Observational confirmation and dendrochronological implication of increasing temperature and precipitation covariance on the northeastern Tibetan Plateau

Living and relict Qilian juniper (Juniperus przewalskii Kom.) trees from the northeastern Tibetan Plateau provide a unique paleoclimate archive spanning centuries to millennia. Various climate signals reflected by Qilian Juniper tree-ring records from different elevations inspire us to investigate the temperature and precipitation covariance along the altitude. Here, we analyses temperature and precipitation measurements from 60 meteorological stations between 1139 and 3663 m asl on the northeastern Tibetan Plateau. We find that summer temperature and precipitation are positively correlated at higher elevations, while they show an inverse relationship at lower elevations. We also observe that anthropogenic warming has led to wetter (drier) conditions at higher (lower) elevations. Not captured by gridded climate data, our results suggest that tree ring-based hydroclimate reconstructions from arid Asian mountain systems are localised representations. We argue that warming-induced convective precipitation is altering the hydrological cycle of Asian ‘Water Towers’ through changes in plant growth, vegetation composition, snow cover, glacier extent, and river runoff.