Climate Warming Amplifies the Contribution of High‐Altitude Cold Regions to Global Carbonate Weathering Carbon Sink

Abstract Carbonate weathering carbon‐sink (CWCS) is a critical yet inaccurately quantified component of terrestrial carbon sequestration. However, the mechanisms through which climate change and vegetation dynamics drive the spatial heterogeneity of CWCS remain unclear. We integrated multi‐source data to identify altitude thresholds and nonlinear response characteristics of CWCS driven by climatic and vegetation globally. Our findings show that global carbonate weathering sequestered 127.60 ± 7.70 Tg C yr −1 from 1950 to 2014, equivalent to 3.65% of global forest carbon sink. We identified a dichotomous pattern in CWCS at an altitude threshold of 3,000 m: rates decreased below but increased significantly above this elevation. This altitude threshold marks a fundamental shift in climate sensitivity and driving mechanisms, meaning that warming inhibits carbonate weathering in warm lowlands, while high‐altitude cold regions accelerate carbonate weathering through enhanced glacial snowmelt (percent contribution: 20.71%–38.96%) and vegetation–carbon dioxide feedback (NDVI threshold: 0.33–0.67). By 2100, global CWCS is projected to increase by 14.51%–24.90% compared to historical period (1950–2014). High‐altitude cold regions are projected to emerge as pivotal growth areas for CWCS in the future (2015–2100), contributing 45.02%–59.50% of newly added CWCS, despite accounting for only 28.41% of carbonate areas. Our results demonstrate that climate warming has transformed cold high‐altitude regions into indispensable engines for enhancing terrestrial carbon sink.