I was watching a documentary on the Sahara region of Africa the other day, and there was one sentence that caught my attention--that due to changes in the Earth's orbit, the rains were driven to the south, creating the Sahara Desert within a matter of decades.
I was curious, so I looked up the phenomena on Wikipedia. It's called the Orbital Monsoon Hypothesis and was first suggested by Rudolph Spitaler in the 19th century. Developed and tested by meteorologist John Kutzbach in 1981, it has to do with how much sunlight falls on the continents during the summer months, which in turn creates the monsoons.
The wobble of the Earth on its axis, the eliptical shape of its orbit, and its axial tilt at perihelion, all play a part in determining how much insolation occurs, which affects the strength and direction of the monsoons.
The article has the proper scientific terms and math, and is really quite intriguing, especially in this era of "human-cenrtric climate change" paranoia that's driving politics.