Dendroclimatology from Regional to Continental Scales: Understanding Regional Processes to Reconstruct Large-Scale Climatic Variations Across theWestern Americas - Dendroclimatology - page 209

Fig. 7.10 Comparison of precipitation-sensitive tree-ring records across western America and El
Niño/Southern Oscillation. The reconstruction of Niño-3 region temperature (Mann et al. 2000 )
was used as a proxy for tropical forcing of precipitation variations. The series used for comparison,
from top to bottom, are: Tree-ring-based Palmer Drought Severity Index (PDSI) reconstructions
from the southwestern United States (SW US) from Cook et al. ( 2004 ) ; a composite Polylepis
record, including the Caquella and Soniquera chronologies from the Bolivian Altiplano (Argollo
et al. 2004 ) ; and the El Asiento chronology in central Chile (LeQuesne et al. 2006 ) . Correlation
coefficients between records are indicated. The number of years for the comparisons is 331. The
PDSI and the Niño-3 region reconstructions are not statistically independent. Some Texas-Mexican
chronologies were used as predictors in both reconstructions

that we are making comparisons with an annual Niño-3 index reconstruction, the
precipitation-sensitive records from the three extratropical regions in North and
South America are significantly correlated with the Niño-3 index reconstruction
during the 1650-1980 interval used for comparison (Fig. 7.10 ) . The correlation
coefficients between the PDSI reconstructions in the midwestern-southwestern
United States and the Niño-3 index oscillate between r 0.65.

Although most correlation coefficients are remarkably high, the lack of inde-
pendence between these records makes it difficult to determine the statistical
significance of these relationships.

= 0.20 and r =