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Figure 6.8 Tree-ring
reconstructions of summer
temperatures in Tasmania
(
8
C) and two locations in
Argentina (anomalies from
the average,
8
C). (Diaz
and Bradley
1995
: with
permission from National
Academies Press)
of the MWP, which is not reflected in the SH data. The LIA between 1550
and 1850 is strongly indicated in the NH data, but only weakly in the SH
series (see detailed discussion in Section
6.4.3
). The overall difference
between the pre-1900 maximum and minimum components of the curves is
less than 1.5 8C.
One major problem with the SH composite result is that, individually, the data
sets that comprise average patterns such as in Figure
6.7
do not show much
similarity (Diaz and Bradley
1995
). This situation is illustrated in Figure
6.8
,
which contrasts tree-ring reconstructions in Tasmania and Argentina. The
detailed variations show little agreement, even in the two Argentinean records,
and there are no apparent trends. Similar disagreements occur between records
for New Zealand (Williams et al.
1999
). This problem emphasizes that care
needs to be taken in interpreting multi-proxy records, and that regional effects
and large low-frequency variance can interfere with obtaining representative
results on a hemispheric scale.
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