Continental Rigidity in the Tropics Shapes Earth’s Climate state

Global pCO₂ levels have fluctuated significantly throughout the Phanerozoic, closely aligning with Earth’s warm, ice-free periods and cold, glacial climates. However, the extent to which these variations in pCO₂ are linked to weathering processes remains a topic of active debate. In this study, we quantify the effective elastic thickness of all major modern terrains and reconstruct their paleogeographic positions over the past 250 million years. We then estimate the weighted average continental effective elastic thickness within the tropics (e.g., within 10°, 15°, and 20° of the equator) and compare these values to global pCO₂ levels over time. Our analysis reveals a strong positive correlation between global pCO₂ levels and the weighted average continental effective elastic thickness in the tropics. We propose that variations in the mechanical strength of continents at low latitudes are linked to transitions between cold and warm climatic states. Specifically, when non-rigid continents drift into tropical regions, weakened and deformed rocks become more susceptible to exhumation and erosion in the warm, wet tropics, thereby enhancing Earth’s capacity for carbon sequestration through chemical weathering. Conversely, when rigid continents dominate the tropics, exhumation and erosion are inhibited, leading to relatively high atmospheric pCO₂ levels. If validated, we apply this correlation between continental rigidity and global pCO₂ to project future pCO₂ levels based on the assembly of the next supercontinent. Our findings suggest that, excluding human influence, global pCO₂ levels could increase fivefold over the next 250 million years. This underscores the critical role of continental strength, beyond just lithology or rock composition, in the tropics in driving physical and chemical weathering processes that shape Earth's climate state.