Tree ring derived summer temperature variability over the past millennium in the western Himalayas of northern Pakistan

Long-term high resolution climate proxies are essential for understanding climate variability particularly, in regions such as the western Himalayas of northern Pakistan, where few long-term climate records are available. Using standard dendrochronological methods, an 1132-year (882 to 2013 C.E.) tree-ring chronology of Juniperus excelsa M. Bieb was established from the western Himalayas, northern Pakistan (WHNP). Tree growth was negatively and significantly (r = -0.65) correlated with the growing season (June-July) mean temperature, and positively and weakly (r = 0.22) associated with precipitation. This inverse relationship of tree radial growth with temperature and positive association with precipitation demonstrated that forest growth is sensitive to high temperature related drought. Utilizing a reliable STD chronology and robust reconstruction model, a 928-year (1086 to 2013 C.E.) mean temperature reconstruction was developed for the WHNP using the substantial negative correlation between the summer temperature and standard tree ring-width chronology. According to statistical validation, the reconstruction accounted for 41.6% of the climatic variation for the period of 1956-2013 C.E. instrumental period. Individual extreme-warm periods occurred in 1093 C.E. (29.42 degrees C) and extreme cold periods in 1088 C.E. (26.99 degrees C) observed during the past 928 years. The reconstruction's multi-taper method (MTM) spectral analysis reveals significant (p < 0.05) 2-3-year and 63.8-year cycles. Since the 2-3-year cycle occurred within the range of ENSO variation, which indicates that ENSO had an impact on the regional temperature in our studied area.