From DOUGLAS CROSS
Sam Freeth’s article on Lake Nyos (‘The deadly cloud hanging over Cameroon’,
15 August) provided some interesting new material on the events after the
1986 Lake Nyos explosion, but sadly posed yet more questions. The phenomenon
of inverted thermal stratification proposed by Freeth would appear to be
rather surprising to most limnologists, who have managed quite well for
many years with the more conventional phenomenon recorded in almost all
deep tropical lakes. Stratification increases, not decays as he proposes,
as the surface water of freshwater lakes warms up. My suggestion that a
seiche produced by a strong wind across the lake when it was fully saturated
could have triggered the event (Letters, New Scientist, 29 September 1988),
which now appears to have been adopted by the experts, assumed rather more
conventional lake physics, with which few limnologists would disagree.
Of rather more concern, however, is the assumption that because scientists
cannot fit the reports of people who actually experienced the event into
their theoretical model, those people must therefore be wrong, or even suffering
from ‘olfactory hallucination’. Such intellectual arrogance is the bane
of field science, as Sir Arthur Conan Doyle well appreciated almost a century
ago when he wrote, in the words of his famous scientific detective Sherlock
Holmes, ‘When you have eliminated everything which is possible then whatever
remains, however improbable, is the truth.’
Interpreting uneducated people’s conceptual frameworks often presents
formidable intellectual challenges, but in my experience that effort is
always worthwhile. If the people say that the smell and noise were simultaneous,
then it is worth taking this as the basis for a new hypothesis. For example,
some snow avalanches act as if they are aerosols travelling in low temperature
air currents, and can travel down even slight slopes at extraordinary speeds,
generating a terrifying noise as they pass. It may be that the Nyos carbon
dioxide aerosol resembled such an avalanche in the valleys below the lake.
Nor are the medical symptoms – especially of skin blistering – consistent
with partial suffocation. If the local people reported specific smells (or
tastes?) then it is worth taking a little more trouble in trying to develop
a new hypothesis about the associated chemistry, rather than simply dismissing
these reports as lacking in objectivity.
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Douglas Cross Honiton, Devon
