There's a few threads on here that deal with climate in a rather detailed way ... here's the short short version for this step: There's a band of jungle around the equator, surrounded by 2 bands of desert, one centered on each of the tropic lines (23 degrees north and south). I'm working on a similar world map, so I made a modified gradient that takes the latitude climate zones into effect (you'll still need to modify for mountains/currents if you want true realism). The gradient's attached. The colors are slightly modified from the atlas tutorial: light green is a temperate zone, and the dark green is jungle.