AFAIK this was done simply by assuming the change of the color, without taking into account the change of cloud coverage, and clouds have a huge effect. So it can go both ways depending on how exactly we will be changing the climate of Sahara.
And there are many possible ways to control the climate in a smart way instead of trying to simply remove CO2. One possibility is to use ocean thermal energy conversion plants [1], to cool down tropical region of northern hemisphere, artificially re-creating conditions that cause green Sahara periodically. Aubrey de Greys new moonshot https://viento.ai/ is working on similar ideas.
And there are many possible ways to control the climate in a smart way instead of trying to simply remove CO2. One possibility is to use ocean thermal energy conversion plants [1], to cool down tropical region of northern hemisphere, artificially re-creating conditions that cause green Sahara periodically. Aubrey de Greys new moonshot https://viento.ai/ is working on similar ideas.
[1] https://en.wikipedia.org/wiki/Ocean_thermal_energy_conversio...