Tree-ring based summer minimum temperature reconstruction for the southern edge of the Qinghai-Tibetan Plateau, China

Information about historical summer temperature variability is rare on the Qinghai-Tibetan Plateau (QTP). Here we report a 290 yr summer (June to August) mean minimum temperature (SMMT) record reconstructed from tree-ring widths of alpine juniper Sabina squamata in Yadong County at the southern edge of QTP, China. The reconstruction accounts for 51.2% of the SMMT variance in the instrumental period from 1956 to 2002. Five cold intervals in 1725-1734, 1745-1789, 1817-1825, 1860-1869 and 1967-1978, and 4 warm intervals in 17351744, 1790-1816, 1870-1879 and 1990-2002 were identified. Wavelet analysis of the reconstructed temperatures suggested the existence of 2 to 7 yr cycles in discontinuous periods and 20 to 25 yr cycles in the 1850s to 1880s. The reconstructed summer temperature variations were consistent with other temperature records from tree rings, ice cores and glacier activities on the QTP, which demonstrate the fidelity of the reconstruction and suggested that the climate in the study region was part of a large-scale climate system. The 1980s to 2000s were the warmest period in the last 3 centuries in our tree-ring records, but the amplitude of the warming was still within the natural variation.