This and other interesting global relationships are covered in an episode on Nova (http://www.pbs.org/wgbh/nova/earth/eart ... space.html) underscoring the fact that causing shifts in global weather patterns may come with unforeseen repercussions.
This dust, much of it originating in an ancient lake bed in Chad...
I recently saw a fantastic BBC program about the making of the African continent (and its origin in the huge Gondwanaland and the even huger Pangea). In this program it was said that (much of) present-day Sahara was once a huge, shallow sea, full of nutrients. That sea is very long gone, but many nutrients remain in the dust.