Evidence from changing 13C/12C isotopic ratio for human generated increases in carbon dioxide

This video draws on three studies (below) investigating how the changing ratio of carbon C-13/C-12 isotopes in the atmosphere since the beginning of industrialization correlates to the dramatic rise in CO2 concentration in the earth's atmosphere:
"Natural and anthropogenic changes in atmospheric CO2 over the last 1000 years from air in Antarctic ice and firn" D. M. Etheridge, et al., Journal of Geophysical Research, Volume. 101, No. D2, Pages 4115-4128, Februrary 20, 1996 https://www.rescuethatfrog.com/wp-con...
"A 1000-year high precision record of δ13C in atmospheric CO2" R. J. Francey, et al., Tellus B: Chemical and Physical Meteorology, Volume 51B, 170–193, 1999 https://www.tandfonline.com/doi/pdf/1...
"Long-term variability in the global carbon cycle inferred from a high-precision CO2 and δ13C ice-core record" C. M. Trudinger, et al., Tellus B: Chemical and Physical Meteorology, Volume 51, 233-248, 1999 - Issue 2 https://www.tandfonline.com/doi/abs/1...