birdie//The IPCC originally stated that man-made CO2 would take approximately 100 years to dissipate down to background levels (not millennia). That is to say, if all man-made CO2 emissions were to cease tomorrow, their effects would only be felt around 100 years into the future. However, recent studies have reduced this hundred year figure by an order of magnitude. //
Firstly the effects of the carbon already in the atmosphere will cause the temperature to continue increasing for another forty years due to the thermal inertia of the oceans.
The time it would take to get carbon dioxide levels back to preindustrial levels has not been clearly determined. The ocean will continue to absorb it from the atmosphere but the rate of removal will decease when the ocean temperature rises.
However the carbon dioxide will continue to acidify the oceans (causing havoc for the marine ecosystems) for a very long time because the process of geological sequestration is very slow. Yes millennia.
It certainly won't clear it out "an order of magnitude faster", in a decade.
In any case, emissions won't stop tomorrow. The rate of carbon release still continue to increase every year. If we don't start working on the problem we will have huge problem. And whatever time it takes for the carbon levels to fall, it will definitely be longer, the higher the concentration we reach.