Forrest fires, volcanic activity, etc.,  ever wonder how much CO2 they put out in the atmosphere alone? Earth is one heck of a controller of the climate, far more than man ever was! We have underwater volcanoes and heat production activity as well.

I was reading on natural nuclear reactors that occurred in nature ions ago no one ever kmew because it was only a theory till the sites were found. Fascinating how the earth has so many things we've yet to really know effect our world.