Burning Fossile fuel isn't just producing CO2 it's also allowing us to create fertilizers that keep 3B people alive, it's allowing us to produce cement, steel and plastic all of them the foundation of modern civilisation. Many of us wouldn't be alive if it wasn't for that.
On top of that it's what allow us to have machine do heavy work instead of humans, freeing more people up to do other things than working in the fields, which among other things gave us the internet which we are currently using, or many types of medicine, hell you can can't even do wind and solar without using fossil fuels.
So if we want to start counting externalities lets do that. But let do it fairly and it should be pretty clear that the positive externalities far outweigh the negative ones, which is why it's 80% of our energy consumption to this day.
But there is a simple experiment you can do.
List all the things you can't live without. List if they are possible without CO2 For those that aren't list if it's possible with current technologies, and current economics and current knowledge to create alternatives that are matching.
You will quickly realize you can't do that unless you are contempt with living like natives in some far remote jungle or with inferior or much more expensive solutions ( which then create its own set of externalities)
It wouldnt work to make a net calculation with its costs?