Blue sky defense in low-carbon pilot cities: A spatial spillover perspective of carbon emission efficiency.

The improvement of carbon emission efficiency is crucial to the realization of the global carbon peaking and carbon neutrality goals. Based on the panel data of 282 cities from 2004 to 2018 in China, this paper employs the stochastic frontier analysis approach combined with the Sheppard distance function to calculate the total factor carbon emission efficiency of each city. Regarding the low-carbon pilot city policy as a quasi-natural experiment, we evaluate the impact of the pilot policy on carbon emission efficiency and its spatial spillover effect using the spatial difference-in-differences model. The results show that the pilot policy can significantly improve the carbon emission efficiency and has long-term dynamic effects. Also, the effect of the policy has spatial spillover, and has a positive impact on the neighboring cities. Mechanism analysis implies that optimal allocation of resources, energy conservation and green technology innovation make the low-carbon policy play an important intermediary role in promoting carbon emission efficiency. Besides, the effects of the pilot policy have obvious heterogeneity, especially cities in large, higher population densities and the north. These findings reveal that low-carbon pilot city policies are indispensable for both implementing the dual-carbon strategy and winning the defense for the blue sky.