Global lithium isotopes reveal climatic and topographic thresholds in silicate weathering

Silicate weathering regulates Earth's long-term climate, yet the precise competing influences of climate and tectonics remain debated. This uncertainty largely stems from nonlinear responses and poorly constrained global thresholds related to climate, topography, and weathering intensity, which obscure the interpretation of key weathering proxies, such as lithium (Li) isotopes. Here, we compile a global riverine dataset of dissolved Li isotopes (δ⁷Li_diss) and fluxes to evaluate their controlling factors and identify critical thresholds. We find that climate and topography are the dominant controls, exerting nonlinear influences characterized by global thresholds. Identifying these thresholds provides a quantitative framework for understanding climate-topography-weathering feedbacks, which translates isotopic signals directly into environmental parameters. This may help improve the interpretation of seawater δ⁷Li records by delineating boundaries between weathering regimes and facilitating the reconstruction of past weathering fluxes and CO₂ consumption rates directly from isotopic records. Moreover, this framework offers testable boundary conditions for long-term climate shifts and rapid hyperthermal events.