How do scientists know human activities are the cause?
A number of factors clearly point to the role of human activities as the primary source of increases in greenhouse gas (GHG) concentrations in the atmosphere. The rapid rise in GHG concentrations during the past century is consistent with trends in human emissions. The relative abundance of CO2 molecules in the atmosphere containing the radioactive carbon 14 atom is declining. This is consistent with increased concentrations from the burning of coal, oil and natural gas, all of which contain ‘old’ carbon without carbon 14. Changes in the proportion of carbon 13 and carbon 12 in oceans are also consistent with human emissions. READ MORE ..
