Century-scale shifts in early holocene atmospheric CO2 concentration

The inverse relation between atmospheric carbon dioxide concentration and s tomatal frequency in tree leaves provides an accurate method for detecting and quantifying century-scale carbon dioxide fluctuations. Stomatal frequen cy signatures of fossil birch leaves reflect an abrupt carbon dioxide incre ase at the beginning of the Holocene. A succeeding carbon dioxide decline m atches the Preboreal Oscillation, a 150-year cooling pulse that occurred ab out 300 years after the onset of the Holocene. In contrast to conventional ice core estimates of 270 to 280 parts per million by volume (ppmv), the st omatal frequency signal suggests that early Holocene carbon dioxide concent rations were well above 300 ppmv.