Urbanization and the Bipolarization of Carbon Emission Efficiency Across Chinese Cities

The commitment to peak carbon emissions before 2030 and the goal of achieving carbon neutrality by 2060 have placed carbon emission efficiency (CEE) at the center of China’s low-carbon development strategy. Although national policies have promoted energy conservation and technological upgrading, substantial heterogeneity in CEE persists across cities of different administrative and economic tiers. To examine this heterogeneity, we construct a city-level CEE index based on a stochastic frontier analysis (SFA) framework that explicitly treats CO2 emissions as an undesirable output. Based on a panel dataset covering 274 prefecture-level cities grouped into five categories from 2006 to 2022, we find that first-tier cities such as Shanghai and Beijing, with advanced technological capacity and strong support by the emission trading scheme (ETS), have shown an upward trend in improving their CEE, while middle-range cities remain locked in carbon-intensive trajectories. In particular, the lowest-level fifth-tier cities show a decreasing trend, implying a bipolarization of urbanization among cities. To address this bipolarization by urbanization, we examine the governance mechanisms of CEE using a second-stage Tobit model and find that governance factors related to urbanization—such as high labor quality and intensive land development in larger cities—have contributed to the widening gap in CEE. This implies that mitigating the negative consequences of urbanization is essential for achieving a carbon-neutral economy.