urgh it is going to take awhile for me to learn this 
I think maybe we should add a bit of realistic climate factors? Like how deserts would form along 30 degrees north and 30 degrees south or jungles located within 20 N and 20 S?
Don't make this complicated.
TG2 can use what's called an "image map". Or simply put: You paint in some drawing problem the rough areas where you want a desert to be, and tell it to use desert shaders/colours in that area.
Yes, you could also set up some kind of complicated node network to procedurally define the area based on characteristics, but that's way too complicated. And drawing them gives you more control over placement.
Enough talk. Where are my volunteers? Who wants to help out, and where?
