It isn't. Arrakis suffered desertification before humans ever arrived, before the book even began. The only climate change that occurred thereafter was a direct result of Pardot Kynes convincing the Fremen they could terraform Arrakis and, after Paul Atreides defeated the Emperor Shaddam IV Corrino and seized control of the Imperium, and subsequently began a deliberate effort to accelerate the terraforming effort until, by the time of God Emperor of Dune, the desert has been pushed back to just a tiny portion of the planet.
TL;DR The entire article is someone with an axe to grind trying to use Dune to do it. Scroll on.