[incrudible]

This is an oversimplification. If it just stayed in the atmosphere indefinitely after emission, then the rate of increase in CO2 concentration should match the rate of increase of CO2 emission. In reality, this just isn't the case, because an increase in CO2 concentration leads to an increase in uptake on the surface. This increased uptake may well be a negative in some ways (ocean acidifaction), but it may also be a positive in other ways (agricultural yields).