This factors in some feedback loops which most sudies to date have ignored. Note, that it excludes extra warming caused by all the additional water vapour in the air.
For context, studies suggest that the largest extinction event in Earth’s history (so far), the Late Permian Extinction Event, saw temperature rises of around 8°C.
I linked to that back in 2016 and no one took it seriously. It was a what if scenario back then. Now I’m like they knew