Web, I think we are talking past each other. That annual breathing cycle of CO2 is fairly complex. The winter early spring is mainly southern ocean warming causing outgassing with the summer early fall a combination of biological and outgassing in the northern hemisphere. The southern hemisphere in NH summer has more thermal CO2 uptake, the NH more biological annual sequestering. The variation in tropical ocean temperature is rather small except for the ENSO changes (multi-year) which are barely discernible in the CO2 measurements.
Even the paper your referenced shows more NH fluctuation, then SH and finally tropics, just like the satellite animation of atmospheric CO2.
I disagree with Bartimes that it is all temperature, but there is a significant amount related to temperature change, both biological and outgassing. The feedback thing is kinda interesting though. CO2 should tend to stabilize the lower troposphere as its impact increases (isothermal is pretty stable, that is where things would be headed.) The actual trend is toward more instability. that is like approaching a bifurcation point. Sea surface temperatures are becoming more volatile regionally, yet the average is stabilizing with some small reduction.
With the Arctic ozone depletion starting and some indication of tropical ozone reduction (remember the stratosphere is marching to a different drummer), there is likely to be some neat atmospheric chemistry starting. Ice clouds react with ozone allowing CO2 to find a reaction buddy, kinda like Mars. There is a slight inverse correlation of CO2 variation with solar. This is getting kinda interesting.