And we know it's humans who made the increase of CO2 from the measurements of the carbon isotopes in the ice cores, which stored the state of the air from the e

And we know it's humans who made the increase of CO2 from the measurements of the carbon isotopes in the ice cores, which stored the state of the air from the earlier times. Human burning of the fossil fuels changes the isotope ratio exactly: it is certain that just humans, burning the fossil fuels, are those who change the CO2 concentration through the years.