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/

此为自公元前16100年至公元2010年期间大气CO2中d13C值的平滑曲线，该曲线基于南极冰芯数据（Eyer & Leuenberger，个人通信；Francey等，1999；Indermühle等，1999；Leuenberger等，1992）以及来自两个南极站（哈利湾和帕默站）的NOAA ESRL碳循环合作全球空气采样网络的数据瓶。如需使用插值曲线，请务必参照以下内容：

1) NOAA ESRL碳循环合作全球空气采样网络：https://gml.noaa.gov/aftp/data/trace_gases/co2c13/flask/README_surface_flask_co2c13.html

2) 插值曲线的原始出版物：Ferrio JP，Araus JL，Buxó R，Voltas J，Bort J（2005）古农业的水管理实践与气候：从考古植物遗存中的稳定同位素组成推断。植被历史与考古植物学14：510-517

此外，请引用冰芯数据的原始参考文献：

Francey RJ，Allison CE，Etheridge DM，Trudinger CM，Enting IG，Leuenberger M，Langenfelds RL，Michel E，Steele LP（1999）大气CO2中δC-13的1000年高精度记录。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）基于南极泰勒冰川冰芯中捕获的CO2的全新世碳循环动力学。自然398：121-126

Leuenberger M，Siegenthaler U，Langway CC（1992）南极冰芯中最后冰河时期大气CO2的碳同位素组成。自然357：488-490

重要提示：本数据集仅应用于应用插值曲线，例如作为考古植物学、木炭或树木年轮中d13C的参考。应从原始来源检索（并引用）冰芯和NOAA ESRL的原始值。

请记住，这是一个近似值：

1）冰芯数据，尤其是关于捕获的CO2，存在相当大的年代误差。

2）数据仅基于南极冰芯。预计CO2存在相当大的空间变异性。

方法：由于过去两个世纪可获得的时间分辨率较高，因此将数据分为两个重叠部分（-16100至1800）和（1760-2003）进行平滑处理。通过拟合局部加权最小二乘回归曲线（LOESS，Cleveland 1979）进行平滑，第一部分和第二部分的跨度分别为0.1和0.4。

参考文献
Cleveland WS（1979）稳健的局部加权回归和散点图平滑。美国统计学会会刊74：829-836

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