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℃)and extreme cold periods in 1088 C.E.(26.99℃)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.