Doesn't carbon dioxide in the atmosphere come from natural sources?

January 23, 2014

There are natural sources of carbon dioxide, such as decomposing biomass, venting volcanoes, naturally occurring wildfires, human and animal respiration, etc. Over geological time spans before the industrial revolution, these natural sources of carbon dioxide were in balance with natural "sinks"—such as the ocean, phytoplankton, and plants on land that absorb carbon dioxide. The only new process on Earth that has been identified that can account for the significant tipping of Earth's carbon balance is humans burning ever increasing amounts of fossil fuels together with other large-scale activities like deforestation, biomass burning, and cement production. Since the industrial revolution, human activities have increased the abundance of carbon dioxide in the lower atmosphere by about 40%.

Lightning-sparked wildfire

Lightning-sparked fires, such as the Douglas County Complex Fire in Washington State in 2015, can release carbon dioxide, but human activity produces much more of the greenhouse gas. Photo CC license by USDA.


IPCC (2007): Climate Change 2007: The Physical Science Basis. Contribution of Working Group 1 to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor, and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 996 pp.

Tans, P. and R. Keeling: "Trends in Atmospheric Carbon Dioxide." Online at (Accessed July 2013.)