Extreme Weather, Climate and Natural Disasters in Ireland

Extreme Weather, Climate and Natural Disasters in Ireland
seven major texts from 431 ad to 1649 ad. 5 The thick
line is the 10-year moving average: each text ends on
a different year and final pages are often lost to decay
or interference, whilst in other cases scattered entries
have been added through time. Though many entries
are duplicated between the texts, each provides different
densities of coverage in entries per year. The mean
value for Fig. 2.1 is 29.5 entries per year (median 27,
standard deviation 18.9). Because the available entries
are not distributed through time evenly, the mean,
median and standard deviation are unrepresentative for
many periods. It is tempting to interpret the variation in
Fig. 2.1 as reflecting the level of recording undertaken
through time, with marked trends corresponding to
known phases of Irish history (e.g. low but increasing
numbers from 431 ad might represent the progressive
establishment of Christianity and the spread of literacy
among monasteries). This is, however, speculative
as the seven texts from which the data is drawn have
often abbreviated (or incorporated already abbreviated
versions of) earlier texts, while material in unknown
texts may not be incorporated in the surviving Annals.
Because duplicates are not removed, a proportion of
5 (i) Annals of the Four Masters; (ii) Annals of Ulster; (iii)
Annals of Inisfallen; (iv) Carew Fragment; (v) Annals
of Tigernach; (vi) Annals of Loch Ce; (vii) Annals of
Connaught.
the variation in Fig. 2.1 is controlled by the number of
texts providing coverage for given periods rather than
the absolute number of records surviving for those
periods.
2.2 Chronologies of Extremes from the
Annals
It is possible to obtain chronologies of the combined
records of extremes of wind, precipitation and
temperature from the Annals. As noted above, these are
derived from the seven major texts. Relevant records
have been taken from the respective texts from about
431 ad to the date of their cessation around 1600.
The differing meteorological origin and spatial extent
of certain extremes also necessitates the exclusion of
some records to allow a comparison of like with like
(e.g. in the frequency of extremes per 50-year period).
This means that the derived chronologies are likely to
describe trends in events or episodes across Ireland
rather than local events, for example in Munster. It is
acknowledged that even large-scale synoptic systems
(e.g. storms) may have a variable impact across
relatively small geographical areas. This is highlighted
by major storms such as the great 1703 ad storm that
severely affected England (Wheeler, 2003) being felt
only moderately in Ireland, while the ‘night of the big
Figure 2.1. Combined available yearly records.
Time: 431-1649 AD
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