Epilogue - Natural Hazards - page 290

matched during the Mediaeval Warm Period (centered
on the thirteenth century), there is no match in the
geological record to the current rapid increase in
Greenhouse gases. Thus, the climatic consequences
of increased Greenhouse gases are speculative and
uncertain.

criticized. Yet, frequencies equating with the return
period of sunspots appear in enough climatic and
geophysical data that solar geomagnetic cycles cannot
be ignored as a precursor for natural hazard events.
Similarly, the correlation of rainfall and drought cycles
with the 18.6-year lunar cycle should not be ignored.
The coincidence of drought, across most of the grain
producing regions of the world, with the M N lunar
tidal component now demands that this cycle be taken
seriously.
Secondly, the occurrence of natural hazards is
increasing in frequency: if not in terms of the number
of events, then in terms of economic cost. The Munich
Reinsurance Company, especially since 1960, can sub-
stantiate this trend through payout claims. This point is
well-illustrated for volcanic activity this century. After
the Caribbean eruptions of 1902, volcanism leading to
large death tolls virtually ceased for half-a-century. A
similar quiescence is evident in climatic records. The
1930s and 1940s were exceedingly passive as far as
storm events were concerned. Air temperatures
globally tended to be warm, and weather patterns did
not fluctuate strongly. This does not imply that there
were no climatic disasters. After all, this period
witnessed the dust bowl years on the Great Plains of
the United States, and Hitler's armies experienced a
Russian winter that was only matched in severity by
that which afflicted Napoleon in 1812. Beginning
about 1948, climate globally began to become more
extreme. This variability has increased substantially
since 1970. For example, since 1980 Australia has with-
stood two of the largest regional flood events on record
- sandwiched between three of the largest 1 in
200 year droughts recorded. In the United Kingdom,
in the late 1980s, temperatures seasonally tended to
oscillate from the coldest to the warmest on record.
This enhanced variability is prominent in both climatic
and geological phenomena. In terms of natural hazard
events, we presently live in a period that may be
experiencing a shift in hazard regime.
Thirdly, natural hazards are pervasive in time and
space. A simple plot of the location of the hazards
mentioned in this topic will illustrate this fact.
Normally, we do not expect droughts to strike England,
tornadoes to sweep through Edmonton, Canada, or
snow to fall in Los Angeles. However, such events have
happened in the latter half of the twentieth century.
Part of the reason so-called unusual events are occur-
ring in places where they are not expected may lie in

MODERN CONSEQUENCES OF
NATURAL HAZARDS

This topic has been concerned with natural hazards
that are within the present realm of possibility: that
we have lived with, will continue to experience, and
hopefully can survive. The basic purpose of the text is
to present the reader with a clear description of
the mechanisms producing climatic and geological
hazards. An attempt has been made to enliven that
presentation with historical descriptions and support-
ive diagrams. There are four themes that are indirectly
addressed throughout the text. It is worthwhile here
briefly summarizing these.
Firstly, natural hazards are predictable. This is
especially applicable to climatic hazards. With satellite
monitoring, short-range computer forecasting models
and the wealth of experience of trained personnel and
scientists, most climatically hazardous events can be
forecast early enough to give the general population
time to respond to any threat. Whether or not these
warnings are believed is most relevant in today's world.
The fact that the British Meteorological Office ignored
an extra-tropical storm warning issued by their
counterparts in France; that residents in Darwin were
more interested in partying for Christmas when
Cyclone Tracy was barreling down on them; or that the
duty officers in Sydney ignored their own amateur
storm-watch observers as the worst hailstorm on
record overtook the city, does not negate the fact that
most climatically hazardous events are being pre-
dicted. It only illustrates that a society, its organized
bureaucracy, or its individuals have a major influence
in determining how effectively warnings of, and
preparations for, a natural disaster are accepted.
Also pointed out in this text is the fact that the
degree of prediction is strongly influenced by regular
astronomical cycles, such as the 11- and 22-year
sunspot and the 18.6-year lunar cycles. Sunspot
numbers have tended to obscure the more significant
prognostic variable, namely solar geomagnetic activity.
These avenues of forecasting have been strongly