This is extremely irresponsible (and I cannot believe how many utterly ill-informed comments you've gotten).

The variation in mean temperature over the surface of the earth is enormous--the warmest places (difficult to live in, but people do live there) have a mean temperature of around 30C. The mean temperature of the very warmest part of Antarctica is about -2C.

Even without any technological help whatsoever, humans can easily survive the very largest expected changes, plus a couple of "OMG what if" additions. We're highly mobile. We can travel--some of us can travel, even if billions die--to habitable regions.

Now, it is true that instability from climate change, or geopolitical maneuvering, or economic downturns, or wars, or whatever else could induce us to obliterate human life via an all-out exchange of nuclear weapons. Even that I think is pretty unlikely to work--who is going to bomb the Andaman Islanders, for instance?--but it is not so far outside the realm of possibility that we could be completely confident.

But in this way, climate change is no different than numerous threats: they all become existential because we can now threaten our own existence, and for no other reason.

On its own, without us self-destructing, climate change it may be calamitous indeed, but not that calamitous.

Being unable to make these vast distinctions is a key part of why dangers of all sorts can become existential: because we encourage people to be too stupid to understand the difference in gravity.

You are part of the problem. Please stop.