Dendroclimatic reconstruction of temperature in the eastern Qilian Mountains, northwestern China

Abstract

Understanding the extent to which climate has varied in the past is a prerequisite to assessing current trends. In this study, we present a 225 yr tree-ring width record of Qinghai spruce Picea crassifolia from a mesic site in the eastern Qilian Mountains of northwest China. This tree-ring record showed significant positive correlations (p <0.05) with temperature for most months from the preceding May to the current September, but none with precipitation or the Palmer Drought Severity Index. Based on the correlation relationships, we developed a regression model to reconstruct the average July temperatures over the period AD 1785-2009, which accounted for 45% of the observed temperature variation during the calibration period (1957-2009). This is the first tree-ring based temperature reconstruction in the eastern Qilian Mountains. The reconstruction indicated a warming trend that began around 1900 and continued through the late 20th century. Eight of the 10 warmest years were recorded during the period 1990-2009. The longest cool period occurred in 1894-1916. Comparisons of our reconstruction with other independent tree-ring based temperature reconstructions from the northeastern Tibetan Plateau suggest coherent variance patterns in these warm season temperature reconstructions regardless of the positive or negative correlation relationships between tree-ring records and temperatures. The results of comparisons also indicated that the warm season tem-perature variances lag behind the winter temperature variability by about 20 yr in this region.