Measurements, spatial differences, and convergence analysis of carbon offset in the Yangtze River economic belt

In the context of China’s dual carbon goals and the strategic positioning of the Yangtze River Economic Belt as a pilot zone for carbon-peak and carbon-neutrality policies, understanding the spatiotemporal evolution and convergence of regional carbon offset capacity is essential for designing differentiated low-carbon development pathways. This study utilizes panel data from 107 prefecture-level cities along the Yangtze River Economic Belt from 2006 to 2017 to investigate the “catch-up effect” in carbon offset capacity and trace the temporal and spatial evolution of carbon offset gaps. Employing spatial dependence analysis alongside absolute and conditional \( β \) -convergence testing, the study examines convergence trends in the carbon offset gap. The findings reveal that: (1) The carbon offset gap across the Yangtze River Economic Belt exhibited an overall upward trend, peaking around 2011–2012, with values declining progressively from downstream to midstream and upstream regions. (2) The carbon offset gap first increased and then decreased over the sample period; approximately 30% of the variation was attributed to intra-regional differences, a proportion that remained stable over time, while inter-regional disparities and density-related heterogeneity accounted for approximately 45% and 25%, respectively, with mild inverse fluctuations. (3) Convergence analysis identified significant absolute and conditional \( β \) -convergence across the belt, revealing a clear catch-up tendency; the coefficient of variation nevertheless increased over the full sample period, indicating \( σ \) -divergence, although its decline after 2014 signaled an emerging \( σ \) -convergence trend. The convergence rate was highest in the upstream section, followed by the midstream and downstream sections. Based on these results, the study proposes regionally differentiated policy recommendations: enhancing carbon sink capacity in the upstream section, transitioning the midstream section into a low-carbon transition hub, and achieving substantial carbon emission reduction in the downstream section. Additionally, a collaborative support system should be established, incorporating green finance mechanisms, evaluation frameworks, and an integrated carbon monitoring and accounting platform to facilitate coordinated low-carbon development across the Yangtze River Economic Belt.