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Scientists believe the Sahara desert is twice as old as we previously thought. Science books generally say the Sahara is aboutaroundforfrominofon three million years old. However, a new study aboutaroundforfrominofon a centre aboutaroundforfrominofon climate research aboutaroundforfrominofon Norway says it could be around seven million years old. Researchers used computers to try and calculate when large parts aboutaroundforfrominofon North Africa became desert. Their tests showed that global warming seven million years ago dried a lot aboutaroundforfrominofon the land in what is today the African nation aboutaroundforfrominofon Chad. A sea called the Tethys Sea started shrinking. This made the African summer monsoons less frequent, which helped form sand dunes aboutaroundforfrominofon Chad. The scientists say this is how the Sahara first started.

The Sahara is one aboutaroundforfrominofon the world's best-known and largest deserts. It covers aboutaroundforfrominofon 10 per cent of the whole African continent and forms large parts aboutaroundforfrominofon Algeria, Chad, Egypt, Sudan and other nations. The sands stretch aboutaroundforfrominofon the Atlantic Ocean aboutaroundforfrominofon the west to the Red Sea in the east. Not everyone agrees that the Sahara is as old as the Norway research says it is. Stefan Kröpelin, a geologist aboutaroundforfrominofon Germany, says real geological evidence is needed to be sure. He said the Norway research is based aboutaroundforfrominofon numbers and not evidence, saying: "Nothing you can find aboutaroundforfrominofon the Sahara is older than 500,000 years old". He added that our knowledge aboutaroundforfrominofon the Saharan climate is only aboutaroundforfrominofon 10,000 years ago and that our knowledge is "full aboutaroundforfrominofon gaps".