Surely dissolving CO2 in the ocean acts as a buffer, not a sink? We will have to stop emitting all of that CO2 as well (and future generations will have to sequester it). The net absorption / emission from the biosphere involves a lot of emission following from our changes to the planet. We can significantly reduce our emissions (and slowly recover some of them) with better stewardship of the environment but there is a risk to the sequestered carbon: eg. where climate change causes forests to die and release most of their stored carbon.