Based on the panel data of 108 prefecture-level cities in China from 2003 to 2018, the carbon emission effect of urban density was studied by establishing a dynamic panel model. We found that there was a significant negative correlation between urban density and carbon emissions, and the increase in urban density reduced carbon dioxide emissions. The nonlinear estimation results of urban density and carbon emission show that urban density has different impacts on carbon emission at different urban population levels. With the increase in population size, the carbon emission reduction effect brought by urban density growth decreases. In medium-sized cities, increased urban density leads to the greatest reduction in carbon emissions, followed by large cities with populations of less than 5 million. In megacities with a population size of more than 5 million, the carbon emission reduction effect of urban density is not significant. Our conclusion supports the proposition of building compact cities and provides decision support for the ideal of ‘beautiful China’ in the process of urbanization in China.

Although several studies have explained the effect of urbanization on China’s carbon emissions, most have focused on population urbanization, while ignoring the urban spatial form. This study investigates the impact of urban spatial form, measured by residential density, on the evolution of carbon emissions of 108 cities from 2003 to 2013 in China. The main results are as follows: (1) although urbanization significantly increases CO₂ emissions, urban spatial form measured by residential density produces a negative effect on CO₂ emissions in China.; (2) China has not become the “pollution haven” of foreign direct investment (FDI), instead, green FDI has reduced carbon emissions significantly; (3) the environmental dividends of low-carbon transformation have been observed in eastern and middle cities, but not in western ones. Therefore, establishing compact cities and traversing a low-carbon path is both feasible and necessary.

This study estimates the effects of the Sino-US trade liberalization on CO₂ emissions in China and its influencing mechanism. We used the exchange of CNY/USD as the instrumental variable to alleviate the endogeneity with the two-stage least squares method. Different from the existing literature focusing on implied carbon, we use panel data of 27 provinces in China from 1998 to 2018 to examine the relationship between the Sino-US trade liberalization and CO₂ emissions. We found that the Sino-US trade liberalization had a positive effect on the environment and reduced CO₂ emissions.