Gary Gilligan has a post up at Thunderbolts – see www.thunderbolts.info/wp/daily-tpod/ (Oct 28th) on the subject of the Sahara desert, the amount of dust that is blown across the Atlantic, and how it seeds rain that falls on the rainforest. He asks, what happened when the Sahara was largely a savannah? Did it effect rainfall in Brazil? As always, the issues are not simple. Was the axis of rotation the same as it is today and if it wasn't, how did this affect desertification? Lots of questions.