The earth is a very active planet and has plenty of volcanoes that can do a better job than us of polluting the atmosphere, in fact plants need CO2 to grow so the extra CO2 is doing a fine job of greening the planet and making food grow faster and larger. The real culprit is human overpopulation and no one seems to mention it, all the larger religions encourage their followers to have plenty of kids, as if they are trying to make their religion the largest one, perish the thought
Where there are plenty of trees the CO2 rises in winter but falls in summer as the trees take it in, deforestation put a stop to this natural cycle.
As Seeker says methane is much better ( worse) green house gas than CO2, so if that starts bubbling up we are really in trouble, maybe we should capture and burn it to produce much more friendly CO2....