Dendroclimatology from Regional to Continental Scales: Understanding Regional Processes to Reconstruct Large-Scale Climatic Variations Across theWestern Americas - Dendroclimatology - page 196

Fig. 7.9 Comparison of the amplitudes from the first principal components of the temperature
reconstructions from Patagonia ( blue line ) and the Arctic ( red line ). The Patagonian and the Arctic
records were obtained by averaging the temperature reconstructions shown in Fig. 7.8 . Common
oscillatory modes in both records have periods of ( b ) > 100 years, and ( c ) around 36 years. Time
series included in ( d ) represent the sum of the oscillations shown in ( b )and( c ) (for explanation of
the data in each panel of this figure see Fig. 7.6 )
(Fig. 7.9 ) . In both records, positive levels during twentieth-century periods exceed
values back to 1670. An abrupt decrease in temperature in both regions is recorded
in the 1810s, quite likely related to a series of large tropical volcanic eruptions,
including an unknown source in 1809, Soufriere in 1812, and Tambora in 1815,
among others (Zielinski 2000 ) . A notable feature of temperature change revealed
by the high-latitude records is the continuous transition from anomalous cold
conditions in the mid-nineteenth century to anomalous warm conditions in the
mid-twentieth century. In contrast, the global and hemispheric mean instrumental
temperatures show almost no trend between the late 1850s and the 1910s (Jones and
Moberg 2003 ) , suggesting that high latitudes in both hemispheres share common
patterns of temperature changes that are not seen at global scales.