content: I think you're misunderstand what they are saying. We're leaving behind markers in the ground that will be uniquely identifiable. Climate change (or as you called it -- global warming) is a real thing but this isn't really saying that. It's merely noting that our actions may have a visual effect that in the distant future we humans will be able to look back and go "hmm, look at that!" in much the same way we look at other geological ages. This is more of a "here's what we've done" instead of a "here is where we are going". At least this is how I read it.