Atmospheric Carbon Dioxide Record from Shetland Islands, Scotland

Graphics    Digital Data

Investigators

L.P. Steele, P.B. Krummel and R.L. Langenfelds
Commonwealth Scientific and Industrial Research Organization (CSIRO),
Atmospheric Research,
Aspendale, Victoria, Australia, 3195

Period of Record

December 1992 - November 2003

Methods

Individual measurements have been obtained from flask air samples returned to the CSIRO GASLAB. Typical sample storage times range from days to weeks for some sites (e.g. Cape Grim, Aircraft over Tasmania and Bass Strait) to as much as one year for Macquarie Island and the Antarctic sites. Experiments carried out to test for changes in sample CO₂ mixing ratio during storage have shown significant drifts in some flask types over test periods of several months to years (Cooper et al., 1999). Corrections derived from the test results are applied to network data according to flask type.

Samples were analysed by gas chromatography with flame ionization detection after methanization of CO₂ to CH₄. One Carle gas chromatograph, labeled "Carle-3" (C3) was used over the length of the record. Further details of CSIRO's global sampling network, sampling procedure, and analytical techniques are provided elsewhere (e.g., Francey et al., 1996); measurement uncertainty is discussed by Langenfelds et al. (2001).

Data are reported in the WMO CO₂ Mole Fraction Scale. The link to this scale was established with nine 'primary' high-pressure cylinder standards of synthetic mixtures of CO₂ and CO in "zero air" (hydrocarbon-free air) calibrated by NOAA/CMDL in 1992, with a subset recalibrated in 1994. The relative stability of the primary suite is monitored using frequent comparisons with about 15 long-lived secondary standards. The link to the international scale is monitored by a variety of on-going comparisons involving high-pressure cylinder standards (e.g., WMO Round Robins, IAEA CLASSIC, cylinder exchanges with NOAA, etc.), as well as 6-per-month flask-air-sharing comparisons of samples collected at Cape Grim. More detailed calibration information is given by Langenfelds et al. (2001).

These data represent monthly means, calculated as the mean of daily values from a smooth curve fit to the data using the curve-fitting routines described by Thoning et al. (1989).

Shetland Islands, Scotland
60°10' N, 01°10' W, 30m above MSL

Trends

These measurements indicate a rise in annual average atmospheric CO₂ concentration from 356.89 parts per million by volume (ppmv) in 1993 to 372.34 ppmv in 2002, or an increase of 1.72 ppmv/year, on average. This average increase is somewhat higher than that shown in records extending back to 1992, reflecting a particularly small increase from 1992-1993.

References

• Cooper, L.N., L.P. Steele, R.L. Langenfelds, D.A. Spencer, and M.P. Lucarelli. 1999. Atmospheric methane, carbon dioxide, hydrogen, carbon monoxide and nitrous oxide from Cape Grim flask air samples analysed by gas chromatography. Baseline Atmospheric Program (Australia) 1996, edited by J.L. Gras, N. Derek, N.W. Tindale, and A.L. Dick, pp. 98-102, Bureau of Meteorology and CSIRO Atmospheric Research, Melbourne, Australia.
• Francey, R.J., L.P. Steele, R.L. Langenfelds, M.P. Lucarelli, C.E. Allison, D.J. Beardsmore, S.A. Coram, N. Derek, F.R. de Silva, D.M. Etheridge, P.J. Fraser, R.J. Henry, B. Turner, E.D. Welch, D.A. Spencer, and L.N. Cooper. 1996. Global Atmospheric Sampling Laboratory (GASLAB): supporting and extending the Cape Grim trace gas programs. Baseline Atmospheric Program (Australia) 1993, edited by R.J. Francey, A.L. Dick, and N. Derek, pp. 8-29, Bureau of Meteorology and CSIRO Division of Atmospheric Research, Melbourne, Australia.
• Francey, R.J., L.P. Steele, D.A. Spencer, R.L. Langenfelds, R.M. Law, P.B. Krummel, P.J. Fraser, D.M. Etheridge, N.Derek, S.A. Coram, L.N. Cooper, C.E. Allison, L.Porter and S.Baly. 2003. The CSIRO (Australia) measurement of greenhouse gases in the global atmosphere,report of the 11th WMO/IAEA Meeting of Experts on Carbon Dioxide Concentration and Related Tracer Measurement Techniques,Tokyo, Japan, September 2001, S.Toru and S.Kazuto (editors), World Meterological Organization Global Atmosphere Watch, 97-111.
• Langenfelds, R.L., L.P. Steele, C.E. Allison, and R.J. Francey. 2001. GASLAB Calibration Information, Internal Report, CSIRO Atmospheric Research, Aspendale, Australia.
• Thoning, K.W., P.P. Tans, and W.D. Komhyr. 1989. Atmospheric carbon dioxide at Mauna Loa Observatory, 2, Analysis of the NOAA/GMCC data, 1974 - 1985, J. Geophys. Res., 94, 8549-8565.

December 2007