Although global warming over the past century has been confirmed, the response of different regions to it is still uncertain. We developed a tree‐ring width chronology based on tree‐ring samples from juniper trees from the Xiqing Mountains in the northeast Tibetan Plateau, the central headwater area of the Yellow River. Using this tree‐ring chronology, the minimum winter half‐year (October–April) temperature for the research area was reconstructed for the past 425 years. The reconstruction shows that temperature variability was minimal over past four centuries prior to the warming that began in 1941. During the 50 years from 1941 to 1990, the minimum temperature of the winter half‐year increased 2.5 °C. This degree of warming relative to the past 400 years suggests that the eastern Tibetan Plateau is highly sensitive to global warming. Copyright © 2007 Royal Meteorological Society

Within the mountain altitudinal vegetation belts, the shift of forest tree lines and subalpine steppe belts to high altitudes constitutes an obvious response to global climate change. However, whether or not similar changes occur in steppe belts (low altitude) and nival belts in different areas within mountain systems remain undetermined. It is also unknown if these, responses to climate change are consistent. Here, using Landsat remote sensing images from 1989 to 2015, we obtained the spatial distribution of altitudinal vegetation belts in different periods of the Tianshan Mountains in Northwestern China. We suggest that the responses from different altitudinal vegetation belts to global climate change are different. The changes in the vegetation belts at low altitudes are spatially different. In high-altitude regions (higher than the forest belts), however, the trend of different altitudinal belts is consistent. Specifically, we focused on analyses of the impact of changes in temperature and precipitation on the nival belts, desert steppe belts, and montane steppe belts. The results demonstrated that the temperature in the study area exhibited an increasing trend, and is the main factor of altitudinal vegetation belts change in the Tianshan Mountains. In the context of a significant increase in temperature, the upper limit of the montane steppe in the eastern and central parts will shift to lower altitudes, which may limit the development of local animal husbandry. The montane steppe in the west, however, exhibits the opposite trend, which may augment the carrying capacity of pastures and promote the development of local animal husbandry. The lower limit of the nival belt will further increase in all studied areas, which may lead to an increase in surface runoff in the central and western regions.

Climate change has been thought to drive the accelerated expansion of global drylands. However, many studies reveal that Arid Central Asia (ACA) has been warming and wetting in recent decades, representing an anomalous response to global climate change. Given that ACA is composed of complex ecosystems and landforms, it is not clear whether or not this trend is uniform in this topographically heterogenous region. Here, we integrate the Google Earth Engine and ERA5-Land reanalysis data to study the trend of changes, since the 1980s, in temperature and precipitation in the Tianshan Mountains and the surrounding deserts, collectively referred to as the Tianshan and Desert Ecozone, which is in Northwest China. Our results show that only 20.4% of this area is becoming both warmer and wetter, which occurs mainly in the altitudes above 2800 m (Tianshan Ecozone). All three alpine ecosystems (coniferous forests, alpine meadow, and nival zone) in the Tianshan Ecozone exhibit similar warming and wetting trends, including of elevation-dependent wetting on the specific altitude range. In contrast, the low-lying oasis where human activities are mostly concentrated is undergoing warming and drying, which will face a greater threat of drought projected under three emissions scenarios (SSP1-2.6, SSP2-4.5, and SSP5-8.5). These results highlight the importance of considering the differences of climate change in different altitude gradients and different ecosystems when studying climate change in drylands.