You can't change the settings for the map, because you wouldn't want to change them (you wouldn't want grassland in the middle of the Sahara desert for example). The map is pre-set for map size. It's a custom map. Selecting climate, age, etc, would generate a whole new map and would look nothing like the world anymore.
If you want to add variety to a world map, you can open up the scenario in the editor and re-distribute natural resources (and/or starting locations, goody huts, etc) so that all the resources won't show up in the same places all the time... (make sure you save it as something else, like 'earth(huge2)', though in case you want to go back to the original).