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.
Well we couldn’t even be bothered with that step, so I guess we are well and truly fucked. Sionara earth, it’s been fun!