Abstract
Levels of atmospheric carbon dioxide constrain vegetation types and thus also non-biological uptake during rock weathering. That's the reasoning used to explain why CO2 levels did not fall below a certain point in the Miocene. Despite the occurrence of high rates of global silicate rock weathering likely to increase the drawdown of atmospheric CO2 — and hence temperatures — CO2 concentrations are thought to have stayed above about 180 parts per million throughout the past 24 million years (compared to about 385 p.p.m. today, and a 'pre-industrial' 280 p.p.m.). Based on terrestrial and geochemical carbon-cycle modelling simulations, Pagani et al. suggest that it may have been the actions of land plants that strongly attenuated long-term CO2 variability and helped prevent the onset of icehouse conditions. As CO2 falls to critically low levels due to increased chemical weathering, they find that vegetation activity is substantially reduced, compromising the capacity to further enhance silicate chemical weathering.
Published Version
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