An article in National Geographic News reports that there is evidence in satellite imagery that the Sahara, specifically the Sahel, is becoming greener.
A study in 2003 which analyzed NOAA/NASA Pathfinder AVHRR NDVI data found a strong increase in seasonal NDVI (normalized difference vegetative index) over large areas in the Sahel during the period 1982–1999.
A study in 2005 of NOAA-AVHRR NDVI data generated a 23-year time series. The time series analysis revealed two periods (a) 1982–1993 of below average NDVI and (b) 1994–2003 with region-wide above normal NDVI. These patterns agree with recent region-wide trends in Sahel rainfall.
Rainfall in the Sahel has generally increased in recent times, but the strong trend of increasing vegetation cover can only partly be explained by rainfall increase.
A green Sahara is not unprecedented. There is an “overall consensus” that 6 to 9 thousand years ago the Sahara was much greener than today. (Image NASA Worldwind)

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