Day 011 - 12 Jul 94 - Page 21

     
     1
         Q.   What was the subject matter of the conference?
     2        A.  The subject matter of the conference was the current
              state of knowledge of the atmospheric chemistry in both
     3        the upper atmosphere, the stratosphere, and the lower
              atmosphere, the troposphere.  In fact, it was entitled
     4        Chemistry of the Interface.
 
     5   Q.   Roughly speaking, what we are discussing here?
              A.  Yes.
     6
         Q.   Can we look at the executive summary:  "Ozone in the
     7        atmosphere is important to man because it reduces the
              amount of solar ultra-violet radiation reaching the
     8        ground; this radiation has the potential to affect
              adversely the environment and human health.  The amount of
     9        UV radiation absorbed depends on the amount of ozone
              throughout the depth of the atmosphere ('column ozone').
    10        Concentrations of ozone in the atmosphere are determined
              by a complex set of processes:  the circulation of the
         atmosphere, the chemical reactions that take place in it,
              and the effects of radiation.
    12
              Statistical techniques show that there is no significant
    13        trend detectable in measurements of the global average of
              column ozone. However, there are large variations on many
    14        timescales which would make a small trend (say, less than
              1% per decade) difficult to identify.  Ozone in the upper
    15        stratosphere appears to have decreased by about 2-3% since
              1978, although measurement of this quantity is
    16        particularly error-prone".
 
    17        May I ask you this, Professor Duxbury, though again the
              answer may be obvious.  Is an estimated decrease of about
    18        two to three per cent in a period of about nine years a
              significant matter?
    19        A.  Indeed it is, because from previous records there was
              very little evidence for any decrease at all over a very
    20        long period of time.
 
    Q.   It goes on:  "Recently a large depletion, about 40%, has
              been seen in stratospheric ozone over Antarctica in the
    22        spring - the so-called 'ozone hole'.  The cause is not yet
              known".
    23        A.  That certainly was the situation at the time that this
              report was written.
    24
         Q.   August 1987?
    25        A.  Yes.
  
    26   Q.  "It may be a natural change in atmospheric circulation; it 
              may be chemical, due to increasing levels of chlorine 
    27        and/or bromine from man's activities or it may involve
              both of these.  We do not yet know if there are
    28        implications for ozone on a global scale."  Was that true
              at that date?
    29        A.  At that date that was true.
 
    30   Q.   "Large experimental campaigns mounted by the US in 1986
              and 1987 may resolve these uncertainties".  Did they