Human activities release far more carbon dioxide than volcanoes do

Key takeaway

It's true that carbon dioxide is among the gases emitted by volcanic activity. However, it's clear from several lines of evidence that human activities are producing far more carbon dioxide, and volcanoes are not responsible for the observed increase in greenhouse gases.

Reviewed content

Verdict:

Inaccurate

Claim:

That one little burp by Mt. Etna has already put more than 10,000 times the CO2 into the atmosphere than mankind has in our entire time on the Earth

Verdict detail

Factually inaccurate: Each year, humans emit far more CO₂ than all eruptions around the world combined.

See our method of evaluation

Full Claim

That one little burp by Mt. Etna has already put more than 10,000 times the CO2 into the atmosphere than mankind has in our entire time on the Earth but don't worry, a scam is in the works to tax you for your miniscule footprint…

Carbon dioxide is released into the atmosphere by volcanic eruptions—as well as by passive venting around volcanoes that are not erupting. The amount of CO₂ emitted varies from one volcanic feature to another, and varies with time, which makes quantifying global emissions a challenge. However, there are multiple ways of constraining their contribution.

The most recent estimate¹ puts total global emissions from all volcanic activity at approximately 280 million to 360 million metric tons of CO₂ per year. Of this, active eruptions only account for about 2 million metric tons per year. Additionally, there is no evidence that volcanic activity has increased over the last century, while atmospheric CO₂ has increased significantly.

Human-caused CO₂ emissions are much larger than this estimate. Current emissions from fossil fuel burning, industrial processes, and land use change (like deforestation) equal about 39 billion metric tons per year²—at least 100 times greater than the amount released by all volcanic activity, let alone eruptions.

Prior to human-caused emissions, Earth’s carbon cycle was in balance. The amount of CO₂ released by things like volcanoes, wildfires, and respiration by living things was equal to the amount of atmospheric CO₂ taken up by processes like bedrock weathering and photosynthesis. Human-caused emissions are not matched by a human-caused process of CO₂ uptake, so this net addition is responsible for the observed increase in atmospheric CO₂ since the Industrial Revolution.

In addition to these accounting methods for estimating the factors related to the atmospheric CO₂ concentration, the source of the CO₂ added to the atmosphere can also be determined from the isotopes of carbon in the air. Because the carbon atoms in volcanic CO₂ have a different isotope ratio than the carbon atoms in fossil fuel CO₂, the measured change in atmospheric carbon-14, carbon-13, and carbon-12 shows that the CO₂ added to the atmosphere has come from fossil fuel burning and deforestation—not volcanoes³.

• 1- Werner et al (2019) Carbon Dioxide Emissions from Subaerial Volcanic Regions (in Deep Carbon, Past to Present)
• 2- Le Quéré et al (2018) Global Carbon Budget 2018, Earth System Science Data
• 3- Rubino et al (2013) A revised 1000 year atmospheric δ13C‐CO2 record from Law Dome and South Pole, Antarctica, Journal of Geophysical Research: Atmospheres

Tobias Fischer

Professor, University of New Mexico

The contribution of volcanoes to the global carbon dioxide (CO₂) emissions budget is small^1-16 compared to the emission from burning of fossil fuels¹⁷. In detail, the contribution of volcanic eruptions can be illustrated by considering recent, well-studied large eruptions, such as the 2014 Holhuraun eruption in Iceland.

The massive Holhuraun eruption emitted a cumulative amount of 9,330 kilotons of CO₂ (or 9.3 x10¹² g CO₂)¹⁸. The eruption of Etna Volcano in Italy in the year 2006 emitted a cumulative CO₂ amount of 644 kilotons (or 0.644 x 10¹² g CO₂). Another recent and massive eruption was the 2010 Eyjaflallajokul eruption in Iceland that emitted a cumulative amount of CO₂ of 5,130 kilotons (or 5.1 x 10¹² g CO₂)¹⁸. While these eruptions have significantly affected local air travel and disrupted the daily lives of the population living in the region, the amount of CO₂ emitted is dwarfed by the emissions resulting from human activities.

The burning of fossil fuels and production of cement has released 36.3 gigatons of CO₂ (or 36,300 x 10¹² g CO₂) into the atmosphere in 2015¹⁷. Therefore, the largest CO₂ emitting eruption in the past 15 years (Holhuraun in 2014) produced only about 0.026% of the yearly anthropogenic emissions. Indeed, we would need to have about 3,890 such massive eruptions like Holhuraun in one year to produce the equivalent of CO₂ emitted due to fossil fuel burning and cement production. However, such large CO₂ emitting eruptions are rare and the Holuhraun 2014 eruption is unique in the past 15 years¹⁸.

The total CO₂ emissions for volcanic eruptions for the time frame from 2005 to 2018 was 26.9 megatons (or 26.0 x 10¹² g CO₂) and, therefore, in an average year only about 2,070 kilotons of CO₂ (or 2.0 x 10¹² g) are produced from volcanic eruptions¹⁸. This means that, during a typical year, volcanic eruptions contribute only about 0.006% of the global anthropogenic CO₂ flux.  The average CO₂ emission of a person living in the USA is about 16 tons of CO₂ per year¹⁷. Therefore, in any given year volcanic eruptions produce only about as much CO₂ as 130,000 Americans, or less than the population of Wyoming—the state with the lowest population in the US.

• 1- Aiuppa et al (2019) CO₂ flux emissions from the Earth’s most actively degassing volcanoes, 2005–2015, Scientific Reports
• 2- Allard (1992) Global Emissions of helium-3 by subareal volcanism, Geophysical Research Letters
• 3- Brantley and Koepenick (1995) Measured carbon dioxide emissions from Oldoinyo Lengai and the skewed distribution of passive volcanic fluxes, Geology
• 4- Burton et al (2013) Deep carbon emissions from volcanoes, Reviews in Mineralogy and Geochemistry: Carbon in Earth
• 5- Fischer (2008) Volatile fluxes (H₂O, CO₂, N₂, HCl, HF) from arc volcanoes , Geochemical Journal
• 6- Gerlach (1991) Present-day CO₂ emissions from volcanoes, EOS Transactions
• 7- Hilton et al (2002) Noble gases in subduction zones and volatile recycling, MSA Special Volume: Noble Gases in Geochemistry and Cosmochemistry
• 8- Kerrick (2001) Present and past nonanthropogenic CO₂ degassing from the solid earth, Reviews of Geophysics
• 9- Le Guern (1982) Les debits de CO₂ et de SO₂  volcaniques dans l’atmosphere. Translated title: Discharges of volcanic CO₂  and SO₂  in the  atmosphere, Bulletin of Volcanology
• 10- Williams et al (1992) Global carbon dioxide emission to the atmosphere by volcanoes, Geochimica et Cosmochimica Acta
• 11- Marty et al (1989) Helium isotopes and CO2 in volcanic gases of Japan, Chemical Geology
• 12- Marty and LeCloarec (1992) Helium-3 and CO₂ fluxes from subaereal volcanoes estimated from Polonium-20 emissions, Journal of Volcanology and Geothermal Research
• 13- Marty and Tolstikhin (1998) CO₂ fluxes from mid-ocean ridges, arcs and plumes, Chemical Geology
• 14- Moerner and G. Etiope (2002) Carbon degassing from the lithosphere, Global and Planetary Change
• 15- Sano and Williams (1996) Fluxes of mantle and subducted carbon along convergent plate boundaries, Geophysical Research Letters
• 16- Shinohara (2013) Volatile fluxes from subduction zone volcanoes: insights from a detailed evaluation of the fluxes from volcanoes in Japan, Journal of Volcanology and Geothermal Research
• 17- Le Quéré et al (2016), Global Carbon Budget 2016, Earth System Science Data
• 18- Werner et al (2019) Carbon Dioxide Emissions from Subaerial Volcanic Regions (in Deep Carbon, Past to Present)

UPDATES

• 4 November 2019: This post was updated to include a comment by Tobias Fischer.