No, it wasn’t always arid. The Sahara was once wet and green, and among others, it had hippos. Scientists seek to know exactly how and when it happened. It could teach us more about humanity’s expansion across the planet.
Our planet has changed a lot over billions of years. Researchers from Finland and the United Kingdom reconstructed the periodic transformations of the Sahara. They tracked it back over 800,000 years using a new climate model.
They focused especially on the so-called African wet periods. These are periods when the African continent was much wetter and greener than today. The climate model was used to investigate the timing and driving forces of these periods.
The model incorporates improvements regarding atmospheric convection and vegetation propagation. This filled gaps in what we know about the history of the Saharan region. «It is one of the most notable environmental changes on the planet. “It is about the cyclical transformation of the Sahara desert into savanna and forest ecosystems.” This is stated by climatologist Edward Armstrong, from the University of Helsinki, Finland.
The study simulates African wet periods with a magnitude comparable to that indicated by paleoclimatic observations. Reveal why and when these events occurred. An old hypothesis was corroborated. African wet periods are driven by the Earth’s orbital precession, the way it wobbles on its axis over a 21,000-year cycle. It affects the variation between the four seasons and the strength of the African monsoon weather system.
The precessions would have meant warmer summers in the Northern Hemisphere. Also, more intense monsoons in West Africa and, therefore, more precipitation in the Sahara.
The Sahara was humid and green, without a doubt. It is very possible that these periods of greenery modified the movements of man and other species. They traveled through areas of the Sahara that were normally very difficult to cross. “Our ability to model wet periods in North Africa is a great achievement. “We can model human distributions and understand the evolution of our genus in Africa.” This is how Miikka Tallavaara, a geoscientist at the University of Helsinki, concludes.