[gxon]

Mass depopulation is probably the only option either way. Whether it's under our control or forced upon us.

Even if we manage to colonize another world, there's no way we'll be able to scale transportation and settlement fast enough to move enough people off planet to mitigate climate change here.

[noobermin]

This is only true if by mass depopulation you mean of specifically the US and some European countries judging by per capita GHG production.

[gxon]

Depends on the quality of life and final population level. Maybe our options are a billion people living in abject, third world poverty, or a few 10s of millions living a first world, middle class lifestyle. Depopulation will happen until we get to some sustainable ratio, whatever that happens to be.

How we get there might also be the opposite of what you'd expect. Maybe the poorest 6 billion die first, and the remaining rich manage to survive only by drastically ratcheting down their lifestyle. Or maybe world war 3 happens and almost everyone dies, but the small number of survivors are able to pick up the pieces and build something resembling a modern lifestyle.

[noobermin]

I don't think you understand the situation that exists. Climate change is a problem that exists today and so is caused by current consumption levels. The global poor doesn't today produce the overwhelming amount of GHGs, the first world does through its consumption. So, if you want to depopulate anywhere to solve the current crisis, the only place you can depopulate is here.

That said, not all middle class lifestyles need be so carbon intensive. US in particular has the highest GHG per capita because of sprawl and lifestyle choices. As China and India develop (although that might take a while) we have to help encourage them to not copy the US' example but say certain western european countries which use much less GHG per capita that we in the US do.