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Alpine grassland ecosystems are thought to be the most sensitive ecosystems to climate change, yet the responses of their belowground biomass and potential climatic controls are poorly understood. Thirteen-year (2004 - 2016) time-series of observational belowground biomass data and environmental factors were analysed in a humid alpine Kobresia meadow on the Northern Qinghai-Tibetan Plateau. Results showed that the mean air temperature increased by 0.44 degrees C from 2004 to 2016, while annual precipitation remained relatively stable. The belowground biomass across all soil depths (0-10 cm, 10-20 cm, 20-40 cm) increased significantly, while aboveground biomass showed little change. The proportion of 0-10 cm belowground biomass decreased, whereas the other proportions both increased, which could be mostly attributed to variations in maximum air temperature. There was no significant relationship between aboveground biomass of plant functional groups and belowground biomass across all depths, indicating that the impact of maximum air temperature on belowground biomass should not be limited by aboveground biomass. The asymmetrical response of aboveground and belowground biomass under current climate fluctuations could provide new insights for the appropriate management of the alpine ecosystem.