This assumes we won't find a viable alternative. I really like Interstellar for this reason -- I can see us sending x ships to x planetary systems with the understanding that all but one of those ships will likely perish for a greater good.
I think the other reason we want to be on multiple planets is less about climate change, but cataclysmic shocks (asteroid impact, nuclear war, etc.) -- if we're on multiple planets, we have a greater chance of surviving a cataclysmic shock to one planet.
Your point on climate change is great, though -- you're right that if we can terraform Mars or the Moon, we have the technology to fix whatever climate issues are happening on Earth! Funny that this doesn't come up more.
I think the other reason we want to be on multiple planets is less about climate change, but cataclysmic shocks (asteroid impact, nuclear war, etc.) -- if we're on multiple planets, we have a greater chance of surviving a cataclysmic shock to one planet.
Your point on climate change is great, though -- you're right that if we can terraform Mars or the Moon, we have the technology to fix whatever climate issues are happening on Earth! Funny that this doesn't come up more.