Since the 1980s, the Sahara has shrunk by roughly 8%. Satellite data show widespread greening, a pattern that is playing out across the planet. Around 50% of Earth's vegetated land has become significantly greener, an area roughly three times the size of the United States. The dominant driver is not rainfall or land use change, it is rising atmospheric CO2. Higher CO2 lets plants photosynthesize more efficiently, they lose less water, they tolerate heat and dryness better. The effect is strongest along desert margins - across the Sahel, the Middle East, Australia's interior and the southern edge of the Sahara. Rising CO2 is making the deserts, and the planet as a whole, greener.