If you looked down at the Sahara from space right now, instead of a barren desert, you would see a surprising sight—dry land dotted with lakes and rivers in Morocco and Algeria. All thanks to heavy rains in early September 2024. These are not oases, but rather the Sahara slowly “resetting to factory settings.” Believe it or not, millions of years ago, the world’s largest desert was a lush, green land.
So how did the Sahara become a desert? During the last ice age, the Earth was much colder, and large ice sheets covered a significant portion of the land. Back then, the Sahara was much larger than it is today, and there were far fewer rainforests. The cold temperatures changed the pattern of rainfall in the tropics. Normally, warm air rises and produces rain, but as the weather cools, this system is disrupted, leading to less rainfall, turning many areas into drier regions.
However, around 12,500 years ago, something unexpected happened—the amount of dust in the air dropped significantly, suggesting that the Sahara began to become wetter. This suggests that the climate suddenly warmed for a while before cooling again. The Sahara then became a green, steppe-like land, thanks to the shift of the Intertropical Convergence Zone (ITCZ) northward in the summer. This peaked around 4,000 years ago, when temperatures were slightly higher than they are today.
However, another major event—known as the Heinrich event—caused the ITCZ to shift back southward, causing the Sahara and the Arabian Peninsula to dry out rapidly. As a result, from around 2700 to 2100 BC, flooding of the Nile River decreased significantly. Overall, the Sahara has gone through many cycles of dryness and wetness over thousands of years due to changing climate and weather patterns.
Most recently, in September 2024, a rare storm hit the Sahara, affecting Morocco, Algeria, Tunisia, and Libya. Before-and-after satellite images from NASA show a dramatic change—the Sahara looked “refreshed.” Some areas in North Africa received up to 20 centimeters of rain, a remarkable amount when compared to Seattle’s average annual rainfall of 100 centimeters. Surprisingly, this rain fell in just a few hours, making the Sahara appear “wetter” than Seattle at that moment.
The rainwater flowed into temporary lakes in northern Algeria, expanding to over 180 square kilometers and reaching depths of more than 2 meters—enough to hold water for a year. But how do these lakes survive in such a dry desert? Normally, dry soil acts like a sponge, absorbing water, but the Sahara’s soil is so dry that it can only absorb a limited amount of water. So water collects in low-lying areas, forming temporary lakes.
The presence of these lakes does not mean that they do not have names. For example, one of the most beautiful lakes, surrounded by swaying palm trees, is called Yasmina Lake, located in the oasis town of Merzouga. In areas with high sand dunes, you might think you are seeing a mirage, but the sand is actually covered with water. Some areas have been flooded so severely that palm trees are submerged to the tops.
The last time the Sahara saw such heavy rain was 30 to 50 years ago. Morocco especially needed this rain after six consecutive years of drought. Lakes that had been dry for decades, like Iriki Lake, are finally being replenished. Statistics show that since 2000, the region has experienced hundreds of storms, but only six have brought enough rain to fill the lakes, and only two of those have brought lake levels higher than they were in September 2024.
So will the Sahara continue to green? The answer is yes. As moist air from the equator meets hot, dry air from the north, the Sahara can receive more rain. Scientists say this interface is shifting northward due to global warming and is likely to continue moving in the coming decades.
However, not all the news is positive. No one was really prepared for such flooding in the already dry land. Heavy rains have already caused severe damage, killing at least 18 people in southern Morocco. Local authorities are now preparing for more heavy rains in the future.
But what if the Sahara gradually disappears? It may sound strange, but our planet actually needs deserts. The Sahara is not just a dry land, but also plays an important role in the ecosystem. It is a huge carbon storehouse, with an estimated 1,000 billion tons of carbon locked away. In the fight against climate change, deserts like the Sahara act as a “buffer”, helping to keep temperatures within acceptable limits.
Sand from the Sahara is also a vital source of nutrients for tropical forests. Sand particles from the desert travel across the Atlantic Ocean, wind their way to South America, and are deposited in the soil of the Amazon basin. Without the Sahara, experts fear the Amazon could collapse dramatically.
