| Abstract: The difference between Mauna Loa and South Pole atmospheric CO2
concentrations from 1959 to the present scales linearly with CO2
emissions from fossil fuel burning and cement production (together called fossil CO2). An extrapolation to zero fossil CO2
emission has been used to suggest that the atmospheric CO2
concentration at Mauna Loa was 0.8 ppm less than that at the South Pole before the industrial revolution, associated with a northward atmospheric transport of about 1 Gt C yr-1 (Keeling et al., 1989a). Mass conservation requires an equal southward transport in the ocean. However, our ocean general circulation and biogeochemistry model predicts a much smaller pre-industrial carbon transport. Here, we present a new analysis of the Mauna Loa and South Pole CO2data, using a general circulation model and a 2-box model of the atmosphere. It is suggested that the present CO2
difference between Mauna Loa and the South Pole is caused by, in addition to fossil CO2
sources and sinks, a pre-industrial interhemispheric flux of 0.5-0.7 Gt C yr-1 ,
and a terrestrial sink of 0.8-1.2 Gt C yr-1
in the mid-latitude Northern Hemisphere, balanced by a tropical deforestation source that has been operating continuously in the period from 1959 to the present. |