> So in the end wouldn't worst case scenario be of around time when they formed?
It's worth noting that the Earth's atmosphere would be incompatible with current life at various past levels of atmospheric carbon.
In the past, Earth's atmosphere was almost entirely nitrogen and carbon dioxide[1], but at some point some plucky cyanobacteria learned how to photosynthesize and convert CO2 into O2, hugely changing the contents of the atmosphere [2] and killing a large amount of life that couldn't tolerate the new order.
So if we were to burn all the fossil fuels, it's quite possible that this would cause a climate catastrophe that would kill a large majority of life on earth. But there's a decent chance that the cyanobacteria and friends would survive and, after hundreds of millions of years, restart the evolutionary process.
Note that climate catastrophes take many forms, and the "greenhouse effect" does not even necessarily have to be involved. Take ocean acidification for instance. Atmospheric carbon raises the pH level of the ocean, which can cause cascading ecological collapse.
>But there's a decent chance that the cyanobacteria and friends would survive and, after hundreds of millions of years, restart the evolutionary process.
I think it's worth noting that on this timescale, we don't have forever:
"In about one billion years, the solar luminosity will be 10% higher than at present. This will cause the atmosphere to become a "moist greenhouse", resulting in a runaway evaporation of the oceans. As a likely consequence, plate tectonics will come to an end, and with them the entire carbon cycle... Four billion years from now, the increase in the Earth's surface temperature will cause a runaway greenhouse effect, heating the surface enough to melt it. By that point, all life on the Earth will be extinct." - from https://en.wikipedia.org/wiki/Future_of_Earth
I submit that this is probably Earth's only chance at a spacefaring civilization, and therefore Earth life's only chance at escaping the planet (and thus surviving the death of the planet). If we flub it and cause a mass extinction without anything to show for it, it is the beginning of the end of Earth's story.
It's worth noting that the Earth's atmosphere would be incompatible with current life at various past levels of atmospheric carbon.
In the past, Earth's atmosphere was almost entirely nitrogen and carbon dioxide[1], but at some point some plucky cyanobacteria learned how to photosynthesize and convert CO2 into O2, hugely changing the contents of the atmosphere [2] and killing a large amount of life that couldn't tolerate the new order.
So if we were to burn all the fossil fuels, it's quite possible that this would cause a climate catastrophe that would kill a large majority of life on earth. But there's a decent chance that the cyanobacteria and friends would survive and, after hundreds of millions of years, restart the evolutionary process.
Note that climate catastrophes take many forms, and the "greenhouse effect" does not even necessarily have to be involved. Take ocean acidification for instance. Atmospheric carbon raises the pH level of the ocean, which can cause cascading ecological collapse.
[1] https://en.wikipedia.org/wiki/Paleoclimatology
[2] https://en.wikipedia.org/wiki/Great_Oxidation_Event
[3] https://en.wikipedia.org/wiki/Ocean_acidification