Reproducibility of Holocene atmospheric CO2 records based on stomatal frequency
by Wagner F., Kouwenberg L. L. R., van Hoof T. B., Visscher H. (2004)
Friederike Wagner, Lenny L. R. Kouwenberg, Thomas B. van Hoof, Henk Visscher,
Palaeocology, Laboratory of Palaeobotany and Palynology, Utrecht University, Budapestlaan 4, 3584 CD Utrecht, Netherlands
In Quaternary Science Reviews 23: 1947-1954 – https://doi.org/10.1016/j.quascirev.2004.04.003 –
The majority of the stomatal frequency-based estimates of CO2 for the Holocene do not support the widely accepted concept of comparably stable CO2 concentrations throughout the past 11,500 years. To address the critique that these stomatal frequency variations result from local environmental change or methodological insufficiencies, multiple stomatal frequency records were compared for three climatic key periods during the Holocene, namely the Preboreal oscillation, the 8.2 kyr cooling event and the Little Ice Age.
The highly comparable fluctuations in the palaeo-atmospheric CO2 records, which were obtained from different continents and plant species (deciduous angiosperms as well as conifers) using varying calibration approaches, provide strong evidence for the integrity of leaf-based CO2 quantification.
Consistent in all records, the shifts in stomatal frequency indicate a change in the atmospheric CO2 concentration of 20–30 ppmv associated with the Preboreal oscillation.
The two data sets consistently reveal a century-scale interval of30 ppmv CO2 concentration changes with lowest CO2 levels centred around
8.2 kyr BP.
So far, the validation of stomatal frequency as a sensitive parameter to changing CO2 concentrations has basically been performed for individual species (see, Royer, 2001 for review).