How certain are scientists that increased carbon dioxide is caused by humans?

Scientists are highly certain that increased carbon dioxide levels in the atmosphere are primarily caused by human activities, particularly the burning of fossil fuels and deforestation. Extensive research, including analysis of carbon isotopes, shows that the rise in CO2 correlates with industrialization since the 18th century. The Intergovernmental Panel on Climate Change (IPCC) and numerous studies affirm that the current rate of CO2 increase is unprecedented in at least 800,000 years and is largely attributed to human actions.