Articles | Volume 14, issue 4
Atmos. Meas. Tech., 14, 3015–3032, 2021
Atmos. Meas. Tech., 14, 3015–3032, 2021

Research article 26 Apr 2021

Research article | 26 Apr 2021

Revision of the World Meteorological Organization Global Atmosphere Watch (WMO/GAW) CO2 calibration scale

Bradley D. Hall et al.

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Cited articles

Flores, E., Viallon, J., Choteau, T., Moussay, P., Idrees, F., Wielgosz, R. I., Lee, J., Zalewska, E., Nieuwenkamp, G., Veen, A. v. d., Konopelko, L. A., Kustikov, Y. A., Kolobova, A. V., Chubchenko, Y. K., Efremova, O. V., Zhe, B. I., Zhou, Z., Zhou, Z., Rhoderick, G. C., Hodge, J. T., Shimosaka, T., Aoki, N., Hall, B., Brewer, P., Cieciora, D., Sega, M., Macé, T., Fükő, J., Nagyné Szilágyi, Z., Büki, T., Jozela, M. I., Ntsasa, N. G., Leshabane, N., Tshilongo, J., Johri, P., and Tarhan, T.: CCQM-K120 (Carbon dioxide at background and urban level), Metrologia, 56, 08001,, 2018. 
Hall, B. D., Dutton, G. S., Mondeel, D. J., Nance, J. D., Rigby, M., Butler, J. H., Moore, F. L., Hurst, D. F., and Elkins, J. W.: Improving measurements of SF6 for the study of atmospheric transport and emissions, Atmos. Meas. Tech., 4, 2441–2451,, 2011. 
Hall, B. D., Crotwell, A. M., Miller, B. R., Schibig, M., and Elkins, J. W.: Gravimetrically prepared carbon dioxide standards in support of atmospheric research, Atmos. Meas. Tech., 12, 517–524,, 2019. 
JCGM: Evaluation of Measurement Data – Guide to the Expression of Uncertainty in Measurement (ISO GUM 1995 with minor corrections), Joint Committee for Guides in Metrology, Sèvres, France, 2008. 
Keeling, C. D., Guenther, P. R., and Moss, D. J.: Scripps reference gas calibration system for carbon dioxide-in-air standards: revision of 1985, WMO/TD-No. 125, available at: (last access: 20 April 2021), 1986. 
Short summary
We have recently revised the carbon dioxide calibration scale used by numerous laboratories that measure atmospheric CO2. The revision follows from an improved understanding of the manometric method used to determine the absolute amount of CO2 in an atmospheric air sample. The new scale is 0.18 μmol mol−1 (ppm) greater than the previous scale at 400 ppm CO2. While this difference is small in relative terms (0.045 %), it is significant in terms of atmospheric monitoring.