| Abstract： |
Global warming has a significant impact on the ecosystem of the high-altitude areas of the Tibetan Plateau, such as land degradation and the rapid retreat of glaciers. It is important to understand the effects of global warming occurring over hundreds or thousands of years. However, the long-term reconstruction of temperature is still lacking for the region of Western Sichuan Plateau (WSP). In this study, we reconstructed summer (June-July) temperatures back to 1383 for the WSP region based on a significant positive correlation between the standard chronology and summer temperature. The reconstruction passed statistical tests and explained 55.4% of the climatic variance in the period for which data are available (1962-2005). There have been five periods with warm summers and five with cold summers during the past 623 years. Warm periods occurred in 1383-1445, 1525-1590, 1700-1724, 1825-1870, and 1930-1960, while relatively cold periods occurred in 1446-1524, 1591-1675, 1725-1824, 1900-1929, and 1961-1990. A comparison with observed data and regional temperature reconstruction series shows that the reconstruction has a high degree of consistency and is indicative and reliability. The spatial correlation was analysed with Climatic Research Unit gridded data to detect the spatial representativeness of the reconstruction, confirming that the reconstruction has a strong regional temperature signal for the WSP. Furthermore, ensemble empirical mode decomposition indicates quasi-oscillations of 2.8-3.3, 6.4-8.3, 11.1-14.2, 25-38.4, 89, and 138 years in the reconstructed temperature time series during the past 623 years. El Nino Southern Oscillation cycles, solar activity, and Atlantic multi-decadal oscillation may be the primary forcing factors. Meanwhile, the coordinated action of temperature-induced drought stress with a late growing season related to delayed snowmelt can potentially be attributed to the divergence problem (observed around 2005). |
