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Over geological timescales, mountain building or orogenesis is associated with increased weathering, the drawdown of atmospheric CO2, and global cooling. However, a multimillion-year delay appears to exist between peaks in low-latitude mountain uplift and the maximum extent of Phanerozoic glaciation, implying a more complex causal relationship between the two. Here we show that global silicate weathering can be modulated by orogeny in three distinct phases. High, young mountain belts experience preferential precipitation and the highest erosion. As mountains are denuded, precipitation decreases, but runoff temperature rises, sharply increasing chemical weathering potential and CO2 drawdown. In the final phase, erosion and weathering are throttled by flatter topography. We conclude that orogeny acts as a capacitor in the climate system, granting the potential for intense transient CO2 drawdown when mountain ranges are denuded; the mechanism suggests such a scenario potentially happening 10-50 x 10(6) years in the future.

Plain Language Summary Over timescales of tens of millions of years or more, plate tectonics can raise large mountain ranges. CO2 can be removed from the atmosphere through a complex series of processes involving the weathering of rocks, which depends on processes such as rainfall, which in turn is affected by the presence of mountains. The result is that mountain ranges are associated with a reduction of atmospheric CO2 and global cooling on these very long timescales. An analysis of geological data suggests a multimillion-year delay between peaks in mountain range uplift at low latitudes and the maximum extent of glaciation over the last 400 x 10(6) years. Our manuscript explains the delay using two numerical or computer models: a climate and circulation model and a geochemical model that simulates weathering processes. We show that weathering, and the implied reduction of atmospheric CO2, happens most intensely when mountain ranges are eroded, because the ability of weathering to remove CO2 depends not just on precipitation but also on the temperature of river runoff. Our mechanism intriguingly suggests such a scenario potentially happening 10-50 x 10(6) years in the future associated with projected changes to the height of the Tibetan plateau.