Biomes on the surface won't affect caves

That's really weird that deep caves under the surface still have biome data from above the surface. You try to spawn the snow golem at the level -50 and suddenly it dies, because apparently there is a desert somewhere above. 3D biomes is a really hard idea to implement but we can just add the limit for the surface biome to be active under the world. For example, 10 blocks under the surface - and you are in a 'Common Cave' biome instead of 'Desert'. Or this limit can be hard set to the water level or to the level ~60 instead of the surfasce level, this shouldn't be hard to implement.