Reconstructing historical temperature records is essential for understanding the evolution of climate history, assessing current climatic conditions, and predicting future climate changes. Tree rings, with their precise annual dating and high resolution, serve as important natural archives for reconstructing historical temperature changes. Tree-ring blue intensity (BI), a new indicator developed as an effective substitute for tree-ring density, has proven to be a robust proxy for temperature variations. However, it was previously unknown whether tree-ring BI could be utilized for climate reconstruction in the Qinling Mountains (QLM).

To tackle this issue, researchers from the Institute of Earth Environment of the Chinese Academy of Sciences discovered that tree-ring BI from Pinus tabulaeformis Carr. on the southern slopes of the QLM outperforms tree-ring width (TRW) in capturing climatic signals. The earlywood BI (EWBI) chronology shows the highest correlation with the maximum mean temperature from February to June (Tmax_2-6), with a correlation coefficient (r value) of 0.66 (p<0.01, n=63).

Based on these findings, the researchers reconstructed the history of Tmax_2-6 variations since 1847, using the EWBI chronology as a predictor. The reconstruction indicated that the QLM experienced relatively warm periods during 1871–1892, 1898–1931, and 2012–2020, and relatively cold periods from 1856–1864, 1939–1965, and 1976–1996. These fluctuations between warm and cold periods closely align with temperature variations across most of the QLM and the western Loess Plateau.

Further analysis suggests a significant correlation between Tmax_2-6 changes in the QLM and the activities of both the Atlantic Multidecadal Oscillation (AMO) and the Pacific Decadal Oscillation (PDO).

This study marks the first application of the tree-ring BI indicator in dendroclimatological research in the QLM, providing a scientific basis for a deeper understanding of the region's climatic history. Moreover, it holds significant value for climate reconstruction in areas where TRW is unable to effectively capture climatic signals.

The findings were published in Dendrochronologia and received joint support from the Natural Science Basic Research Program of Shaanxi, the National Natural Science Foundation of China, and other sources.