Circa 1995, I ran into a couple of British fellows who have put together a project of re-foresting most of the Sahara. They would use desalinatization plants and pipelines to irrigate parts of the Sahara to get patches of trees growing. This would change the climate condusive to more rainfall in the region. Or perhaps better said, 1 liter of desalinated sea water would be recyled several times in the region.
They had a pretty extensive website with this project. Definitely more visionaries than wishful thinkers.
Unfortunately, I can't seem to find that website. It used to known as "The Sahara Project."