Quantification of silicate weathering CO2 consumption in semi-arid and arid eolian-dominated regions since the late Pliocene

Semi-arid and arid regions have traditionally been regarded as peripheral to the global carbon cycle because of their presumed low silicate weathering rates, resulting in their systematic omission from long-term carbon budget assessments. Direct quantification on CO₂ consumption by silicate weathering (CO₂_(SIW)) in eolian-dominated drylands, however, remains scarce. Here we reconstruct both silicate weathering rate (R_CO₂) and annual CO₂ consumption (CO₂_(SIW)) flux using red clay and loess–paleosol sequences from the Chinese Loess Plateau (CLP). We demonstrate that variability in eolian mass accumulation rate (MAR), rather than intrinsic silicate weathering intensity (R_CO₂), exerted the primary control on CO₂_(SIW), reflecting persistently low to moderate chemical weathering across the CLP. Our results further reveal a rise in CO₂_(SIW) from ~3.3 Tg C yr⁻¹ to ~12.3Tg C yr⁻¹ between 4.0 and 1.0 Ma, followed by a subsequent decline to ~9.0 Tg C yr⁻¹, broadly coincident with the late Pliocene decrease in atmospheric CO₂... These findings provide the first long-term quantitative budget of silicate weathering–mediated CO₂ drawdown in drylands and highlight the previously underrecognized role of semi-arid and arid eolian systems as negative feedback on atmospheric CO₂ over both million-year and orbital timescales.