Scientists Reveal the Impact of Earth’s Orbital Changes on the Greening of the Sahara
Algeria’s Tassili N’Ajjer plateau contains a vast collection of rock art that provides a unique record of the Sahara’s past environmental conditions. The ancient paintings and etchings, some dating back as much as 11,000 years, depict a vibrant, green landscape teeming with wildlife, a stark contrast to the arid desert that exists there today. These images offer valuable insights into a period called the Green Sahara or North African Humid Period, which occurred approximately 6,000–11,000 years ago.
The greening of the Sahara is a phenomenon that has puzzled scientists for many years. Researchers have now identified that the recurring greening events were driven by changes in the Earth’s orbital precession—the slight wobbling of the planet while rotating. This movement influenced the distribution of rainfall in the Sahara, resulting in the expansion of savannah and wooded grassland across the desert.
A team of climate modelers and anthropologists developed a climate model that accurately simulates atmospheric circulation over the Sahara and the impacts of vegetation on rainfall. Their study revealed that warmer Northern Hemisphere summers, caused by changes in Earth’s orbital precession, intensified the strength of the West African Monsoon system and shifted the African rainbelt northwards, leading to increased Saharan rainfall.
Furthermore, the study found that the alternating humid and arid phases in the Sahara had significant consequences for the dispersal and evolution of species, including humans. It also provides important insights into how future climate warming may influence rainfall and vegetation in the Sahara region and the wider implications for society.
The researchers’ ability to model the African humid periods offers valuable knowledge for understanding the impact of future climate change on the Sahara and its implications for the environment and human society.
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