- ---. Climate Change: Atmospheric Carbon Dioxide. National Oceanic and Atmospheric Administration (NOAA), 10 July 2021, https://www.climate.gov/news-features/understanding-climate/climate-change-atmospheric-carbon-dioxide.
- ---. “Carbon Dioxide Concentration”. Global Climate Change: Vital Signs of the Planet, https://climate.nasa.gov/vital-signs/carbon-dioxide. Accessed 28 Dec. 2021.
- ---. “Doesn’t Carbon Dioxide in the Atmosphere Come from Natural Sources?”. NOAA Climate.Gov, 29 Oct. 2020, https://www.climate.gov/news-features/climate-qa/doesnt-carbon-dioxide-atmosphere-come-natural-sources.
- “Climate Change: Evidence and Causes: CO2 Is Already in the Atmosphere Naturally, so Why Are Emissions from Human Activity Significant?”. Royal Society, Mar. 2020, https://royalsociety.org/topics-policy/projects/climate-change-evidence-causes/question-3/.
- “Daily CO2”. CO2.Earth, https://www.co2.earth/daily-co2. Accessed 28 Dec. 2021.
- Jones, Nicola. “How the World Passed a Carbon Threshold and Why It Matters”. Yale E360, Jan. 2017, https://e360.yale.edu/features/how-the-world-passed-a-carbon-threshold-400ppm-and-why-it-matters.
- Observatory, Deep Carbon. “Scientists Quantify Global Volcanic CO2 Venting; Estimate Total Carbon on Earth”. Phys.Org, 10 Jan. 2019, https://phys.org/news/2019-10-scientists-quantify-global-volcanic-co2.html.
- Schwarcz, Joe. “Why Isn’t the Carbon Dioxide from Breathing a Concern for Global Warming?”. McGill Office for Science and Society, 20 Mar. 2017, https://www.mcgill.ca/oss/article/environment-quirky-science-you-asked/humans-and-animals-exhale-carbon-dioxide-every-breath-why-not-considered-be-problem-far-global.
- “The Carbon Cycle - The Carbon Cycle and Decomposition (CCEA)”. BBC Bitesize, https://www.bbc.co.uk/bitesize/guides/zg6t2nb/revision/2. Accessed 28 Dec. 2021.
- United States Environmental Protection Agency. “Climate Change Indicators: Atmospheric Concentrations of Greenhouse Gases”. United States Environmental Protection Agency, 27 June 2016, https://www.epa.gov/climate-indicators/climate-change-indicators-atmospheric-concentrations-greenhouse-gases.
- van der Werf, Guido R., et al. “Global Fire Emissions Estimates during 1997–2016”. Earth System Science Data, vol. 9, no. 2, Sept. 2017, pp. 697–720. DOI.org (Crossref), https://doi.org/10.5194/essd-9-697-2017.