The concentration of atmospheric carbon dioxide at Baring Head, New Zealand

The concentration of atmospheric CO₂ has been measured at Baring Head, near Wellington, New Zealand, since December 1972. In the period January 1973 to January 1977, the CO₂ concentration was observed to rise by 4.6 p.p.m. Superimposed on the long-term increase was a seasonal oscillation with an amplitude of 1.1 p.p.m. having a maximum in October and a minimum in April. The oscillation was in phase with, and of nearly the same amplitude as, the seasonal oscillation observed at the South Pole. The mean CO₂ concentrations at Baring Head and the South Pole over the period January 1973 to January 1977, were almost the same, each being about 2 p.p.m. lower than at Mauna Loa in Hawaii for the same period.

The problem of intercomparison between different atmospheric CO₂ monitoring stations has been minimized by chemical analyses of all reference gases used at the stations. The reference gases were analysed both before and after use at the field stations by a single calibration laboratory at Scripps Institution of Oceanography.