If you look at things from the geological time scale humanity has existed in an ice age, in what has been seen as an interglacial period.
That's not a coincidence, is it.
Earth's climate, for much of its history, was not well suited to human life. Even during the cretaceous period, an extremely short time ago in geological terms, summer temperatures in what is now the temperate northern hemisphere would have routinely reached levels humans cannot survive. However, the climate wasn't just warmer in general, it was more volatile and unpredictable (which is what "lively" means, I guess). Seasonal variation could be more extreme, weather was less predictable and more destructive. A relatively small number of humans could survive in the few habitable regions of that world, but our current human civilization could not.
That is the risk we take now. Beyond the mass-extinction and significant reduction in global biodiversity that is now basically inevitable, if the speed or severity of climate change goes beyond the limits of what our current civilization is capable of adapting to, the results will be extremely "subjectively bad" for many people, and many of those people will go on to become objectively dead.
I mean, at this point it's already happening. We can't stop it, but we can save millions (if not billions) of human lives by limiting the severity.
