Comprehensive evaluation and identification of the critical regulatory determinants of carbon emission efficiency (CEE) are very important for China’s low-carbon transition. Accordingly, this paper first employs an undesirable global super-hybrid measure approach to calculate the CEE of China’s iron and steel industry (ISI). We then further use spatial error and threshold regression models to examine the spatial and non-linear effects of heterogeneous environmental regulations on CEE, respectively. Our empirical results show that (1) CEE varies significantly across China’s regions, with the eastern region having the highest CEE score, followed by the western and central regions, with the northeast region ranking the lowest; (2) command-and-control and market-incentive regulations both promote CEE, whereas the public participation approach does not significantly contribute to performance gains; (3) all three types of environmental regulations exhibit a non-linear threshold effect on CEE; (4) openness level, technological progress, and industrial concentration enhance efficiency gains, while urbanization level exerts a negative impact on CEE. Our findings have important implications for the design of environmental regulations.

As the problem of global climate change becomes more severe, countries have proposed the goals of carbon capping and carbon neutrality. Green finance is an essential capacity support for achieving carbon peaking and carbon neutrality, and it can guide and stimulate social capital to invest in low-carbon industries and initiatives via marketbased mechanisms. Based on the panel data of Chinese prefecture-level cities from 2006 to 2020, this paper empirically examines the impact of green finance on carbon emission efficiency using a two-way fixed-effects model, conducts a regional heterogeneity analysis, and examines the threshold effect of economic development level and the mediating role of regional innovation. The results indicate that, first, green finance contributes significantly to the improvement of carbon emission efficiency, and second, the level of regional economic development has a double threshold effect on the contribution of green finance to the improvement of carbon emission efficiency. Third, regional innovation is an important green finance channel for influencing carbon emission efficacy. The sensitivity of carbon emission efficiency to the green finance index demonstrates an inverted U-shaped trend. Fifth, the importance of green finance sub-dimensions in relation to carbon emission efficacy is as follows: green support, green credit, green insurance, green investment, green equity, green bond, and green fund. These findings provide theoretical support for green finance's role in promoting co-carbon efficiency and are valuable for policy formulation.

Regional carbon emission efficiency has differentiated characteristics under different economic development stages and patterns, and it is significant to identify such characteristics and formulate corresponding policies for high-quality regional development. Based on input-output data related to economic development and energy consumption, a comprehensive evaluation model of Super-SBM and Malmquist-Luenberger (ML) index was constructed to evaluate the spatial and temporal changes and driving forces of CEE, on the basis of which a proposal for collaborative carbon emission reduction zoning is proposed. The results indicated that the carbon emission efficiency (CEE) of the YRD shows a fluctuating upward trend with obvious spatial agglomeration characteristics, and the changes in CEE were closely related to the stage of economic development. The annual average CEE value during each period exhibited positive changes, indicating that economic development gradually shifted toward low carbonization. Moreover, the improvement of CEE gradually shifted from being driven by efficiency change to being driven by technological change. Finally, based on the carbon emissions and CEE characteristics of different cities, a carbon-neutral synergistic path is proposed in terms of industrial transformation, green development and technological support.