Interesting. But still, aren't the remarkable excursions in CO2 through time (that we can discern anyway) associated with volcanics and major oceanographic reconfigurations? ... I will read the paper though ;)

The correct model is that they are mostly volcanic in origin. But how the system compensates for that is a bit of a question of the net balance of the system. It's not just an issue of weahtering, but also what is eroded and where it ends up.