Analysis of a 39-year continuous atmospheric CO₂ record from Baring Head, New Zealand

Interannual variations in CO₂ growth rate in the Baring Head record closely match the El Niño-Southern Oscillation, reflecting the global reach of CO₂ mole fraction anomalies associated with this cycle. We use atmospheric transport model results to investigate contributions to seasonal and annual-mean components of the observed CO₂ record. Long-term trends in mean gradients between Baring Head and other stations are predominately due to increases in Northern Hemisphere fossil-fuel burning and Southern Ocean CO₂ uptake, for which there remains a wide range of future estimates.

We find that the postulated recent reduction in the efficiency of Southern Ocean anthropogenic CO₂ uptake, as a result of increased zonal winds, is too small to be detectable as significant differences in atmospheric CO₂ between mid to high latitude Southern Hemisphere observing stations.