AndyTheBear,
I kind of think that the more global warming, the more topography expands, the more plant life expands and of course animal life. The two cycles, carbon and nitrate work together as the topography moves north and south as the earth cools and warms.
Well, I am no expert here, and I gladly welcome better information, but as I understand it there is some carbon that is out of service of such cycles...or at the least that is part of much longer cycles. For example carbon that sinks so deeply in the ocean that it leaves the life cycle for some extended and difficult to predict amount of time or carbon that becomes buried deeply enough in the ground that plant roots don't capture it.
I got this idea from a handy graphic of "carbon cycles" someone presented to me once...but I can not vouch for the veracity of the graphic.