What is the residence time of CO2 in the atmosphere?
This is more a question of semantics than of substance. The air, oceans, and biosphere are closely linked. Carbon naturally and quickly flows from one to the other to the other. If you could tag and follow an individual carbon atom from the coal mine to the power plant to the air, it wouldn’t take long for that carbon atom, now part of a CO2 molecule, to end up in the ocean or in a growing leaf. So in that sense, 5 years is about right. But that also means that burning fossil carbon saturates the entire carbon cycle in all three phases. In other words, the fact that the leaf or the ocean took up a fossil carbon atom means that there is another non-fossil carbon atom that *didn’t* get removed from the air, and that will stay in the air longer because of that. And it won’t take long before that leaf dies and is oxidized, or until that oceanic CO2 is respirated back into the air again. So what you really want to know from a climatological perspective is this: if you artificially increase
