<p> The Sahara - largest hot desert in the world - was a green and lush area covered in vegetation 5,000 to 11,000 years ago, with rainfall up to ten times more than it is today, according to a new study.<br /><br /></p>.<p>The Sahara Desert was home to hunter-gatherers who made their living off the animals and plants in the region's savannahs and wooded grasslands, researchers said.<br /><br />The study pinpointed the rainfall patterns in the Sahara during the 6,000-year "Green Sahara" period by analysing marine sediments.<br /><br />"It was 10 times as wet as today," said lead author Jessica Tierney of the University of Arizona (UA).<br /><br />Annual rainfall in the Sahara now ranges from about four inches to less than one inch.<br />Although other research had already identified the existence of the Green Sahara period, Tierney and her colleagues are the first to compile a continuous record of the region's rainfall going 25,000 years into the past.<br /><br />Archaeological evidence shows humans occupied much of the Sahara during the wet period, but left for about a thousand years around 8,000 years ago - the middle of the Green Sahara period.<br /><br />Other researchers have suggested the Sahara became drier at the time people left, but the evidence was not conclusive, said Tierney, a UA associate professor of geosciences.<br />Her team's continuous rainfall record shows a thousand-year period about 8,000 years ago when the Sahara became drier. That drier period coincides with when people left, she said.<br /><br />"It looks like this thousand-year dry period caused people to leave," Tierney said.<br />"What's interesting is the people who came back after the dry period were different - most raised cattle. That dry period separates two different cultures. Our record provides a climate context for this change in occupation and lifestyle in the western Sahara," he said.<br /><br />Researchers used their rainfall record to suggest ways current climate models can better replicate the Sahara's ancient climate and therefore improve climate projections.<br /><br />They had long known the Sahara was much greener in the past, but how much of the Sahara was wetter and how much wetter was not well understood, Tierney said.<br /><br />Although scientists can learn about past climate by examining ancient lake sediments, in the Sahara the lakes dried up long ago and their sediments have blown away.<br /><br />Instead of lake sediments, researchers used cores of marine sediments taken off the coast of West Africa at four different sites.<br /><br />As the cores were taken over a north-south distance of about 1,300 km - from offshore Cape Ghir, Morocco, to the northwest of Mauritania - the cores revealed both the ancient rainfall patterns and the areal extent of the Green Sahara.<br />The research was published in the journal Science Advances. <br /></p>
<p> The Sahara - largest hot desert in the world - was a green and lush area covered in vegetation 5,000 to 11,000 years ago, with rainfall up to ten times more than it is today, according to a new study.<br /><br /></p>.<p>The Sahara Desert was home to hunter-gatherers who made their living off the animals and plants in the region's savannahs and wooded grasslands, researchers said.<br /><br />The study pinpointed the rainfall patterns in the Sahara during the 6,000-year "Green Sahara" period by analysing marine sediments.<br /><br />"It was 10 times as wet as today," said lead author Jessica Tierney of the University of Arizona (UA).<br /><br />Annual rainfall in the Sahara now ranges from about four inches to less than one inch.<br />Although other research had already identified the existence of the Green Sahara period, Tierney and her colleagues are the first to compile a continuous record of the region's rainfall going 25,000 years into the past.<br /><br />Archaeological evidence shows humans occupied much of the Sahara during the wet period, but left for about a thousand years around 8,000 years ago - the middle of the Green Sahara period.<br /><br />Other researchers have suggested the Sahara became drier at the time people left, but the evidence was not conclusive, said Tierney, a UA associate professor of geosciences.<br />Her team's continuous rainfall record shows a thousand-year period about 8,000 years ago when the Sahara became drier. That drier period coincides with when people left, she said.<br /><br />"It looks like this thousand-year dry period caused people to leave," Tierney said.<br />"What's interesting is the people who came back after the dry period were different - most raised cattle. That dry period separates two different cultures. Our record provides a climate context for this change in occupation and lifestyle in the western Sahara," he said.<br /><br />Researchers used their rainfall record to suggest ways current climate models can better replicate the Sahara's ancient climate and therefore improve climate projections.<br /><br />They had long known the Sahara was much greener in the past, but how much of the Sahara was wetter and how much wetter was not well understood, Tierney said.<br /><br />Although scientists can learn about past climate by examining ancient lake sediments, in the Sahara the lakes dried up long ago and their sediments have blown away.<br /><br />Instead of lake sediments, researchers used cores of marine sediments taken off the coast of West Africa at four different sites.<br /><br />As the cores were taken over a north-south distance of about 1,300 km - from offshore Cape Ghir, Morocco, to the northwest of Mauritania - the cores revealed both the ancient rainfall patterns and the areal extent of the Green Sahara.<br />The research was published in the journal Science Advances. <br /></p>