Why is there more carbon coming into the carbon cycle than leaving it?
Actually, present modeling of the carbon cycle indicates that there is an imbalance in the cycle. We are missing over 2 billion tons of carbon each year that we cannot account for. This carbon is being absorbed by some part of the planet that we have not been able to identify. I quote:”Given this analysis we find that there is an imbalance — we need an additional “sink” of -2.2 (3 – 5.2) x1015 g C to balance the global C budget. In other words, we are “missing” over 2 billion tons of C each year; this shows how incomplete our understanding of the global carbon cycle is at present. Although it is possible that this missing sink could be found in any of the major pools of carbon on earth, it is most likely that the pools with a shorter residence time such as vegetation, soils or the ocean (compared to rocks) are most important. Recent models indicate that terrestrial ecosystems are the most likely repository of this carbon.” From :
