Skip to Content
77 Mass Ave

A Green Sahara

Study finds ancient North Africa was much more lush than previously thought
June 18, 2013

Today the Sahara is a vast desert spanning more than 3.5 million square miles in northern Africa. But as recently as 6,000 years ago it was a verdant landscape, with sprawling vegetation and numerous lakes. Ancient cave paintings in the region depict hippos in watering holes, and roving herds of elephants and giraffes—a vibrant contrast with today’s barren, inhospitable terrain.

NASA satellite image of Sahara Desert dust
This NASA satellite image shows dust from a June 2012 Sahara dust storm extending well past the Canary Islands and Madeira.

The Sahara’s “green” era, known as the African Humid Period, probably lasted from 11,000 to 5,000 years ago and is thought to have ended abruptly, within one to two centuries. Now researchers at MIT, Columbia University, and elsewhere have found that this swift climate change occurred nearly simultaneously across the rest of North Africa.

The team traced the region’s wet and dry periods over the past 30,000 years by analyzing sediment samples collected off the coast of Africa. Such sediments are composed, in part, of dust blown from the continent over thousands of years. The more dust that accumulated in a given period, the drier the continent may have been.

From their measurements, the researchers found that the Sahara emits five times more dust today than it did during the African Humid Period. Their results, which suggest a far greater change in Africa’s climate than previously estimated, are published in Earth and Planetary Science Letters.

David McGee, an assistant professor in the Department of Earth, Atmospheric, and Planetary Sciences, says the quantitative results of the study will help other scientists determine the influence of dust emissions on both past and present climate change.

“Our results point to surprisingly large changes in how much dust is coming out of Africa,” says McGee, who did much of the work as a postdoc at Columbia. “This gives us a baseline for looking further back in time, to interpret how big past climate swings were.”

As a next step, McGee is working with collaborators to test whether these new measurements may help resolve a long-standing problem: the inability of climate models to reproduce the wet conditions in North Africa 6,000 years ago. With results that can be used to estimate the impact of dust emissions on regional climate, models may finally be able to replicate the North Africa of that era—a region of grasslands that were host to a variety of roaming wildlife.

“This is a period that captures people’s imaginations,” McGee says. “It’s important to understand whether and how much dust has had an impact on past climate.”

Keep Reading

Most Popular

A Roomba recorded a woman on the toilet. How did screenshots end up on Facebook?

Robot vacuum companies say your images are safe, but a sprawling global supply chain for data from our devices creates risk.

A startup says it’s begun releasing particles into the atmosphere, in an effort to tweak the climate

Make Sunsets is already attempting to earn revenue for geoengineering, a move likely to provoke widespread criticism.

10 Breakthrough Technologies 2023

Every year, we pick the 10 technologies that matter the most right now. We look for advances that will have a big impact on our lives and break down why they matter.

These exclusive satellite images show that Saudi Arabia’s sci-fi megacity is well underway

Weirdly, any recent work on The Line doesn’t show up on Google Maps. But we got the images anyway.

Stay connected

Illustration by Rose Wong

Get the latest updates from
MIT Technology Review

Discover special offers, top stories, upcoming events, and more.

Thank you for submitting your email!

Explore more newsletters

It looks like something went wrong.

We’re having trouble saving your preferences. Try refreshing this page and updating them one more time. If you continue to get this message, reach out to us at customer-service@technologyreview.com with a list of newsletters you’d like to receive.