Is Climate Change a Threat to Human Existence?

If we follow current policies, we'll probably end up seeing around 2 to 3 degrees Celsius of warming by 2100. Cariva and Caranza at the Cambridge Center for the Study of Existential Risk concluded that ecosystem collapse is extremely unlikely to pose risks to human existence. But does this conclusion adequately take uncertainty into account? After all, any time we try to use what we've discovered so far to make predictions about the future, we have to be aware that there could be things we don't know," they say.