According to the records, it had a fairly normal weather pattern when it was first settled. Then, as the population grew and urbanization spread, more energy was used and more heat was discharged into the atmosphere. The ice cover contracted, the cloud layer thickened, and the weather got lousier. That encouraged the movement underground and set off a vicious cycle. The worse the weather got, the more eagerly the land was dug into and the domes built and the weather got still worse.