New research reveals why and when the Sahara Desert was periodically green over the past 800,000 years

We still now so little about our climate! Climate models are junk (except for the one used for this study 😉)!

Yes, the climate is always changing and not exactly because of humans!

Unfortunately, the researchers don't say when it will happen the next time again!

"... There is widespread evidence that the Sahara was periodically vegetated in the past, with the proliferation of rivers, lakes and water-dependent animals such as hippos, before it became what is now desert. These North African Humid Periods may have been crucial in providing vegetated corridors out of Africa, allowing the dispersal of various species, including early humans, around the world. ...

The results confirm the North African Humid Periods occurred every 21,000 years and were determined by changes in Earth's orbital precession. This caused warmer summers in the Northern Hemisphere, which intensified the strength of the West African Monsoon system and increased Saharan precipitation, resulting in the spread of savannah-type vegetation across the desert. ..."

From the abstract:

"The Sahara region has experienced periodic wet periods over the Quaternary and beyond. These North African Humid Periods (NAHPs) are astronomically paced by precession which controls the intensity of the African monsoon system. However, most climate models cannot reconcile the magnitude of these events and so the driving mechanisms remain poorly constrained. Here, we utilise a recently developed version of the HadCM3B coupled climate model that simulates 20 NAHPs over the past 800 kyr which have good agreement with NAHPs identified in proxy data. Our results show that precession determines NAHP pacing, but we identify that their amplitude is strongly linked to eccentricity via its control over ice sheet extent. During glacial periods, enhanced ice-albedo driven cooling suppresses NAHP amplitude at precession minima, when humid conditions would otherwise be expected. This highlights the importance of both precession and eccentricity, and the role of high latitude processes in determining the timing and amplitude of the NAHPs. This may have implications for the out of Africa dispersal of plants and animals throughout the Quaternary."

New research reveals why and when the Sahara Desert was green (Secondary source)

New research reveals why and when the Sahara Desert was green (Main source, University of Bristol)  A pioneering study has shed new light on North African humid periods that have occurred over the past 800,000 years and explains why the Sahara Desert was periodically green.

North African humid periods over the past 800,000 years (open access)

Fig. 3: Vegetation reconstructions during composite periods of precession maxima (PMax) and the 20 modelled North African Humid Periods.

Changes of vegetation between humid and arid phases in North Africa. Vegetation zones are based on the minimum precipitation requirements of each vegetation type.