Even without tipping points, 3C is incredibly hazardous to human life. Large swathes of the planet, especially near the equator, go from "barely habitable" to "uninhabitable". Many millions will die; hundreds of millions (possibly billions) will be displaced.

Even in the temperate zones, agricultural zones will shift tens or hundreds of miles toward the poles, where the growing seasons will be shorter due to daylight. Centuries of infrastructure will have to be rebuilt from scratch, if it can be done at all.

The tipping points have the potential to be globe-spanning catastrophes. But even if we get lucky and none of them happen, there are disastrous effects that we are absolutely certain about.