RE: "Turning point in history"30 May 2021 15:10
When more CO2 is released from outside of the natural carbon cycle – by burning fossil fuels.
" Although anthropogenic output of 29 gigatons of CO2 is tiny compared to the 750 gigatons moving through the carbon cycle each year, it adds up because the land and ocean cannot absorb all of the extra CO2. About 40% of this additional CO2 is absorbed. The rest remains in the atmosphere, and as a consequence, atmospheric CO2 is at its highest level in 15 to 20 million years (Tripati 2009). (A natural change of 100ppm normally takes 5,000 to 20,000 years. The recent increase of 100ppm has taken just 120 years)"
https://climate.nasa.gov/vital-signs/carbon-dioxide/