A Catalyst for Emissions Reduction or a Barrier to Carbon Mitigation? The Impact of New-Type Infrastructure on Carbon Emissions in China

New-type infrastructure (NI) may increase carbon emissions through scale expansion while reducing them through technological progress, but systematic empirical testing of these competing effects remains limited. Using panel data for 30 Chinese provinces from 2013 to 2024, this study examines the nonlinear effects of NI on carbon emissions within a two-way fixed-effects framework, and employs the system generalized method of moments (GMM) and instrumental variable approaches to address potential endogeneity arising from dynamic panel bias, omitted variables, and other sources. We then examine industrial structure rationalization and green technological innovation as mediating variables, estimate spatial dependence with a spatial Durbin model, and combine particle swarm optimization–support vector machine (PSO-SVM) forecasting with alternative scenario assumptions. The evidence supports an inverted U-shaped association between NI and carbon emissions. Both mediating variables are significant, but the nonlinear relationship is found only in the central and western regions; it is not significant in the eastern or northeastern regions. NI also has significant cross-regional spatial spillover effects. Across the four scenarios, emissions ultimately decline, the green-transition scenario reaches the earliest and lowest peak, and rapid NI development produces greater pressure in the near term. These results characterize NI as a stage-dependent and spatially connected driver of emissions and support differentiated regional implementation of the Digital China and Beautiful China strategies.