How could global warming accelerate if CO2 is 'logarithmic'?

"In summary:

Although CO2 has less effect at higher CO2 concentrations, this "logarithmic effect" will be overpowered by these 4 factors if we don't switch to clean energy quickly:

* Exponential growth of energy use

* Past CO2 emissions that nature has not yet absorbed

* Carbon sink saturation

* Committed warming"