*3.1. Explained Variable*

The explained variable in this study is the environmental pollution variable, as measured by carbon emissions (Carbon) at the city level. On the one hand, with the popularity of "carbon neutrality" and "carbon capping", carbon emissions are undoubtedly an important element of current social and environmental issues, and are highly representative [48]. On the other hand, China is still dominated by carbon-based energy sources [49], and using carbon emissions can more accurately cover the environmental impact of energy factors.
