Tree-ring-density inferred August–September temperature variability on the eastern Tibetan Plateau for the past two centuries

ABSTRACT Climate change, especially the rapid warming since the industrial revolution, has drawn much attention over the past decades. However, the short instrumental climate records on the Tibetan Plateau (TP) impede our understanding of the current status of climate. Although tree-ring-based temperature reconstructions have been developed on the TP, increasing the spatial distribution of sampling sites can improve our understanding of the recent warming. Here we present a new tree-ring maximum latewood density chronology of Balfour spruce (Picea likiangensis var. balfouriana) growing near the upper treeline on the eastern TP, and use it to reconstruct late summer (August–September) mean temperature since AD 1837. The reconstruction explains 61.7% of the actual variance of instrumental August–September mean temperature over the calibration period 1957–2014, and represents regional-scale temperature variations over the eastern and southeastern TP. The August–September mean temperature reconstruction reveals three relatively cold phases (the 1850s–1870s, the 1900s–1910s and the 1960s) and two warm periods (the 1930s–1940s and 1972–2014) over the past two centuries. Comparisons of our reconstruction with other independent tree-ring-based temperature records and glacier fluctuation documents near our research area show good consistencies in those cold and warm phases. Our reconstruction exhibits a pronounced and persistent temperature rise since the 1960s, providing a new line of evidence for the recent warming on the TP. Moreover, our results indicate that the August–September mean temperature variability over the eastern TP has a potential linkage with the EI Nino/Southern Oscillation and the Atlantic Multi-decadal Oscillation.