This just completely and naively sidesteps the issue though? "Save the earth" or whatever is obviously a simplification and a euphemism, a marketing approach no

This just completely and naively sidesteps the issue though? "Save the earth" or whatever is obviously a simplification and a euphemism, a marketing approach not a moral necessity. What we're obligated to prevent is avoidable human death and suffering on a massive scale. It is the lives that matter not the origin of the threat. And it's not a simple dichotomy between total extinction and we're all fine. A plausible scenario is that hundreds of millions of people who are living right now will die preventably, and those with the most resources, including fossil fuel use, will be able to ride it out at their expense. We have obligations going beyond merely weakening the mechanisms of climate change; we must also address its consequences now and in the near future.