The first temperature reconstruction based on tree-ring blue intensity in the Qinling Mountains

Reconstructing historical temperatures is crucial for understanding climate history and predicting future changes. While traditional proxies such as tree-ring width, stable isotopes, and X-ray density, may be limited by poor temperature signal capture or high costs, the emerging blue intensity (BI) in tree rings provides an effective alternative for low-latitude temperature reconstruction. Here for the first time, we introduce BI to examine the climatic signals in Pinus tabulaeformis Carr. from the Qinling Mountains (QLM). We develop chronologies for tree-ring width (TRW), earlywood BI (EWBI), latewood BI (LWBI), and Delta BI (DeltaBI) based on P. tabulaeformis samples, and then successfully reconstruct the mean February–June maximum temperature (Tmax_2–6) anomalies over the past 174 years using the EWBI chronology, with an explained variance of 43.56 % for the observed data. Our key findings include: 1) Tree-ring BI data in the QLM retains stronger climatic information than the TRW data. 2) Our reconstruction reveals that QLM experienced three significant warm periods (1871–1892, 1898–1931, and 2012–2020) and three cold periods (1856–1864, 1939–1965, and 1976–1996). The new reconstruction aligns with nearby temperature reconstructions and climate grid data, documenting similar temperature fluctuations in the western Loess Plateau and the QLM. 3) It suggests a significant link between Tmax_2–6 variations in the QLM and large-scale climate oscillations, specifically the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO). This study affirms the utility of tree-ring BI for climate research in the QLM, offering insights that benefit similar low-latitude areas.