Reconstructing historical temperature records is crucial 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, are an important natural archive for reconstructing historical temperature changes. Tree-ring blue intensity (BI), a new tree-ring indicator developed as an effective substitute of tree-ring density, has proven to be a robust proxy for reconstructing temperature variations. Nevertheless, it was unknown whether tree-ring BI could be used for climate reconstruction in the Qinling Mountains (QLM).

Tree-ring researchers of the “Extreme Climate Events and Impacts Group” (EXCEIS) from the Institute of Earth Environment, Chinese Academy of Sciences found that tree-ring BI from Pinus tabulaeformis Carr. on the southern slopes of the QLM outperforms tree-ring width (TRW) in capturing climatic signals, and the earlywood BI (EWBI) chronology exhibits the highest correlation with the maximum mean temperature from February to June (Tmax_2-6), with an r value of 0.66 (p<0.01, n=63).

Based on these findings, researchers reconstructed the history of Tmax_2-6 variations since 1847 using the EWBI chronology as a predictor. The reconstruction revealed that the QLM experienced relatively warm periods during 1871–1892, 1898–1931, and 2012–2020, and relatively cold periods during 1856–1864, 1939–1965, and 1976–1996. These warm-cold fluctuations align closely with the 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 both the Atlantic Multidecadal Oscillation (AMO) and the Pacific Decadal Oscillation (PDO) activities.

This study marks the inaugural application of the tree-ring BI indicator in dendroclimatological research of the QLM, providing a scientific basis for a deeper understanding of the region's climatic history. Furthermore, it holds significant value for climate reconstruction in regions where TRW fails to extract climatic signals.

This research published in Dendrochronologia, was jointly supported by several projects, including the Natural Science Basic Research Program of Shaanxi, the National Natural Science Foundation of China, the Strategic Priority Research Program of Chinese Academy of Sciences.