When you actually look at the carbon cycle model, with all the compartments and flows, you notice that putting carbon into the soil could actually offset all the fossil fuel burning and more. If we did that to the extent that the soil had before we farmed it to death, CO2 movement into the atmosphere would turn negative. Of course, once we got the soil saturated with carbon, it would rise again but maybe no faster than movement from the atmosphere into the ocean would handle.