Do Low-Carbon and New Energy Demonstration City Pilots Generate Synergy? Evaluating the Dual-Pilot Policy on Carbon Emission Performance with Double Machine Learning

To advance sustainable development, China has introduced low-carbon city pilots (LCCP) and new energy demonstration city pilots (NEDC) as important institutional innovations. Using 2006–2023 panel data for 274 Chinese cities, we treat the dual-pilot policy of LCCP and NEDC as a quasi-natural experiment. We measure carbon emission performance (CEP) via a super-efficiency SBM-GML index incorporating social welfare and undesirable outputs, and use double machine learning (DML) to estimate the policy’s impact on CEP. We find the dual-pilot policy is associated with significantly improved urban CEP, with a stronger effect than either single pilot alone. Mechanism tests suggest the policy may contribute to improved CEP by promoting green technology innovation, industrial structure upgrading, and energy efficiency. Heterogeneity test results demonstrate that the dual-pilot policy yields more pronounced impacts in cities characterized by higher economic development, weaker path dependence, and more stringent environmental governance. Additionally, negative cross-regional spatial spillovers are identified. Different from the existing literature, this study integrates social welfare dimensions into CEP’s measurement framework and further validates that the dual-pilot policy generates more outstanding efficiency benefits compared with separate LCCP and NEDC pilots