This research attempted to investigate the impact of urbanization and spatial agglomeration on carbon emissions. To achieve the goal, the dynamic panel data model was employed to explore the nonlinear relationship between urbanization and carbon emissions for 166 cities in China taking the period 2005-2015, and the Gini coefficient of urban population size distribution in 15 urban agglomerations were calculated to analyze whether the spatial agglomeration of cities contributed to environmental protection. The results show that there is an inverted U-shaped curve between urbanization and carbon emissions; high-level urbanization development helps reduce carbon emissions; the spatial agglomeration of cities can contribute to carbon reduction to a certain extent based on the empirical results of the spatial agglomeration promotes the early arrival of the inflection point in the inverted U-shaped relationship between urbanization and carbon emissions; and the improvement of urban agglomeration level can present an abatement effect on carbon emissions at a lower urbanization level, which enhances the positive environmental effect of urbanization development compared with the decentralized urban distribution model. Furthermore, there is a significant U-shaped relationship between spatial agglomeration and carbon emissions, which indicates that the scientific planning of urban clusters will achieve economies of scale and agglomeration effect, thereby reducing carbon emissions. These findings contribute to complement the existing literature as well as provide some implications related to sustainable urban development for policymakers.
Keywords: Carbon emissions; China; Environment; Scale effect; Spatial agglomeration; Urban agglomeration; Urbanization.