Stephen Hawking has said we are destroying earth and need to leave. This is a real recognition of the Anthropocene. However:
1) It will cost a huge amount to find an inhabitable planet and get there and set up a colony. This is money which could be spent fixing the problems we have here – such as winding back coal burning and other forms of pollution, developing an asteroid defense programme, or getting rid of nuclear weapons.
2) We will probably never be able to transport a couple of billion people off this planet – so the process of leaving involves deciding who will survive, and enforcing that decision. Which elite will survive? Probably the elite that have stuffed the planet in the first place. Who will be left to die? Probably you.
3) As the saying has it: “Wherever you go, there you are”. If we don’t fix up our social systems, the tendency to favour the powerful who are benefitting from the emissions which cause climate change, alter our tendency to say it is everyone else’s fault, or that there is no problem in what is comfortable to us, then some humans will simply all die off in some distant place.
4) If we plan to leave, then our destruction of the earth will accelerate, because if it is going to get destroyed anyway, what is the point in leaving it intact? This will increase the emergency, and probably decrease the chance of making it into space successfully. It will probably mean even more people die earlier than they would have.