Fair point, but what if the desert starts greening again? I don't expect it to, but having what nutrients there are NOT blow away would be a start right?
It would definitely have an incredible effect on the climate if you could magically make Africa into a Forest again though. Might even make some parts of Europe uninhabitable with that cooling alone. Not gonna happen though.
photosynthesis efficiency goes up as CO2 increases, and plants need way less water.
This leads to greening of the entire planet and reversing desertification.