evidence: Before the Industrial Revolution, naturally-occurring amounts of greenhouse gases caused the air near the surface to be about 33 °C warmer than it would have been in their absence.[118][119] Human activity since the Industrial Revolution, mainly extracting and burning fossil fuels (coal, oil, and natural gas),[120] has increased the amount of greenhouse gases in the atmosphere, resulting in a radiative imbalance. In 2019, the concentrations of CO2 and methane had increased by about 48% and 160%, respectively, since 1750.[121] These CO2 levels are higher than they have been at any time during the last 2 million years. Concentrations of methane are far higher than they were over the last 800,000 years.[122] [...] - ^ a b Our World in Data, 18 September 2020 - ^ IPCC AR6 WG1 Technical Summary 2021, p. 67: "Concentrations of CO2, methane (CH4), and nitrous oxide (N2O) have increased to levels unprecedented in at least 800,000 years, and there is high confidence that current CO2 concentrations have not been experienced for at least 2 million years."