With more than 8.5 million square kilometers, the Sahara is the largest desert area on earth. The environment is very poor in fauna, flora, and especially water. The dust is carried by the wind, to land in the Caribbean and in the Amazon. Global warming and greenhouse gases further stretch its surface by several kilometers per year.
The NOAA (National Oceanic and Atmospheric Administration) says that in the past, this sea of sand was a place where grasses and shrubs grew. Kathleen Johnson, a researcher at the University of California, explains this change in climate by a change in the axis of rotation of the earth.
In the distant future, this area occupying the upper third of Africa could naturally revert to its lush and humid past .
An event that occurs regularly
The planet's largest desert hasn't always been as arid as it is today. Oceanic sediments have been analyzed by researchers, proving the existence of vegetation that once covered the Sahara. There were lakes full of fish, as well as large mammals, such as elephants and hippos. The prehistoric paintings in the caves allow to deduce that the man lived there, while raising cattle.
The last time this event happened was a few thousand years ago, between 12,000 and 5,000 years before Jesus Christ. Numerous fossils attest to the ancient presence of marine animals, as well as domestic animals such as oxen. Around the year -3900, the Saharan region becomes arid again, to remain so until today. Scientists estimate that the greenery could come back in ten thousand years.
The reason for the climate change
In parts of this desert expanse, the average precipitation is less than 2 mm per year. To obtain a fairly luxuriant fauna, capable of attracting large pachyderms, it is absolutely necessary to have significant rainfall. Yet this happens roughly every 23,000 years, when the Earth's axis of rotation changes a few degrees.
The change in the tilt of our planet has the effect of increasing the amount of sunshine in the northern hemisphere during the winter months. The result is that the temperature rises and creates an area of low pressure, attracting wet winds from the oceans, especially the monsoon. This axial change, occurring in regular cycles, is caused by the combined forces exerted by the moon and the other planets in the solar system.