Unraveling implementation gaps in China's urban climate pioneers: A decomposition analysis and its implications for latecomers

Pioneering urban trials represent the frontier of global climate mitigation. China has strategically deployed three batches of low-carbon pilot cities to accelerate nationwide decarbonization through ambitious targets. Yet it remains unclear whether these pledges have translated into effective implementation. This study combines KPI benchmarking, Tapio-LMDI analysis, and counterfactual simulations to assess 71 pilot cities. Results reveal a systematic gap between overall mitigation trends and city-level policy delivery. While average energy and carbon intensities declined by more than 30% from 2010 to 2021, 37% of cities failed to meet carbon intensity targets, and 51% missed their non-fossil energy goals. This shortfall was proportionally higher in later-batch cities, where fossil energy reliance, including thermal power generation, remained a predominant factor in emission trajectories. Decomposition shows that the expansion of non-fossil energy plays a critical role in alleviating such constraints and is becoming increasingly important for achieving deep decarbonization and decoupling. Counterfactual analysis further indicates that fully closing the implementation gaps could have avoided over 310 Mt CO 2 (an 8% reduction compared to actual 2021 emissions), with 85% of this mitigation potential concentrated in third-batch cities and could have enabled universal decoupling. These findings demonstrate that the effectiveness of urban decarbonization depends not only on target ambition but also on strict compliance and structural transition. Bridging the implementation gap is therefore essential to avert structural decarbonization delays in developing economies.