earth definitely used to be a lot warmer, what's different is that there weren't billions of humans that starved if it didn't rain or the water level increased 2 meters.
i seriously hope you aren't retarded enough to believe that fusion happens in earth mantle or that the 0.000...1 ppb radioactive isotopes heat the earth.
btw CO2 levels (rock weathering) are literally used when determining glaciation, climate, etc, if you deny emission spectrums you are pretty much denying all geology and physics. and the spike in the Ordovician is an anomaly that happens to coincide with a mass extinction event. that graph is also a bit fucky, picrel is a more accurate one and you can read more about this here
https://www.sciencedirect.com/science/article/abs/pii/S003101821000115X?via%3Dihub (use scihub)
