Questions about the absorption and release of carbon due to natural biogeochemical processes, and human interactions with the carbon cycle.
The carbon cycle is the biogeochemical cycle which transports carbon around the earth. This is mediated by a range of different processes which result in the uptake, release, and storage of carbon in different chemical states.
There is a good introduction on the NASA Earth Observatory webpage
Questions with this tag may be about specific processes and fluxes within the carbon cycle (though other more specialised tags may be more appropriate in some cases) - or about how human activities change the direction, magnitude, and rate of processes.