Contribution of urban expansion to surface warming in high-altitude cities of the Tibetan Plateau

Large-scale climate change on the Tibetan Plateau (TP), the world's Third Pole, has attracted extensive attention, while studies of urban climate on the TP have been sporadic. Here, we quantify urban expansion on the TP and its contribution to surface warming of typical plateau cities based on existing literature, observations, and numerical simulations. Large-scale warming of the surface atmosphere over the TP during 1975-2021 is estimated to be 0.31 [0.19 to 0.47] degrees C decade(-1) based on a set of rural meteorological sites, while the atmospheric warming of six typical highland cities on the TP during the same period is estimated to be 0.44 [0.31 to 0.53] degrees C decade(-1). This means that urbanization contributed about 30% of the warming in these cities. Lhasa is one of the cities with the strongest warming over the TP. The contribution of urban expansion to Lhasa's air temperature increase is approximately 40%, which can be estimated using both observations and numerical simulations. The urban expansion footprint of Lhasa and its contribution to the spatial pattern and diurnal variation of atmospheric and land surface warming are quantified. The contribution of urbanization to the near-surface air temperature and land surface temperature of Lhasa from 2000 to 2020 is estimated to be 0.44 [0.39 to 0.49] degrees C and 1.44 [1.32 to 1.56] degrees C, respectively. These results provide potential global implications for urban studies in plateau areas.