Minimum summer temperature variations in Hanzhong, the southwestern Qinling–Bashan Mountains, China since 1879 AD

Abstract

China’s north–south climatic transitional zone, the Qinling–Bashan Mountains (QBM), is sensitive to climate change. In this paper, we present a new tree-ring width chronology derived from a Pinus henryi Mast. from the southwestern part of the QBM and demonstrate that ring width was limited by the mean summer minimum temperature between 3 May and 20 July of the previous year (r = 0.68, p < 0.001). The start and end dates of this limiting period are close to the Beginning of Summer (5–7 May) and the Greater Heat (22–24 July), respectively, of the Chinese Twenty-four Solar Terms, which are important for plant growth. We reconstructed the minimum summer temperatures in the study area since 1879 AD and found four cold periods (1879–1891, 1926–1951, 1966–1980, and 1988–1999 AD) and three warm periods (1911–1916, 1956–1962, and 2004–2010 AD). This new reconstruction not only reveals strong local climate signals but was also able to capture large-scale temperature events. The results of multi-taper spectral analysis, cross wavelet transforms, wavelet coherence analysis, and spatial correlation analysis indicate that summer temperature variations in the QBM are associated with solar activity, the El Niño-southern oscillation (ENSO), the Pacific decadal oscillation (PDO), and the Atlantic multidecadal oscillation (AMO). Our Geodetector results indicate that the combined impact of these drivers on temperature variations is much stronger than that of each individual driver, and they especially emphasize the significant impact of the interaction between the PDO and AMO on temperature variability in the study area.