[lopmotr]

100's of millions is not necessarily an existential crisis because it already happened in the 1900's due to war, disease, and famine. Even if that absolute scale of deaths happens again because of climate change, it will be proportionally smaller due to the global population being an order of magnitude larger.

Do you have a reference to that prediction of it probably killing 100's of millions of people? On it's own, it doesn't really mean much because what time scale and what's the no-climate-change number to compare to?

[akie]

Famine, meteorites, large scale war, atomic bombs, infectious disease, the plague - all survivable by society at large. With your definition almost nothing qualifies as existential crisis.