With all of the humans emitting CO2 from their bodies right now and population increase that happens every year, dreaming of other planets might be the only alternative.
The amount of CO2 human bodies emits is negligable. Methane from cow farts are a significant source of greenhouse gasses though. There should be fincancial incentives for more environmentally friendly diets. As well as greater taxes for air travel. In england it is cheaper to fly than travel by train.
A couple do things have to happen in tandem: 1. Switching to a predominantly plant based diet. Not necessarily fake meat, but reducing our animal protein coming from CAFOs. 2. Restoring habitat because we are a super apex predator and we need ecosystems below us to be functioning well. Insect loss and disappearing bird and reptile population is a scary warning sig. We can achieve habitat rehab with reforestation and rewilding 50% of land mass. It’s a start. 3. Protect marine health and eco system. After all, life on earth is only because of the oceans. 4. Bring most if not all food production indoors. 5. Find alt. Energy with a mix of clean nuclear, renewables and fossil fuels. 6. Bring population down to carrying capacity. There is no way avoiding the issue of depopulation. It is possible with non transferable 1/2 surviving child per person so we have genetic diversity. Alternatively, we can incentivize responsible rationed procreation if they have 1 or no children ..but this would lead to a class system. Procreation shouldn’t be penalized but there is no need to incentivize what is essentially bad for our planet. 7. For the above point, we must develop anti aging and genetic repair and tech to extract and preserve genetic material.
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.
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.
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.