It is believed that the increase in dust associated with cold periods has three causes:
- Increase desertification,
- Increased in land area (due to falling sea levels)
- Increased winds.
Of these the predominant one is increased desertification. The increased land area due to falling sea levels is small relative to the area of the earth and lower temperatures would suggest that less energy would be available for winds.
Analysis of the dust shows that most of the dust deposits are from the hemisphere where the ice core was taken. On the other hand the synchronicity of the northern and southern ice-cap records suggests that the increase in desertification in ice ages was a global phenomenon. The corollary is that warm periods are associated with less desertification.