I figure the lore they have is pretty much placeholder lore, to be refined when they focus on individual provinces down the line. True, Cyrodiil's had a massive overhaul, but you can't deny it makes the world more believable and immersive as a result. The other thing to consider is that Skyrim isn't all snow and ice, and so although there will undoubtedly be some http://www.therealfun.com/wallpapers/Fantasy_Desktop_10818.jpg, there will be other climates and horizons to view.
It's also fairly evident that TES lore is written to be debated, just like real life lore. Far too many people assume that just because it is written, it must be true, because TES is just a game series and couldn't possibly have that much depth. Who's to say that Cyrodiil wasn't always grassland and forest, and that those jungles have become a popularized religious story? That's why 'lore changes' in this series can work, and why I love these games so much. I don't believe Noah actually gathered two of every animal in the world and crammed them on an ark, so why I should believe that "The planets are the gods and the planes of the gods, which is the same thing. That they appear as spherical heavenly bodies is a visual phenomena caused by mortal mental stress." and other pieces of lore, when all scientific evidence says otherwise. People's beliefs, and lore in general, just realistically reflects the technological limits of the time.