Day 011 - 12 Jul 94 - Page 14
1 as the stratosphere.
2 Because the temperature in the stratosphere rises with
height, this means the type of convection process which
3 one can see above a convection heater, which is the
stirring of the air, is inhibited. That means in the
4 stratosphere the chemicals or the atmosphere tends to lie
in layers, whereas in the troposphere (another name is the
5 turning sphere) we have a turbulent sort of condition
which leads to rapid mixing of any chemicals which are
6 emitted.
7 The ozone is formed in the stratosphere. It is formed
because the sun emits a wide range of wave lengths; some
8 are in the region of a wave length of about 200 nanometres
which can be absorbed by molecular oxygen, or below 200
9 nanometres, and causes molecular oxygen to be broken up.
10 In the presence of third bodies, the molecular oxygen can
recombine with the atomic oxygen to form ozone. Ozone
11 itself can be broken up by light from the sun and in fact
the concentration of ozone which occurs in the
12 stratosphere is as a result of a balance between the
formation and the destruction processes.
13
That means that any chemicals which are released into the
14 atmosphere and ultimately enter the stratosphere can in
principle interrupt the process of the formation and
15 destruction of ozone.
16 Q. Pause there. If that process is interfered with or
interrupted in that way, does it matter?
17 A. Yes.
18 Q. Why?
A. If one looks at the history of our knowledge of the
19 chemical destruction processes in the stratosphere, the
first postulate that chlorine containing compounds could,
20 in principle, damage the ozone layer was made by Rowland
and Molina in 1974. Although they quite correctly, as it
21 turned out, deduced that chlorine from manmade compounds
could damage the stratosphere, the mechanism which they
22 actually suggested in 1974 has proved to be incorrect.
23 Q. I want to come back to that. What I want you to tell us
is why it matters if the ozone layer is damaged?
24 A. If the ozone layer is damaged in a region which is
inhabited, then part of the ultraviolet light which would
25 otherwise be blocked by the ozone can penetrate to the
surface of the earth. This can have several consequences;
26 the most commonly known ones are an increase in skin
irritation due to sunburn which, in principle, could lead
27 to an increase in skin cancer. There are also suggestions
in terms of agriculture that it could inhibit the
28 production of crops in certain areas, and that means that
in dry areas, where there was an increase in ultraviolet
29 light, in principle crop production could be damaged.
That would mean possibly a decrease in food production;
30 the one which is best known, however, is the skin cancer
one.
