Why don’t you post more than that? Earth exists much longer than this. There are data about Earth temperature for hundreds of milions of years, but it probably doesn’t fit your theory, eg: https://www.climate.gov/sites/default/files/styles/full_width_620_original_image/public/graph-from-scott-wing-620px.png?itok=Jgi659bn
Has there ever been a period in Earth’s history where CO2 concentration in the atmosphere changed this quickly without being accompanied by mass extinctions?
The Paleocene-Eocene thermal maximum is actually a great analogue for what we’re currently experiencing. Huge increase in global temperature over a relatively short period of time, probably due to runaway methane release. It went back to normal within a few hundred thousand years because of increased planktonic CO2 sequestration in the expanded tropical zone.
I think the point isn’t so much that Earth will heat up but that it will do so at a tremendous pace (in geological timescales). Nature can’t adapt so quickly. Basically it will lead to a mass extinction simply because of how quickly it is happening. Nature takes a longer time to genetically adapt to a changing environment than humans have even existed. That’s the problem.