Consequences

 

• All or almost all above ground human settlements are destroyed or rendered uninhabitable.
• Most of humanity is wiped out, with less than 100,000 surviving across the globe in perhaps small, mostly underground, communities.
• The ice age hasn’t made the world completely barren or uninhabitable, and mass extinction didn’t mean total extinction
• What communities that survive can still build a semi-sustainable living
• Most technologies are rendered useless, or at least their construction and maintenance mostly lost to time

 

 

 

 

References: World Building

https://worldbuilding.stackexchange.com/questions/84774/what-kind-of-ice-age-would-cause-an-apocalypse