I cannot get too bogged down in this dispute, jake, as my previous experience tells me that it goes on ad infinitum.
However, I don't think it is argued that about 96% of emissions are from "natural" activities and the other 4% from human activities (though I would argue that human activity is natural as well, but no matter).
It seems from the arguments that are around that the earth can cope with variations in the 96% because they are somehow "absorbed", but it cannot cope with variations in the 4% because they are somehow not absorbed. If I have this right in my mind the earth's absorption mechanism is extremely cute in that it can discriminate between the two types of emissions.
It is clear that a small variation in the 96% will be far greater in absolute terms than a large variation in the 4%. But then I’m just a simple lad, and cannot understand how the variations in one type of emission (much larger in absolute terms) can be handled, but variations in the other (much smaller in absolute terms) cannot.