The impact of aging and urbanization on CO₂ emission in Chinese cities: an empirical analysis

Rapid aging and urbanization pose major challenges to global CO₂ reduction efforts, particularly in China. As such, effective carbon reduction strategies must account for their combined impact on emissions. However, existing research pays insufficient attention to the combined impact of aging and urbanization on CO₂ emissions and the underlying economic drivers. Furthermore, city-level analyses for projecting emissions related to these demographic shifts remain scarce. To address these limitations, this study employs an STIRPAT model using city-level data from China for 2010–2020 to estimate the combined effects of population aging and urbanization on CO₂ emissions. Then, we explore the economic drivers underlying this relationship. Finally, we project city-level CO₂ emissions driven by population aging and urbanization under different shared socioeconomic pathways (SSPs) in 2030–2060. Our findings suggest that: (a) The emission-increasing effect of aging outweighs the mitigating impact of urbanization, and together these opposing forces contribute to the overall rise in emissions. (b) Per capita disposable income and the size of the tertiary sector are key economic drivers of population aging, contributing to increased CO₂ emissions. The tertiary sector also significantly influences urbanization, which in turn facilitates emission reductions. (c) The relative contributions of CO₂ emissions from population aging and urbanization are similar under SSP1, SSP4, and SSP5. However, the absolute levels of CO₂ emissions resulting from the combined effects of aging and urbanization exhibit significant variation across cities under the SSP1–SSP5 scenarios. Based on the results, we offer policy recommendations to support carbon mitigation efforts.