One thing to keep in mind, Joe. The earth has been busy sequestering atmospheric carbon since at least the Permian era. That sequestering takes the form of coal, petroleum, natural gas and methane hydrate (in the deep oceans). Humanity has been busy releasing all of that carbon (by burning fossil fuels) and has undone the work of hundreds of millions of years in just a couple of centuries. How can that not have a significant effect? It is certainly true that the sun's luminosity fluctuates over time. Precession and changes in earth's magnetic field may cause climate change as do movements of the tectonic plates. But humanity's denial of its own part has more to do with discomfort at what lies ahead. A large and increasing number of scientists (especially those not being financed by the extraction industry) are convinced that we play a noticeable role in these changes.
My son and I have been politely disagreeing about that for a while. I maintain global warming is occurring and that probably we have something to do with it -- but it's been warming since the end of the Pleistocene and our contribution may be minor. He takes the position we're to blame. Thanks, Joe