survive long enough to drift up and come in contact with
the high- altitude ozone layer." So far you would not
30 disagree with that?
A. No.
