The 12% portion of carbon dioxide which has no carbon-14 left in it is old, not new.
While alive, organisms breathe in a mix of carbon-12 (normal) and carbon-14. This is because cosmic rays create some carbon-14 which then gets ingested by living organisms -- but after you die, you stop ingesting it totally.
Every 5,700 years, another half of the "ingested-while-alive" carbon-14 is decayed out of dead tissue. Fossil fuels come from things that lived over 65 million years ago though, so that essentially all of their carbon-14 is gone by now.
Some of that 12% atmospheric co2 that carbon dates to the last few hundred years will also be from natural sources like wildfires etc.
Stats show less wildfires nowadays than in the past but they destroy huge amounts of growing land and likely liberate carbon in the soil too.
Using carbon dating you can’t separate co2 from Forrest fires from co2 from fossil fuels. .
The 12% portion of carbon dioxide which has no carbon-14 left in it is old, not new.
While alive, organisms breathe in a mix of carbon-12 (normal) and carbon-14. This is because cosmic rays create some carbon-14 which then gets ingested by living organisms -- but after you die, you stop ingesting it totally.
Every 5,700 years, another half of the "ingested-while-alive" carbon-14 is decayed out of dead tissue. Fossil fuels come from things that lived over 65 million years ago though, so that essentially all of their carbon-14 is gone by now.