Of course if the concentration goes down then the forcing would be negative. If you want to make some other graph then go ahead. I was simply showing how the ln graphs were made. They are all similar.

The IPCC estimate for alpha is too high because they are overestimating the effect of CO2 on temperature. They had no other idea of what could be causing global warming, so they subbed in CO2 and blamed us. Their models have falsified. They got it wrong. We are not the cause.