If the entire world went to zero carbon emissions tomorrow, the effects would still be serious. Given that's not going to happen, the effects are likely to be catastrophic.

You're right that it won't mean the extinction of life on earth or humanity, but it might turn out to be the end of advanced human civilization if the bad end of the predictions come to pass. If there's not enough arable land left to support the human population, things will get very ugly very quickly.

I doubt it will mean the extinction of humanity, but unless a couple of miracles happen it will mean the end of our current industrial civilization.

If we had started working on this 40 years ago reaching zero emissions would be a realistic goal today, but even that is not enough now. Not only we need to reach zero emissions ASAP, but we also need strong negative emissions. And after that we need to figure out how to slow down the feedbacks (Arctic ice melting, methane, etc).

Maybe if ALL humanity was working towards those goals we would have a chance, but it's not even a priority for the vast majority of humans.