A tree ring-based spring temperature reconstruction for the Hindu Kush region in northern Pakistan

Annually resolved and absolutely dated proxy archives are necessary for contextualizing the rate and amplitude of anthropogenic climate change. High-resolution climate reconstructions are particularly important for remote regions where instrumental meteorological observations are limited in space and time. Here, we develop a robust, 260-year-long tree-ring width chronology from 32 Himalayan cedars (Cedrus deodara D. Don), which grew around 3000m asl in the Kumrat Valley of the Hindu Kush region in northern Pakistan. Growth-climate response analyses reveal a significant negative correlation of -0.631 between our new standard chronology and March-April minimum temperatures (p <0.001, n =51). This inverse relationship between radial tree growth and early spring temperatures, together with positive correlations against precipitation totals at the onset of the growing season, suggest that warming-induced drought is the most limiting factor of sub-alpine forest growth in the Kumrat Valley. We then use the inverse growth-temperature association to reconstruct March-April minimum temperatures from 1812–2018 CE. The reconstruction explains 40% of the instrumental record back to 1967, and exhibits the coldest and warmest spring conditions in 1815-1864 (6.67 ±0.21°C) and 1918-1927 (8.11 ±0.43°C), respectively. This pioneering study is indicative of the dendroclimatological potential in the Hindu Kush, where samples from living and relict trees of different species and elevational bands should be collected for advanced temperature and hydroclimate reconstructions.