How does Earth’s precession affect rainfall in the Sahara Desert?

The Sahara Desert’s climate oscillates between arid and humid phases due to Earth’s precession, a 26,000-year cycle involving a wobble on the planet's axis.21

Currently, Earth reaches perihelion—its closest point to the Sun—during the Northern Hemisphere's winter, resulting in more indirect sunlight for the Sahara and limited rainfall. During "African Humid Periods," however, precession aligns perihelion with the Northern Hemisphere's summer. This alignment increases solar radiation by approximately 7 percent, significantly heating North Africa.21

This intense heating creates a large area of rising warm air that draws in humid tropical air from the Atlantic. This process effectively "supercharges" the West African monsoon, allowing it to penetrate deep into the desert and transform the arid landscape into a lush, verdant region filled with rivers, grasslands, and woodlands.1