Abstract
We analyzed temporal variations of the latitudinal distribution of the annual mean CO2 in the upper troposphere (about 10km) based on the long record of JAL airliner observations between Japan and Australia over the period 1995-2008, combined with the earlier data in 1984 and 1985. We found long-term increasing trends of the CO2 gradients in the most northern latitudes as fossil fuel emissions have increased year by year. Linear regressions of the CO2 gradients versus global fossil-fuel emissions give a largest positive slope at 30N-25N, but a small negative slope around the southern tropics. Back extrapolations of the CO2 gradient trends to zero fossil fuel emissions showed a negative north-south gradient with the Northern Hemisphere lower than the Southern, as well as a regional CO2 increase in the tropical regions.
