Reconstructed temperature change in late summer over the eastern Tibetan Plateau since 1867 CE and the role of anthropogenic forcing

Anthropogenic influence on the temperature change in the Tibetan Plateau (TP) since the 19th century has been rarely studied. Here we investigate the temperature change in late summer (August-September) over the eastern TP since 1867 based on a new tree-ring reconstruction. Human influence on the temperature change is explored using an optimal fingerprinting method and the model experiments from Coupled Model Intercomparison Project Phase 5 and 6 (CMIP5 and CMIP6). We find that there is a long-term warming trend since 1867 in the eastern TP based on the temperature reconstruction of a new tree-ring mean latewood density chronology. The reconstructed temperature explains 54.8% of the variance in observed August-September mean temperature during the calibration period 1961-2009, and shows decadal to inter-decadal variation. Compared with other reconstructed temperature series and observed gridded data, the temperature reconstruction shows similar increasing trend with most of temperature series. The new generation of climate models, including CMIP5 and CMIP6, are able to reproduce the long-term warming of the temperature, indicating a good performance of the climate models in simulating the temperature change in the eastern TP since the mid-19th century. The attribution analysis about the role of anthropogenic forcing shows that the signal of human influence can be clearly found in the long-term temperature change in the region. Anthropogenic signal can be detected in both the single- and two-signal analyses in all the investigated time periods, while the influence from natural forcing appears negligible.

Automated summary

The study indicates a long-term warming trend in the eastern Tibetan Plateau since the 19th century, with newer climate models able to simulate this change effectively and showing a significant impact of human activities on temperature change.