More than 100% of human CO2 must be removed.
From Environmental Research Web:
With a middle-of-the-road scenario for carbon dioxide removal, however, a 20th century-like climate could be restored by the late 24th or early 25th century, MacDougall found. But simulated surface air temperature would still be above the pre-industrial temperature by the end of the 30th century, even for the fastest carbon removal scenario he modelled, as oceans gradually release their stored heat.
Restoring climate will require removal of more carbon from the atmosphere than was originally emitted by man, MacDougall said. In some scenarios, 115-190% of anthropogenic emissions will need to be sequestered.