For last 33.9 million years, we have been living in an Icehouse global climate. The only thing colder than icehouse is a Snowball Earth climate- and there no real evidence that Earth has ever had one. But during a glacial period, Earth is closer to a snowball or slushball Earth.
As far as we know, 20,000 years ago was pretty much as cold as Earth can get. It was so cold that Global CO2 levels was close to extinction levels of low global CO2 levels.
For last 33.9 million years, we have been living in an Icehouse global climate. The only thing colder than icehouse is a Snowball Earth climate- and there no real evidence that Earth has ever had one. But during a glacial period, Earth is closer to a snowball or slushball Earth.
As far as we know, 20,000 years ago was pretty much as cold as Earth can get. It was so cold that Global CO2 levels was close to extinction levels of low global CO2 levels.