Climate change is bad because it could catastrophically reduce the number of human lives by killing a bunch of people through famine and disease.

That’s not at all the same thing as reducing birth rates - which is voluntary and does not cause death and suffering.

This is paperclip-optimizer logic. Climate change is a problem of irreversible ecological destruction and mass human suffering; pumping out more people as though it's a metric to be inflated is Missing The Point.

> Climate change is bad, because it could reduce the number of human lives.

No, climate change us bad because it can increase SUFFERING. To say that reduction of human lives is bad is to say we should be reproducing as much as possible. Have you maximized the number of people you have had sex with today?

Yes, I think people choosing not to have children is substantially better than death by climate disaster.

Clever, but incorrect. This is a rhetorical construction which falls apart if you don't overload the word, "reduce."

Climate change is bad because it can end human lives. The lives which it doesn't end may experience significant hardship and unhappiness.

Decreasing the rate of population growth does reduce the number of existing humans, but it doesn't induce that reduction by ending lives. It also doesn't increase the amount of hardship imposed on most humans.

Do you see why climate change and population reduction are not comparable?

Reducing the number of humans reduces a large amount of resource contention.

By not giving birth to more humans we're not killing people off. Alternative, as we see in many places, is war. War is definitely not the same thing as avoiding pregnancies.

How disingenuous. Choosing not to have children is not the same as death by climate catastrophe or death by any other means.

Climate change is bad for a lot of reasons (e.g. individual quality of life), in addition to that one.