There's also a positive feedback loop between ice cover and increasing atmospheric CO2, since an Earth covered in ice prevents a lot of the natural absorption o

There's also a positive feedback loop between ice cover and increasing atmospheric CO2, since an Earth covered in ice prevents a lot of the natural absorption of CO2, allowing the atmospheric CO2 to rise via volcanic outgassing. There's also a theory that a sudden decrease in solar radiation can trigger iceball earths -- https://news.mit.edu/2020/sunlight-triggered-snowball-earths-ice-ages-0729 https://news.mit.edu/2020/sunlight-triggered-snowball-earths...