Sahara Turns Green on a 20,000-Year Cycle, Growing Lakes Up to 350,000 Square Kilometers
Updated
Updated · spacedaily.com · Jul 18
Sahara Turns Green on a 20,000-Year Cycle, Growing Lakes Up to 350,000 Square Kilometers
1 articles · Updated · spacedaily.com · Jul 18
Summary
A 2023 climate-model study reproduced 20 North African humid periods over the past 800,000 years, showing the Sahara repeatedly shifted from desert to grasslands, wetlands and lakes.
About 19,000 to 23,000-year orbital precession drives the pattern by boosting Northern Hemisphere summer sunlight, strengthening monsoon flow into North Africa; vegetation, dust, oceans and ice sheets then amplify or suppress the response.
The last African Humid Period lasted roughly 14,500 to 5,000 years ago, when features including Lake Mega-Chad—more than 350,000 square kilometers—and river systems spread across parts of the Sahara.
Physical evidence matches the climate record: at Gobero in Niger archaeologists found about 200 burials beside a former lake with hippopotamus remains, while Libya's Takarkori site yielded 17,551 animal remains including crocodile fragments and abundant fish.
Sediment records indicate this wet-dry rhythm extends back more than 11 million years, though researchers say future orbital conditions alone cannot predict when a new Green Sahara would return.
If the Sahara turns green again, could the Amazon rainforest collapse without its vital supply of desert dust?
Is climate change turning Saharan dust into a fertilizer for flesh-eating bacteria along American coastlines?
From Desert to Oasis: The Science and Future of the Sahara’s Green Cycles
Overview
The Sahara Desert, now one of the driest places on Earth, has a remarkable history of transforming into a green, lush landscape during 'Green Sahara' phases. These changes happened over the past 800,000 years, mainly due to natural shifts in Earth’s orbit, which affected monsoon patterns and rainfall. Sometimes, these green periods ended very quickly—within just 200 years—showing how fast climate can change. Understanding these past cycles helps scientists predict how the Sahara might respond to today’s climate change, highlighting the importance of learning from history to prepare for future environmental shifts.