How Upgrading of Provincial Development Zones Reduces Urban Carbon Emission: Evidence from a Time-Varying DID Analysis

This study examines the impact of upgrading provincial development zones on urban carbon emission reduction in China, a vital policy instrument for achieving the nation’s dual objectives of economic growth and green development under the “carbon neutrality and carbon peak” framework. Utilizing panel data from 276 Chinese cities spanning 2006 to 2019, this study employs a time-varying difference-in-differences model to empirically assess the effects of these upgrades. The findings indicate that these upgrades significantly reduce urban carbon emissions through policy, agglomeration, and regulatory effects. The heterogeneity analysis further reveals that the policy’s effectiveness is amplified by higher levels of government participation, increased attention to environmental protection, and greater urban emission reduction pressures. Moreover, while the policy facilitates carbon emission reductions in neighboring cities through spatial spillover effects, it does not achieve synergistic control over multiple pollutants, showing no significant impact on other industrial pollutants emissions. These findings provide value insights for policymakers aiming to balance economic development with environmental sustainability.