TRENDS: ATMOSPHERIC CARBON DIOXIDE

Atmospheric carbon dioxide record from continuous in situ measurements at Mauna Loa, Hawaii

Graphics

Digital Data

K.W. Thoning and P.P. Tans

National Oceanic and Atmospheric Administration, Climate Monitoring and Diagnostics Laboratory, Boulder, Colorado 80303, U.S.A

Period of Record

1974-98

Methods

A URAS-2 nondispersive infrared CO₂ analyzer (NDIR) manufactured by Hartmann and Braun was used from the start of the continuous NOAA/CMDL measurements at Mauna Loa until August 1987. Since then a Siemens ULTRAMAT 3 CO₂ analyzer has been used.

Details on the sampling methods, NDIR apparatus, and calibration standards are provided in Komhyr et al. (1983), Thoning et al. (1987, 1995), and Zhang et al. (1997).

Data selection steps include an hour-to-hour difference criterion that rejects data that change by more than 0.25 parts per million by volume (ppmv) from one hour to the next. For data from 1983 to present, a third selection step based on residuals from a spline fit (Thoning 1989) is applied.

Mauna Loa, Hawaii, U.S.A.
Barren volcanic slope
19°32' N, 155°35'W
3397 m above MSL

Trends

According to this continuous CO₂ record, since 1976 the annual CO₂ concentration at Mauna Loa has risen from 332.04 parts per million by volume (ppmv) to 366.49 ppmv in 1998. Thoning et al. (1989) reported the amplitude of the seasonal cycle at Mauna Loa to be growing at 0.05 ± 0.02 ppm yr^-1 and the annual growth rate to be 1.42 ± 0.02 ppm/year for 1974-85. For comparison to the CMDL flask CO₂ data, Conway et al. (1988) reported a growth rate of 1.21 ppmv yr^-1 for Mauna Loa from 1981-84 and a global growth rate of 1.43 ppm yr^-1 for 1981-92 (Conway et al. 1994). Thoning et al. (1989) also compared the Mauna Loa continuous CO₂ data with the CO₂ flask sample data from the sea level site at Cape Kumukahi, Hawaii, and found the seasonal cycle at Cape Kumukahi was 23% larger than the seasonal cycle at Mauna Loa, with the phase of the cycle at Mauna Loa lagging the cycle at Cape Kumukahi by about 1-2 weeks.

References

Conway, T.J., P. Tans, L.S. Waterman, K.W. Thoning, K.A. Masarie, and R.H. Gammon. 1988.

Atmospheric carbon dioxide measurements in the remote global troposphere, 1981-84. Tellus 40(B):81-115.

Conway, T.J., P.P. Tans, L.S. Waterman, K.W. Thoning, D.R. Kitzis, K.A. Masarie, and N. Zhang. 1994.

Evidence for interannual variability of the carbon cycle from the National Oceanic and Atmospheric Administration/Climate Monitoring and Diagnostics Laboratory Global Air Sampling Network. Journal of Geophysical Research 99(D11):22831-55.

Komhyr, W.D., T.B. Harris, and L.S. Waterman, J.F.S. Chin, and K.W. Thoning. 1989.

Atmospheric carbon dioxide at Mauna Loa Observatory 1. NOAA Global Monitoring for Climate Change measurements with a nondispersive infrared analyzer, 1974-85. Journal of Geophysical Research 94(D6):8533-47.

Komhyr, W.D., L.S. Waterman, and W.R. Taylor. 1983.

Semiautomatic nondispersive infrared analyzer apparatus for CO₂ air sample analyses. Journal of Geophysical Research 88:1315-22.

Thoning, K.W. 1989.

Selection of NOAA/GMCC CO₂ data from Mauna Loa Observatory. In W.P. Elliot (ed.), The Statistical Treatment of CO₂ Data Records. NOAA Technical Memorandum ERL ARL-173. Air Resources Laboratory, Silver Spring, Maryland.

Thoning, K.W., P. Tans, T.J. Conway, and L.S. Waterman. 1987.

NOAA/GMCC calibrations of CO₂-in-air reference gases: 1979-85. NOAA Technical Memorandum ERL ARL-150. Environmental Research Laboratory, Boulder, Colorado.

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, 1974-85. Journal of Geophysical Research 94(D6):8549-65.

Thoning, K.W., T.J. Conway, N. Zhang, and D. Kitzis. 1995.

Analysis system for measurement of CO₂ mixing ratios in flask air samples. Journal of Atmospheric and Oceanic Technology 12(6):1349-56.

Zhang, N., P.P. Tans, and K.W. Thoning. 1997.

A high precision manometric system for absolute calibrations of CO₂ in dry air. Journal of Geophysical Research 102(D5):5885-94.

CITE AS: Thoning, K.W. and P.P. Tans. 2000. Atmospheric CO₂ records from sites in the NOAA/CMDL continuous monitoring network. In Trends: A Compendium of Data on Global Change. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A.

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