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Do volcanoes emit more CO2 than humans?

What the science says...

Select a level... Basic Intermediate

Humans emit 100 times more CO2 than volcanoes.

Climate Myth...

Volcanoes emit more CO2 than humans

"Human additions of CO2 to the atmosphere must be taken into perspective.

Over the past 250 years, humans have added just one part of CO2 in 10,000 to the atmosphere. One volcanic cough can do this in a day." (Ian Plimer)

The solid Earth contains a huge quantity of carbon, far more than is present in the atmosphere or oceans.  Some of this carbon is slowly released from the rocks in the form of carbon dioxide, through vents at volcanoes and hot springs. Volcanic emissions are a small but important part of the global carbon cycle. Published reviews of the scientific literature by Mörner & Etiope (2002) and Kerrick (2001) report a range of emission of 65 to 319 million tonnes of CO2 per year. Counter claims that volcanoes, especially submarine volcanoes, produce vastly greater amounts of CO2 than these estimates are not supported by any papers published by the scientists who study the subject. 

The burning of fossil fuels and changes in land use results in the emission into the atmosphere of approximately 34 billion tonnes of carbon dioxide per year worldwide, according to the U.S. Energy Information Administration (EIA). The fossil fuels emissions numbers are about 100 times bigger than even the maximum estimated volcanic CO2 fluxes. Our understanding of volcanic discharges would have to be shown to be very mistaken before volcanic CO2 discharges could be considered anything but a bit player in contributing to the recent changes observed in the concentration of CO2 in the Earth's atmosphere.

Volcanoes can—and do—influence the global climate over time periods of a few years but this is achieved through the injection of sulfate aerosols into the high reaches of the atmosphere during the very large volcanic eruptions that occur sporadically each century. But that's another story...

Recommended further reading on CO2 and volcanoes can be found here: Terry Gerlach in Earth Magazine ; USGS

Last updated on 2 June 2017 by John Cook. View Archives

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Further reading

Tamino has posted two examinations of the "volcanoes emit more CO2 than humans" argument by looking at the impact of the 1991 Pinutabo eruption on CO2 levels and the impact of past super volcanoes on the CO2 record.

The Global Volcanism Program have a list of all volcanoes with a Volcanic Explosivity Index (VEI) greater than 4 over the past 10,000 years.

Myth Deconstruction

Related resource: Myth Deconstruction as animated GIF

MD Volcano

Please check the related blog post for background information about this graphics resource.


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Comments 301 to 308 out of 308:

  1. One can also look at the ice core CO2 data and isolate the rate of change per unit time, as a method to isolate slug inputs to the atmosphere from carbon reservoirs.

    Here's a personal try:

    CO2 vs the natural range

  2. The new estimates of volcanic emissions are around 50 million tons per year (Wong et al. 2019), lower than the low estimate in this article. Here is a graph I just made comparing cumulative human emissions to global biomass and cumulative volcanic emissions over the same time period: CO2 comparison.

  3. Someone I was debating on twitter (I know not a good idea) claims that quote "Out gassing via leakage and fumaroles under the ocean floors and from "quiet" volcanoes and thousands of miles of mid oceanridge" is a significant contribution to CO2 emissions.  I'm v.skeptical of this and wondered if anyone else had heard this or had recent estimates for global ocean floor out-gassing from ridges, ocean volcanos and fumaroles.  I suspect he is missing geological CO2 sinks

  4. jon_zz09... My understanding is that, any CO2 emitted from underwater volcanoes would be dissolved before reaching the surface. That could be a complicating factor for ocean acidification, but it does nothing to explain the rapid rise in atmospheric concentrations starting with the industrial revolution.

  5. jon_zz09 - the killer for that argument is the volcanic CO2 has very different C isotopic signature to that fossil fuels. The changes in atmospheric C isotopic composition are consistant with FF source. Furthermore, the studies referenced in this article (and see more here) account for submarine volcanoes. While estimation is difficult even the high end of the estimates is small compared to FF emissions. Finally, there is no evidence of an increase in volcanism as Rob says ( see here from Global Volcanism Program).

  6. Here's what the peer-reviewed published literature shows, that humans produce 100x more CO2 than all Earth's volcanoes combined:

    - Just two-one thousandths* of 1% of Earth's total carbon—about 43,500 gigatonnes (Gt)—is above surface in the oceans, on land, and in the atmosphere. The rest is subsurface, including the crust, mantle and core—an estimated 1.85 billion Gt in all.

    - CO2 out-gassed to the atmosphere and oceans today from volcanoes and other magmatically active regions is estimated at 280 to 360 million tonnes (0.28 to 0.36 Gt) per year, including that released into the oceans from mid-ocean ridges.

    - Humanity’s annual carbon emissions through the burning of fossil fuels and forests, etc., are 40 to 100 times greater than all volcanic emissions.

    - Earth’s deep carbon cycle through deep time reveals balanced, long-term stability of atmospheric CO2, punctuated by large disturbances, including immense, catastrophic releases of magma that occurred at least five times in the past 500 million years. During these events, huge volumes of carbon were outgassed, leading to a warmer atmosphere, acidified oceans, and mass extinctions.

    - Similarly, a giant meteor impact 66 million years ago, the Chicxulub bolide strike on Mexico’s Yucatan peninsula, released between 425 and 1,400 Gt of CO2, rapidly warmed the planet and coincided with the mass (>75%) extinction of plants and animals—including the dinosaurs. Over the past 100 years, emissions from anthropogenic activities such as burning fossil fuels have been 40 to 100 times greater than our planet’s geologic carbon emissions.

    - A shift in the composition of volcanic gases from smelly (akin to burnt matches) sulphur dioxide (SO2) to a gas richer in odorless, colorless CO2 can be sniffed out by monitoring stations or drones to forewarn of an eruption—sometimes hours, sometimes months in advance. Eruption early warning systems with real-time monitoring are moving ahead to exploit the CO2 to SO2 ratio discovery, first recognized with certainty in 2014.

    Regarding the release of CO2 from volcanoes:

    "Earth’s total annual out-gassing of CO2 via volcanoes and through other geological processes such as the heating of limestone in mountain belts is newly estimated at roughly 300 to 400 million metric tonnes (0.3 to 0.4 Gt).

    Volcanoes and volcanic regions alone outgas an estimated 280–360 million tonnes (0.28 to 0.36 Gt) of CO2 per year. This includes the CO2 contribution from active volcanic vents, from the diffuse, widespread release of CO2 through soils, faults, and fractures in volcanic regions, volcanic lakes, and from the mid-ocean ridge system."

    Kelemen and Manning 2015 - Reevaluating carbon fluxes in subduction zones, what goes down, mostly comes up

    de Moor et al 2016 - Short-period volcanic gas precursors to phreatic eruptions: Insights from Poás Volcano, Costa Rica

    McCormick et al 2016 - Observing eruptions of gas-rich, compressible magmas from space

    Johansson et al 2018 - The Interplay Between the Eruption and Weathering of Large Igneous Provinces and the Deep‐Time Carbon Cycle

    Tamburello et al 2018 - Global-scale control of extensional tectonics on CO2 earth degassing

    Lee et al 2019 - A Framework for Understanding Whole-Earth Carbon Cycling

    Black and Gibson 2019 - Deep Carbon and the Life Cycle of Large Igneous Provinces

    Kamber and Petrus 2019 - The Influence of Large Bolide Impacts on Earth’s Carbon Cycle

    "pCO2 is a result of the balance between the rate of CO2 inputs through magmatic/metamorphic degassing and the rates of carbon removal via silicate weathering and organic carbon burial."

    McKenzie and Hehe Jiang 2019 - Earth’s Outgassing and Climatic Transitions_The Slow Burn Towards Environmental Catastrophes

    Mikhail and Furi 2019 - On the Origins and Evolution of Earth’s Carbon

    Schobben et al 2019 - Interpreting the Carbon Isotope Record of Mass Extinctions

    Suarez et al 2019 - Earth Catastrophes and Their Impact on the Carbon Cycle

    Werner et al 2019 - Carbon Dioxide Emissions from Subaerial Volcanic Regions_Two Decades in Review

    "All studies to date of global volcanic carbon dioxide emissions indicate that present-day subaerial and submarine volcanoes release less than a percent of the carbon dioxide released currently by human activities. "

  7. Thanks guys, very helpful.  Yes the difference is huge I knew it was for land volcanoes and suspected the ocean activity wasn't significant, great to have the useful sources to confirm, also found the Wong 2019 from above useful.

  8. Respectfully,  I believe we're all missing the point. 

    I don't care if global warming is occurring and I care even less if it's human activity that the culprit. If we don't like CO² (I like CO², because it increases crop yields in a hungry world),  then either live like a caveman and don't use fossil fuels or go nuclear (my preferred option). Clearly solar and wind are not the answer. Insulation and self denial are not the answer. These just assist in reducing energy.  (Improving the aerodynamics of a car is pointless, if there's no engine). 

    We need less people on the planet and - most of all - less politicians)


    [DB] The topic of this post is about how human activities release vastly more greenhouse gases into the active carbon cycle than do al the volcanoes on Earth combined.  Please stay on-topic.  Off-topic snipped.

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