“How can we be so arrogant? The planet is, was, and always will be stronger than us. We can't destroy it; if we overstep the mark, the planet will simply erase us from its surface and carry on existing. Why don't they start talking about not letting the planet destroy us?”
― Paulo Coelho, The Winner Stands Alone
That's really it. When we have pushed the atmosphere and the oceans out of the narrow band of chemical and temperature tolerances known to them for millions of years, the earth will be unfit for most of the current plants and animals. The 3rd great extinction. The anthropocene will peter out in an empty concrete lined urban riverbed.
Picture above: dust storm, Arizona, 2012, once rare, the last couple of years have seen a number of them. Can you say harbinger?