A couple of weeks ago, we talked about some new research into the so-called “Green Sahara” period, and how rainy it was between 8,000-11,000 years ago.

Jessica Tierney, an associate professor of geoscience at the University of Arizona and lead author of a new paper on the Green Sahara, told us about what she found.

"So we found that today, it rains about 2 inches a year in the Sahara, so for reference, that’s much less rain than even the Mohave Desert gets – the Mohave Desert gets about 5 inches. So, about half that," Tierney said. "And then, during the Green Sahara time, as we call it, it was actually raining up to 2 feet a year. That’s comparable to rainfall in San Francisco, so that is a really, really large change."

Well, it turns out another researcher has been looking at some of the reasons why monsoon activity lessened, helping turn the Sahara into the sand dune-covered landscape we know today.

David Wright is an associate professor at Seoul University, in the department of archeology and art history. His paper was published in the journal "Frontiers in Earth Science."