Warmair; you and Bugsy seem to think the AF is automatically equal to the increase in atmospheric CO2 because natural sinks and emissions are in balance and therefore any increase is due to the unnatural ACO2 emissions. That would explain you saying this:

“This suggests that AF could reach a 100% If not why not ?”

A 100% of what?

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100% of man's Co2 emissions . In other words AF goes from 40% to 100%

If CO2 levels rise by say 12 PPM for every 1 deg increase of temperature (as per your link) then I am happy to concede that the increase in temperature may be directly responsible for total of 8.4 ppm (0.7X12) over the last 150 years. The problem is that nature is either a net emitter or a net absorber. In a world without man made Co2 for levels to rise in the atmosphere it means nature has to be a net emitter which leaves no place for man made Co2 go except to accumulate in the atmosphere. In other words 100% of man's emissions of Co2 must remain in the atmosphere and the airborne fraction hits 100%. Can you explain what is wrong with that idea ?

Land based sinks are increasing; the "Normalized Difference Vegetation Index" (NDVI)confirms this; literally there are more plants and denser growth; this is why I think the Canadell LUC figure is problematic.

As well oceans can be both an emitter via the increase in temperature and a sink via the growth of cynaobacteria which have increased in recent years;

http://wattsupwiththat.com/2011/04/25/the-ocean-wins-again/#more-38673

nature is not simple and AGW is based on a simple nature.

I am sooo tempted to say something about simple natures...

but I won't.

Seriously, the LUC figure may be problematic, but that is beside the point, you cannot ignore it and then use Knorrs 40% AF without factoring it in, because he factored it in when calculating the AF.

Your last post makes you sound confused cohenite. Somehow land sinks are increasing, but the oceans can be a bit one way or the other, a litany of "we don't know for sure, I'll ignore it then". But of course somewhere is belching out huge wads of CO2 that totally eclipses what we are adding, and it's not going back in. That we know for sure, right? But can't be phytoplankton or cyanobacteria or whatever, right? Or land use, right? What then? What is delivering such massive amounts of CO2 that noone has noticed.

Give us a call when you figure it out.