Nonlinear Climate‐Transportation Emissions Dynamics and Forecast Persistence in the United States and China

ABSTRACT

Transportation systems are a major and growing source of global carbon emissions, accelerating climate change and exacerbating extreme temperature risk. This study investigates the long‐term dynamics of transportation carbon emissions (TCE) and temperature in China and the United States from 1970 to 2023, employing an integrated framework that combines Mann‐Kendall and Theil‐Sen trend analyses, decomposition‐assisted forecasting, and Quantile‐on‐Quantile (Q‐Q) analysis. To ensure the robustness of the results, a bandwidth sensitivity test is used. The results show significant warming trends across both countries, with urban warming rates ranging from 0.018°C to 0.033°C yr ^{− 1} . Structural break diagnostics reveal major regime transitions during the mid‐to‐late 1990s and early 2000s. Supplementary stationarity diagnostics further demonstrate substantial long‐memory persistence and strong nonstationarity in transportation‐emissions systems, particularly in China. Forecast results indicate continued warming through 2035 in both countries, while transportation‐emissions trajectories diverge markedly. The United States exhibits comparatively slower emissions growth and partial stabilization tendencies, whereas China shows persistent long‐term emissions acceleration and stronger structural persistence. Q‐Q analysis further reveals stronger upper‐tail temperature‐emissions synchronization in China ( r = 0.747) than in the United States ( r = 0.630), indicating more pronounced coupling under high‐emission and elevated‐warming regimes. The study provides governments with tailored transportation decarbonization policy measures.