Winter vs. summer temperature variations on the southeastern Tibetan Plateau, 1718–2005 CE

Abstract

The annual mean temperature on the Tibetan Plateau (TP) has strongly increased over the past few decades, with larger warming in winter than in summer. Whether this different amplitude of change between seasons has persisted over longer time-scales in the past remains poorly understood, limiting our understanding of the mechanisms responsible. Here, we apply multivariate regression analysis and ensemble empirical mode decomposition (EEMD) to decompose winter (TDJF) and summer (TJJA) temperature reconstructions over the 1718–2005 CE period for the southeastern TP to investigate similarities and differences between winter and summer temperature changes, over multiple time-scales, as well as the driving factors behind the seasonal differences. The results reveal that the TDJF and TJJA reconstructions were significantly correlated throughout the study period, with the magnitude of the TDJF variations approximately six times greater than the TJJA variations. When the two reconstructions were decomposed over multiple time-scales, it was found that the consistency between winter and summer temperature reconstructions only existed at inter-annual scale. Assessing the driving factors, the main contributions to the TJJA and TDJF changes at the inter-annual and inter-decadal scales appear to be mainly the El Niño–Southern Oscillation (ENSO). The Pacific Decadal Oscillation (PDO) contribution was important to TJJA and TDJF changes at multi-decadal scales. Furthermore, we found that orbital parameters and the Atlantic Multidecadal Oscillation (AMO) was a major contributor to the changes in TJJA and TDJF at centennial scales, respectively. Both the TJJA and TDJF have a significant long-term increasing trend since c. 1850, mainly attributed to anthropogenic forcing. The detected similarities and differences between TDJF and TJJA at multiple time-scales provide new perspectives on the understanding the mechanisms behind climate change on the Tibetan Plateau and even entire East Asia.