Why Sahara desert turning green from arid yellow?

Parts of the Sahara Desert—a vast area typically characterized by its arid, yellow landscape—are turning green following unprecedented rainfall. Satellite imagery has revealed this shift, showcasing green vegetation emerging where the desert's sandy dunes dominated. This transformation has stunned scientists and environmentalists, raising questions about climate change's role in altering one of the planet's most inhospitable regions.

Sahara Desert turning green unexpectedly

By late September, parts of the Sahara will have received up to five times the usual rainfall, turning barren areas into temporary wetlands and oases. According to NASA’s Earth Observatory, the Sahara typically gets only a few inches of rain per year, making the deluge extraordinary.

An extratropical cyclone over the Sahara Desert drenched parts of Morocco and Algeria – bringing up to a year’s worth of rain to some areas. 🌧️ @nasa’s Terra satellite captured floodwaters and some Saharan lakes, usually dry, filled with water. https://t.co/cuS1c73RoA pic.twitter.com/m8Ga8G0FgO

— NASA Earth (@NASAEarth) September 17, 2024

Early September satellite images showed an extratropical cyclone—typically not classified as a tropical cyclone—hitting the region on September 7 and 8. This rare event left vast runoff water across the desert. NASA’s MODIS (Moderate Resolution Imaging Spectroradiometer), aboard two satellites capturing Earth’s surface daily, confirmed the change. Comparing images, scientists observed an increase in water accumulation, with varying blue shades representing different depths. Notably, green patches of vegetation appeared, indicating a rare desert greening process.

A striking change occurred in the normally dry Sahara lakes. After heavy storms, some filled with water, creating lush green surroundings. This transformation reminds us of the desert’s capacity for change, despite its reputation for desolation.

Scientists attribute the unprecedented rainfall to the shifting of the Intertropical Convergence Zone (ITCZ), a stormy weather belt near the equator where the Northern and Southern hemispheres’ trade winds meet. Typically, this zone hovers near the equator, but this year, it has shifted unusually far north, bringing thunderstorms and heavy rainfall to the northern Sahara Desert.

These images, captured by #VIIRS onboard the #NOAA21 satellite on Aug. 30 and Sept. 9, 2024, use enhanced color to highlight rain accumulation in the Sahara Desert.

Clouds are shown in light cyan, while water is dark blue to indicate moisture content.

Credit: @NOAA/@CIRA_CSU pic.twitter.com/SkFsuUPfJb

— Joint Polar Satellite System (JPSS) (@JPSSProgram) September 13, 2024

Climate patterns caused Sahara rainfall

Global climatic patterns influence the ITCZ's movement. According to Karsten Haustein, a climate researcher at the University of Leipzig, two factors contributed to this year's unusual shift: the transition from El Niño to La Niña and global warming. El Niño, with warmer Pacific ocean temperatures, leads to drier conditions in Africa. La Niña, which brings wetter weather, amplified this year's northern Sahara rainfall.

The warming of the world’s oceans, especially the North Atlantic and Mediterranean, may have played a role. Warmer sea temperatures increase evaporation and moisture in the atmosphere, resulting in heavier rainfall during storms. As a result, the Sahara has received more rain than expected, raising concerns about more frequent weather patterns.

See how #ATMS data from the #NOAA20 and NOAA/NASA #SuomiNPP satellite, combined with data from other satellites, track rainfall in the Sahara.

This blended rain rate product reveals the amount of rain falling at around 1 to 6 millimeters per hour from Aug. 30 to Sept. 9, 2024. pic.twitter.com/1NNoEedkBj

— Joint Polar Satellite System (JPSS) (@JPSSProgram) September 13, 2024

The greening of the Sahara Desert may signal future climate change impacts. Haustein explains that as the world warms, the ITCZ is expected to shift further north in the coming decades, bringing more rain to the Sahara and other arid regions.

A recent Nature study suggests that as global temperatures rise, the ITCZ could move northward more frequently, leading to increased rainfall in areas like the Sahara.

While the Sahara’s transformation seems positive, increased rainfall has devastated nearby countries. Torrential rains have triggered catastrophic floods across North Africa, displacing millions and killing hundreds. This year’s floods have affected 1.5 million people in Chad alone, with at least 340 fatalities. Similarly, heavy rains in Nigeria, Sudan, and Libya have caused destruction, as dry areas can’t handle sudden flooding.

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