Not a Single Scorpion
While satellite images can't distinguish temporary plants like grasses that come and go with the rains, ground surveys suggest recent vegetation change is firmly rooted.
In the eastern Sahara area of southwestern Egypt and northern Sudan, new trees—such as acacias—are flourishing, according to Stefan Kröpelin, a climate scientist at the University of Cologne's Africa Research Unit in Germany.
"Shrubs are coming up and growing into big shrubs. This is completely different from having a bit more tiny grass," said Kröpelin, who has studied the region for two decades.
In 2008 Kröpelin—not involved in the new satellite research—visited Western Sahara, a disputed territory controlled by Morocco.
"The nomads there told me there was never as much rainfall as in the past few years," Kröpelin said. "They have never seen so much grazing land."
"Before, there was not a single scorpion, not a single blade of grass," he said.
"Now you have people grazing their camels in areas which may not have been used for hundreds or even thousands of years. You see birds, ostriches, gazelles coming back, even sorts of amphibians coming back," he said.
"The trend has continued for more than 20 years. It is indisputable."
An explosion in plant growth has been predicted by some climate models.
For instance, in 2005 a team led by Reindert Haarsma of the Royal Netherlands Meteorological Institute in De Bilt, the Netherlands, forecast significantly more future rainfall in the Sahel.
The study in Geophysical Research Letters predicted that rainfall in the July to September wet season would rise by up to two millimeters a day by 2080.
Satellite data shows "that indeed during the last decade, the Sahel is becoming more green," Haarsma said.
Even so, climate scientists don't agree on how future climate change will affect the Sahel: Some studies simulate a decrease in rainfall.
"This issue is still rather uncertain," Haarsma said.
Max Planck's Claussen said North Africa is the area of greatest disagreement among climate change modelers.
Forecasting how global warming will affect the region is complicated by its vast size and the unpredictable influence of high-altitude winds that disperse monsoon rains, Claussen added.
"Half the models follow a wetter trend, and half a drier trend."
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