Impact of population agglomeration in big cities on carbon emissions.

The study explored the influencing mechanism of population agglomeration in large cities on carbon emissions, including technological innovation, industrial structure, and transportation effects. Moreover, we attempt to explore the nonlinear impact of population agglomeration in large cities on carbon emissions. We used the panel data of 207 big cities with a permanent resident population of more than 1 million to study the relationship between population agglomeration and carbon emissions. We found that population agglomeration to big cities increased urban carbon emissions significantly. The results of the mechanism analysis showed that population agglomeration to big cities raised carbon emissions by the channel of industrial structure and transportation effects. The channel of technological innovation effect decreased carbon emissions but did not offset the growth of carbon emissions caused by industrial structure and transportation effects. Nonlinear estimation findings demonstrated that the impact of population agglomeration on carbon emissions was different in big cities with varying levels of population.