Exploring the relationship between city size and carbon emissions: An integrated population-land framework

Abstract

As global climate change intensifies and urbanization accelerates, research on urban climate change has become a global concern. Urban decision-makers must determine optimal city sizes to achieve net-zero emissions. However, previous studies have mainly focused on average relationships between city size and carbon emissions, overlooking non-linear dynamics. This study used urban scaling laws to investigate relationships between city size and carbon emissions from population and land perspective across 294 Chinese cities. Results showed a sub-linear relationship between urban population size (UPS) and carbon emissions and a super-linear relationship between urban land size (ULS) and carbon emissions. Regionally, cities in central regions demonstrated higher carbon emission performance than those in western and eastern regions. The land perspective indicated lower carbon emission performance compared to the population perspective. Both perspectives revealed non-linear relationships between city size and urban scaling exponent for carbon emissions, characterized by multiple minima. Multiple city sizes can achieve optimal carbon emissions; however, only one ULS is ideal for a specific city size to ensure environmental sustainability. This study provides valuable policy insights for decision-makers in formulating reasonable low-carbon strategies.