As a crucial component of China’s north–south climatic transitional zone, the Qinling–Bashan Mountains (QBM) are characterized by high biodiversity as well as high ecological vulnerability. Research on historical climate change in this area holds significant implications for evaluating and forecasting the impacts of climate change, enhancing ecological protection and promoting regional sustainable development.

Tree-ring researchers of the “Extreme Climate Event and Impacts Group” (EXCEIS) from the Institute of Earth Environment, Chinese Academy of Sciences (IEECAS) found that the radial growth of Pinus henryi Mast. in the Hanzhong region of Shaanxi Province was limited by the mean summer minimum temperature between 3 May and 20 July of the previous year (T_min-summer, r = 0.68, p < 0.001). Interestingly, 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) of the Chinese Twenty-four Solar Terms, respectively, indicating the significance of temperature variations during specific solar term periods on tree growth.

Based on above findings, the team reconstructed the T_min-summer history since 1879 AD (accounting for 45.65% of the variance), which revealed 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), with 2004–2010 AD being the warmest period. The new reconstruction not only showed strong local climate signals in the QBM, but also captured large-scale temperature events, e.g., the warming trend in eastern China since the 1970s.

Factors such as solar activity, El Niño-Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO) and Atlantic Multidecadal Oscillation (AMO) had significant influence on T_min-summer variations, and the combined impact of these factors on T_min-summer was much stronger than that of each individual factor. It particularly highlighted the combined impact of PDO and AMO (+AMO/-PDO) on T_min-summer.

The study was published in Dendrochronologia on Feb. 10.

Contact: BAI Jie, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an, China. Email: baijie@ieecas.cn