The issue with the faith in the earth's own regulation magic is that it also assumes that the regulation magic is friendly to us, and/or that the goal of the regulation is to maintain a steady state which is good for humanity, or that it is even to maintain a steady state (maybe it's idea of 'regulation' is maintaining a chaotic cycle).
I used to joke that climate change was really the dinosaurs trying to come back; we are pumping FOSSIL fuels into the air with an end result of recreating a climate more similar to the warmer days when the dinosaurs roamed.
by issue, I mean "problems even if we assume that the earth's regulatory/homeostatic mechanisms are properly functioning."
That assumption is also problematic, if one allows for the possibility that our technological powers and population size mean we are pushing on the system faster than its regulatory mechanisms can compensate. Our bodies have highly tuned regulatory mechanisms to control body temp, which work amazingly well as long as ambient temps stay within a certain range. Outside that range, not so well.
Well, it, er, does, but it isn't very good (see ice ages), and operates on timescales that would be inconvenient to us. If humanity died out tomorrow, then CO2 levels would likely get back to normal eventually, but it's not really a _great_ solution, is it? We can hopefully do better.