d13CairCO2_LOESS_Interpolation

This is a smoothed curve of d13C in atmospheric CO2 from 16100 BCE to 2010 CE, based on data from Antarctic ice-cores (Eyer & Leuenberger, pers. comm.; Francey et al., 1999; Indermühle et al., 1999;Leuenberger et al., 1992) and flask data from two Antarctic stations (Halley Bay and Palmer Station) of the NOAA ESRL Carbon Cycle Cooperative Global Air Sampling Network.

If you use the interpolation curve, please ALWAYS refer to:
1) the NOAA ESRL Carbon Cycle Cooperative Global Air Sampling Network:
https://gml.noaa.gov/aftp/data/trace_gases/co2c13/flask/README_surface_flask_co2c13.html
2) the original publication of the interpolation curve:
Ferrio JP, Araus JL, Buxó R, Voltas J, Bort J (2005) Water management practices and climate in ancient agriculture: inference from the stable isotope composition of archaeobotanical remains. Vegetation History and Archaeobotany 14:510-517

Please cite also the original references of ice-core data:
Francey RJ, Allison CE, Etheridge DM, Trudinger CM, Enting IG, Leuenberger M, Langenfelds RL, Michel E, Steele LP (1999) A 1000-year high precision record of delta C-13 in atmospheric CO2. Tellus B 51:170-193
Indermühle A, Stocker TF, Joos F, Fischer H, Smith HJ, Wahlen M, Deck B, Mastroianni D, Tschumi J, Blunier T, Meyer R, Stauffer B (1999) Holocene carbon-cycle dynamics based on CO2 trapped in ice at Taylor Dome, Antarctica. Nature 398:121-126
Leuenberger M, Siegenthaler U, Langway CC (1992) Carbon isotope composition of atmospheric CO2 during the last ice age from an Antartic ice core. Nature 357:488-490

IMPORTANT NOTE: this dataset should be only used to apply the interpolation curve,
e.g. as reference for d13C in archaeobotanical, wood charcoal or tree-rings
Original values from ice-cores and NOAA ESRL should be retrieved (and cited) from their original sources

BEAR IN MIND THAT THIS IS AN APPROXIMATION:
1) Ice core data, particularly regarding trapped CO2, has considerably dating errors
2) The data is based on Antarctic ice cores only. Considerable spatial variability in CO2 is expected

METHODS:
Due to the much higher time resolution available for the last 2 centuries, the smoothing was performed dividing the data in two overlapping sections (-16100 to 1800) and (1760-2003).
The smoothing was done by fitting locally weighted least squares (LOESS) regression curves (Cleveland 1979) with a span of 0.1 and 0.4 for the first and second section, respectively.

References
Cleveland WS (1979) Robust locally weighted regression and smoothing scatterplots. Journal of the American Statistical Association 74:829-836

Contact: https://www.juanpedroferrio.com/