Atmospheric Carbon Dioxide Record from Mauna Loa, Hawaii, USA

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

June 1991 - December 2006

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).

Manua Loa, Hawaii, USA
19°32' N, 155°35' W, 3397m above MSL

Trends

These measurements indicate a rise in annual average atmospheric CO₂ concentration from 356.65 parts per million by volume (ppmv) in 1992 to 381.74 ppmv in 2006, or an increase of about 1.79 ppmv/year, on average. These data may be compared with flask samples taken by the National Oceanic and Atmospheric Administration (NOAA), Geophysical Monitoring Division (GMD), which show an increase from 356.58 ppmv in 1992 to 381.88 ppmv in 2006, or an average increase of about 1.81 ppmv/year. Another possible comparison is with continuous measurements made through 2004 by the Scripps Institution of Oceanography; these data are also available in TRENDS. The Scripps data show an increase from 356.37 ppmv in 1992 to 377.38 ppmv in 2004, or an increase of 1.75 ppmv/year. The corresponding (1992-2004)average change for these CSIRO flask data is 1.73 ppmv/year. Differences are partly due to different sampling methods; the CSIRO (flask) data are taken at particular times, while the Scripps and NOAA/CMDL data represent continuous measurements. There are also differences in statistical treatment of the data (e.g., acceptance criteria, smoothing techniques), as well as instrument differences which are discussed by Masarie et al. (2001).

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 Meteorological 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.
• Masarie, K.A., R.L. Langenfelds, C.E. Allison, T.J. Conway, E.J. Dlugokencky, R.J. Francey, P.C. Novelli, L.P. Steele, P.P. Tans, B. Vaughn, and J.W.C. White. 2001. NOAA/CSIRO Flask Air Intercomparison Experiment: A strategy for directly assessing consistency among atmospheric measurements made by independent laboratories, J. Geophys. Res., 106, 20445-20464.
• 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