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ABOUT MAUNA LOA CARBON DIOXIDE 1974-1985

Data on the carbon dioxide (CO2) content of the atmosphere at the Mauna Loa Observatory on the Big Island of Hawaii have been measured nearly continuously since the 1950s. A portion of the data are given here, from 1974-1985. Time is expressed in months, with May of 1974 as month 1 (zero was not used to avoid the usual problems with exponential and power law regression). The observatory is at 3,400 m or 11,000 feet above sea level.

The data show both a cyclic behavior and a linear trend. The cyclic behavior corresponds to a yearly cycle of increasing atmospheric CO2 from late fall to spring, with a maximum in May, and then decreasing atmospheric CO2 from spring to late fall, with a minimum in October. The simple interpretation is that carbon dioxide is "scrubbed" or removed from the northern hemisphere atmosphere during the spring-summer growing cycle, when green plants suck up CO2 during photosynthesis. Carbon dioxide is then released during fall and winter, when plants die and rot.

The linear increase of mean yearly atmospheric CO2 with time is actually an exponential increase of mean yearly atmospheric CO2 as measured over a longer time scale beginning in the late 1950s. The yearly increase appears linear because of the short time scale selected for this data set. Fossil fuel consumption appears to be the prime source of this secular increase, with occasional oceanic contributions due to changes in sea surface temperatures associated with currents like El Nino. To see the lastest long-term data, including interpolations for missing values, go to DataSet #078.

Students could find the linear regression for this data set, then subtract that linear increase from the actual data to isolate the cyclic behavior. The cyclic data could then be modelled with simple sinusoidal functions. Notice that there is a "knee" in every yearly cycle from January to December when carbon dioxide concentration does not increase as fast as one might expect. The residuals from the sinusoidal model might prove interesting.

Reference: Komhyr, W. D., Harris, T. B., Waterman, L. S., Chin, J. F. S. and Thoning, K. W. (1989), Atmospheric carbon dioxide at Mauna Loa Observatory 1. NOAA Global monitoring for climatic change measurements with a nondispersive infrared analyzer, 1974-1985; J. Geop. Res., v. 94, no. D6, pp. 8533-8547.

Thoning et al (1989), "2"; JGR v. 94, pp.

Keeling et al (1976), Tellus v. 28, pp. 538-551.

Martin and Diaz (1991), JGR v. 96, pp. 18689-18704.

Rust etal (1979), JGR v. 84, pp. 3115-3122,

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View the Data

 Data from Komhyr et al (1989) monthly mean CO2 mole fractions from Mauna Loa Observatory values in ppm month (num.) CO2 (ppm) 1 333.15 2 332.07 3 330.99 4 329.17 5 327.39 6 327.25 7 328.50 8 329.51 9 330.69 10 331.41 11 331.84 12 333.26 13 333.92 14 333.39 15 331.81 16 329.90 17 328.56 18 328.45 19 329.29 20 21 331.65 22 332.66 23 333.53 24 334.80 25 334.80 26 334.14 27 332.88 28 330.64 29 329.01 30 328.62 31 330.13 32 331.63 33 332.74 34 333.23 35 334.91 36 336.01 37 336.82 38 336.13 39 334.75 40 332.53 41 331.27 42 331.21 43 332.36 44 333.47 45 334.74 46 335.22 47 336.52 48 337.77 49 338.00 50 338.04 51 336.39 52 334.33 53 332.35 54 332.33 55 333.77 56 334.80 57 336.20 58 336.65 59 337.79 60 338.95 61 339.03 62 339.22 63 337.58 64 335.51 65 333.83 66 334.05 67 335.26 68 336.70 69 337.81 70 338.26 71 340.07 72 340.87 73 341.48 74 341.30 75 339.36 76 337.84 77 335.98 78 336.07 79 337.22 80 338.33 81 339.35 82 340.47 83 341.73 84 342.47 85 343.02 86 342.46 87 340.78 88 338.61 89 337.04 90 337.13 91 338.49 92 339.85 93 340.93 94 341.67 95 342.78 96 343.71 97 344.31 98 343.41 99 341.96 100 339.79 101 337.91 102 338.10 103 339.27 104 340.67 105 341.45 106 342.69 107 343.21 108 345.17 109 345.79 110 345.40 111 343.99 112 342.00 113 340.02 114 340.16 115 341.39 116 343.01 117 343.92 118 344.64 119 345.18 120 347.10 121 347.45 122 346.80 123 345.44 124 343.24 125 341.25 126 341.49 127 342.84 128 344.37 129 345.03 130 345.89 131 347.47 132 348.02 133 348.73 134 348.11 135 346.59 136 344.59 137 343.01 138 342.88 139 344.19 140 345.64

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