All solid points. However, I just want to add here that Harper’s “The Fate of Rome”, which tried to compile as much of the climate data as possible, argues that the steppe as a whole along what is today Kazakhstan was drying in this period. It probably forced the Huns to move rather than forced them to become raiders in the first place. We see something similar going on along the North Sea coast, with settlements slowly becoming flooded due to rising tides, possibly playing a role in migration to the British isles