It looks like there are research works trying to define precisely this notion of existential risk in the context of climate change, see e.g. https://link.spring

It looks like there are research works trying to define precisely this notion of existential risk in the context of climate change, see e.g. https://link.springer.com/article/10.1007/s10584-022-03430-y https://link.springer.com/article/10.1007/s10584-022-03430-y