This article of desert greening states that some areas around the Sahara have seen increased plant growth in recent decades, caused by global warming. The causal chain would be warmer air can hold more water -> more precipitation -> more plant growth.
Apparently (from historical sources) the Sahara was wetter during the medieval climate anomaly, which would fit.
However, the article gives as sources satellite images, reports by locals on plant growth and climate models predicting increased precipitation. Which makes me wonder, isn't there direct measurement of precipitation in some relevant areas (over the last decades)? Don't we have direct data to check?
Helpful would be data from the areas indicated in the article: Sahel zone, central Chad, Western Sudan.