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but South Africa cool and dry. Siple, Antarctica, is a coastal location, and may
have been influenced by Antarctic coastal circulation, which is dominated by the
ocean (see Section 5.5 ). The graphs in Figure 6.9b differ considerably in detail,
reflecting regional influences.
Reviews of a range of literature by Markgraf ( 1998 ) establish a complex picture
of climate variability and change during this period in South America. Evidence
from northern Patagonia in Argentina supports the alternation of warm and cool
periods from the Peruvian ice core (Figure 6.9b ). Galapagos Island sea surface
temperatures were colder than normal between the seventeenth and nineteenth
centuries. Tree-ring evidence established that northern Patagonia temperatures
were warmer for 1080-1250, and 1720-1750, but cooler for 1270-1660. The
coldest years were 1340, and 1520-1650. Precipitation generally was lower during
warmer years, but this varied by spatial location and season. Winter precipitation
on central Chile (approximately 338 S) was highest for 1220-1280 and AD
1450-1550, and lowest for 1270-1450 and 1580-1680. Summer precipitation at
448 S in Argentina increased for 1600-1620 and 1670-1690, associated with cooler
conditions, but was lower in warmer conditions for 1720-1740 and 1770-1790.
The precipitation distribution was usually inverse between the two locations.
In Southern Africa (Lindesay 1998 ; Tyson et al. 2000 ), speleothem records
show that warmth was centered around 1500-1520, and cooler and drier condi-
tions around 1700. Figure 6.9c also shows a period of cooler climate between
600 and 800, and between 1000 and 1500. After 1000 the country became drier,
although summer rainfall in Natal increased after 1580. The Southern African
interior was up to 3 8C warmer than today during the MWP, and about 1 8C
cooler during the LIA. There is considerable spatial variability in both tempera-
ture and precipitation variations.
The hemispheres are compared by pre-1850 extremes in Table 6.2 . The original
data (Jones et al. 1998 ) contained the period after 1850, when human influences
become important, and therefore the temperature anomalies reflect differences with
a 1961-90 baseline. The warmest NH summers are grouped over a 30-year span
around 1100, reflecting the MWP. In the SH they occur between 1356 and 1469,
which in the NH was a transition period toward the LIA. The coldest summers
in the NH occurred in the seventeeth century, but also in the middle and toward
the end of the MWP. The period around 1300 must have been cold in the SH.
Decade and century results are perhaps more reflective of the generality of
the MWP and LIA descriptors. The warmest NH decade was in the middle of the
MWP, and the coldest decades in the seventeenth and nineteenth centuries.
The MWP is clearly defined as the centuries between 1000 and 1300. In the
SH, the warm centuries began and ended a little later, between 1100 and 1400.
The cold centuries extended between 1500 and 1800, but the eleventh century
was also cold in the SH, in contrast to the NH.
The results in Figure 6.9 and Table 6.2 suggest there is some evidence for both
LIA and MWP occurring in both hemispheres, but this is obscured in Figure 6.7
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