Table S1 Summary of statistics for ring-width standard chronologies of Siberian spruce and larch in the Altay Mountains

TLD / XSK / SEE / XTK / KYS / DEN / QBL / Larch (AK, KG and KN)) / RC
Chronology period / 1799–2010 / 1687–2010 / 1668–2010 / 1638–2010 / 1783–2010 / 1762–2010 / 1533–2010 / 1270–2004 / 1270–2010
The period with an EPS of at least 0.85 / 1825–2010 / 1715–2010 / 1721–2010 / 1691–2010 / 1815–2010 / 1788–2010 / 1565–2010 / 1500–2004 / 1500–2010
Mean correlation with master series / 0.74 / 0.68 / 0.58 / 0.59 / 0.74 / 0.73 / 0.60 / 0.60 / 0.58
Mean sensitivity / 0.23 / 0.21 / 0.23 / 0.18 / 0.21 / 0.27 / 0.18 / 0.22 / 0.21
Standard deviation / 0.28 / 0.30 / 0.30 / 0.22 / 0.26 / 0.32 / 0.24 / 0.30 / 0.29
First-order autocorrelation / 0.47 / 0.57 / 0.44 / 0.47 / 0.52 / 0.39 / 0.57 / 0.66 / 0.60
Signal-to-noise ratio / 39.31 / 18.55 / 15.46 / 22.19 / 25.70 / 25.49 / 13.71 / 27.01 / 33.2
Variance in first eigenvector (%) / 53.7 / 48.1 / 38.1 / 39.7 / 54.6 / 53.8 / 36.9 / 35.9 / 32.6

Table S2 Cross correlations between some ring width chronologies of spruce for the common time interval

RC / Larch / QBL / DEN / KYS / SEE / TLD / XSK
Larch / 0.60 (n=504)
QBL / 0.65 (n=445) / 0.43 (n=440)
DEN / 0.82 (n=223) / 0.12 (n=217) / 0.52 (n=222)
KYS / 0.85 (n=196) / 0.31 (n=190) / 0.45 (n=195) / 0.79 (n=196)
SEE / 0.69 (n=290) / 0.39 (n=284) / 0.51 (n=289) / 0.56 (n=223) / 0.55 (n=196)
TLD / 0.83 (n=186) / 0.35 (n=180) / 0.48 (n=185) / 0.64 (n=186) / 0.63 (n=186) / 0.62 (n=186)
XSK / 0.82 (n=296) / 0.29 (n=290) / 0.60 (n=295) / 0.69 (n=223) / 0.72 (n=196) / 0.53 (n=290) / 0.71 (n=223)
XTK / 0.76 (n=320) / 0.36 (n=314) / 0.49 (n=319) / 0.66 (n=223) / 0.73 (n=196) / 0.57 (n=290) / 0.64 (n=186) / 0.65 (n=296)

Table S3 Statistics of calibration and verification test results for the common period of 1959–2008

Calibration
(1979-2008) / Verification
(1959-1978) / Calibration
(1959-1988) / Verification
(1989-2008) / Full calibration
(1959-2008)
r / 0.650 / 0.729 / 0.782 / 0.630 / 0.696
r2 / 0.423 / 0.531 / 0.611 / 0.397 / 0.484
RE / 0.608 / 0.282
CE / 0.524 / 0.126
Sign test / 19+/1- b / 15+/5- a

a Significance at p < 0.05.

b Significance at p < 0.01.