[jfengel]

As bad as climate change is, it will never make Earth harder to live on than Mars. Even the most egregious runaway scenario feedback loops won't make the planet unlivable.

It might be extremely uncomfortable. Billions of people might die. Civilization could collapse utterly.

But it's still going to have more oxygen, better temperatures, and more resources than Mars.

There can be good reasons to go to Mars, but a "backup planet" just isn't really a good one. If all we care about is the survival of the human race, it's really not in jeopardy. Certainly not from climate change, and not even from a war, asteroid, or pandemic.