Background: Transportation has become the second-largest source of global carbon emissions. Promoting low-carbon development by means of public transport and green travel and analyzing the mechanism and path of the carbon emissions reduction effect of public transport have become key to reducing carbon emissions in the transportation field and achieving “carbon peak and carbon neutrality”. Methods: The data from 30 provinces (2010–2019) were extracted from China Emission Accounts and Datasets (CEADs), China Energy Statistical Yearbook, China Statistical Yearbook, and China Automobile Statistical Yearbook. The two-way fixed-effect model was used to explore the carbon emissions reduction effect of public transport development level. The mediating-effect model was used to verify the transmission role of energy consumption in the carbon emissions reduction effect of public transport development level. Results: The study suggests that the public transport development level and CO₂ emissions are negatively correlated, showing an “Inverted U-shaped” curve relationship. Energy consumption is the transmission path of the carbon emissions reduction effect of public transport development level. The public transport development level adjusts the energy consumption structure through the traffic substitution effect, energy input optimization effect, and industrial structure optimization effect and then acts on carbon emissions. Moreover, the contribution rate of energy consumption is about 4.22%. In addition, regional heterogeneity is present in the transmission path of the carbon emissions reduction effect of public transport development level based on energy consumption. The carbon emissions reduction effect of public transport development level is more significant in the central and western regions than the eastern and northeast regions of China. Conclusion: The transmission mechanism of energy consumption in the carbon emissions reduction effect of public transport is worthy of attention. To promote low-carbon and circular development in the transportation sector, it is urgent to accelerate the green upgrading of transportation infrastructure, promote the low-carbon transformation of energy production and consumption, promote carbon emissions reduction in public transport, and strengthen the linkage regulation between effective government and an effective market.

Low-carbon city construction (LCC) is an important strategy for countries desiring to improve environmental quality, realize cleaner production, and achieve sustainable development. Low-carbon cities have attracted widespread attention for their attempts to coordinate the relationship between environmental protection and economic development. Using the panel data from 2006 to 2017 of prefecture-level cities in China, this study applied the difference-in-differences (DID) method to analyze the effects of LCC on the total factor productivity (TFP) of the cities and its possible transmission mechanism. The results show significantly positive effects on TFP, but the effects on each component of TFP are different. Although the LCC has promoted technical progress and scale efficiency, it has inhibited technical efficiency. The accuracy of the results has been confirmed by several robustness tests. Mechanism analysis showed that the pilot policy of low-carbon cities has promoted technical progress and scale efficiency by technological innovation and the upgrading of industrial structure, but resource mismatches among enterprises have been the main reason for reduced technical efficiency. Regional heterogeneity analysis showed that the effects on TFP in the eastern region have been more significant than in the central and western regions. In the eastern region, they have promoted technical progress, while in the central and western regions, they have promoted technical progress and scale efficiency but hindered technical efficiency. This paper presents our findings for the effects of LCC on economic development and provides insightful policy implications for the improvement of technical efficiency in low-carbon cities.

As an essential reform of China’s environmental regulatory policy, the environmental protection tax reform achieves a smooth transition from the emission fee system to the environmental protection tax system according to the principle of tax burden leveling. With the quasi-natural experiment of the introduction of the Environmental Protection Tax Law, this paper examines the effect of environmental protection tax reform on total factor productivity of heavily polluting firms using a difference-in-difference approach based on empirical evidence of Chinese listed companies from 2015 to 2020. It is found that environmental tax reform can significantly increase the level of total factor productivity of heavily polluting firms, and the results remain robust to robustness tests using the OP method, the GMM method to re-measure the total factor productivity of heavily polluting enterprises and the use of different industry classification criteria, with the mechanism of action mainly coming from the technological innovation effect and capital allocation optimization. In addition, the effect of environmental tax reform on total factor productivity of heavily polluting firms is heterogeneous across regions and industries, with the total factor productivity of firms in heavily polluting industries in the eastern region being least affected by environmental tax policies and state-owned enterprises with heavy property rights structures being most affected by environmental tax reform.

This paper evaluates the impact of the conversion of new and old driving forces of economic growth on air quality. Based on the policy shock of the establishment of the Shandong pilot zone, this paper took the monthly air quality index (AQI) as a measurement indicator and adopted the Regression Discontinuity Design (RDD) method. It was found that the conversion of new and old driving forces significantly improved air quality, and this effect was still robust for different bandwidths. The examination of individual pollutants revealed that the improvement in air quality (AQI) came mainly from the reduction in the levels of five pollutants in the air: PM_2.5, PM₁₀, SO₂, CO, and NO₂. Moreover, through the convergence analysis, it was found that the air pollution governance effect of the conversion of new and old driving forces had significant $\beta$ convergence characteristics. The convergence characteristics were still robust even considering control variables and spatial factors, thus indicating that the conversion of new and old driving forces had a synergistic governance effect on air pollution control.