Nonlinear Relationship Between Carbon Emission Performance–Energy Efficiency Synergy and Urban Low-Carbon Resilience: Evidence from Technological Innovation Input

Against the backdrop of sustainable transition, the coordinated improvement of carbon emission performance (CEP) and energy efficiency (EE), as well as its relationship with urban low-carbon resilience (LCR), warrants further investigation. Using panel data for 289 prefecture-level and above cities in China from 2010 to 2023, this study measures CEP–EE synergy and LCR and employs spatial autocorrelation analysis, the spatial Durbin model (SDM), the system generalized method of moments (SYS-GMM), and a panel threshold model to examine their spatial, dynamic, and nonlinear relationships. The results show that: (1) Both LCR and CEP–EE synergy exhibit an overall upward trend, although their spatial evolution is not synchronized, and both display significant positive spatial autocorrelation. (2) The SDM results reveal a significant positive relationship between CEP–EE synergy and local LCR, together with a significant positive spatial indirect effect. (3) The SYS-GMM results show that CEP–EE synergy remains significantly and positively associated with LCR after accounting for the dynamic persistence of LCR and potential endogeneity, and this finding is supported by robustness checks. (4) The threshold test supports the existence of a single threshold in technological innovation input (TII). CEP–EE synergy is significantly and positively associated with LCR across different TII regimes, while exhibiting some stage-dependent variation. These findings indicate that the coordinated improvement of CEP and EE and its spatial linkages constitute an important dimension for understanding urban LCR, while their relationship also varies across TII conditions. The study provides empirical evidence for differentiated and regionally coordinated approaches to high-quality urban transition.