Global increase in plant carbon isotope fractionation following the Last Glacial Maximum caused by increase in atmospheric pCO2

Changes in the carbon isotope composition of terrestrial plant tissue (delta C-13) are widely cited for evidence of shifts in climate, vegetation, or atmospheric chemistry across a wide range of time scales. A global compilation of delta C-13 data from fossil leaves and bulk terrestrial organic matter (TOM) spanning the past 30 k.y., however, shows wide variability and no discernable trend. Here we analyze these data in terms of a relative change in net carbon isotope fractionation between the delta C-13 value of plant tissue and that of atmospheric CO 2 [Delta C-13 = (delta C-13(CO2) - delta C-13)/(1 + delta C-13/1000)] and identify a global 2.1 parts per thousand shift in leaf and TOM Delta C-13 that is synchronous with a global rise in pCO(2) documented from ice core data. We apply a relationship describing the effect of pCO(2) on Delta C-13 to the global record of Delta C-13 change documented here to reconstruct pCO(2) levels across the past 30 k.y. Our reconstructed pCO(2) levels are in excellent agreement with the ice core data and underscore the potential of the global terrestrial delta C-13 record to serve as an accurate pCO(2) proxy.