Assessing spatiotemporal trends and drivers of collaborative governance for air quality and carbon emission control: Evidence from typical urban agglomerations in China

The collaborative governance for air quality improvement and carbon emission reduction (CGAC) within urban agglomerations is a complex system. Analyzing the spatiotemporal evolution and drivers within cities and among urban agglomerations is crucial for advancing urban sustainable development. This study targets three major Chinese urban agglomerations—the Beijing–Tianjin–Hebei and surrounding areas (BTHSH), the Fenwei Plain (SS) and the Yangtze River Delta (YRD). A CGAC evaluation index system is developed by integrating socio-economic and resource–environment factors, and a sequential-parameter synergy model is applied to calculate CGAC levels for 2013–2022. Spatial disparities, temporal trends and driving factors are examined using the Dagum's Gini coefficient, kernel density estimation and geographical detector methods. The results indicate a general upward trend in CGAC levels across the three urban agglomerations, accompanied by significant spatial disparities and a “core–periphery” polarization. Intra-regional gaps are narrowing, but inter-regional differences, particularly between the YRD and the SS, remain the main source of overall inequality. Key drivers include urban–rural disparities, market vitality, technological innovation, energy structure and industrial structure, whose non-stationary and interactive effects further enhance collaborative governance. The findings underscore the necessity of targeted interventions to address CGAC spatial disparities and leverage context-specific drivers for sustainable urban development, recommending both inter-agglomeration cooperation and intra-agglomeration integration through regionally differentiated strategies that optimize key influencing factors.