Using the worldbuilder save attached I used three nukes and started getting fallout where I didn't drop nukes, and after nine I got freezing. When testing put the GLOBAL_WARMING_PROB and NUCLEAR_WINTER_PROB to 100. The 99 forge is what I've been using just to make sure it can happen i.e. the code works. I haven't yet produced a good map that is just like a late game map played from the beginning so I can adjust the tree GLOBAL_WARMING_*_WEIGHT values to see what produces GW under those circumstances. Setting GLOBAL_WARMING_UNHEALTH_WEIGHT to 20 would be the same as it was originally, but since recycling can counter that now it might be fine. That would just leave power and bonus unhealth, which might not be enough to trigger GW on their own but would make it worse with building unhealth.