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Volcanic CO2 emissions are known to be much smaller than human-caused emissions

CLAIM
Discovery Of Massive Volcanic CO2 Emissions Discredits Global Warming Theory
VERDICT more about the rating framework
DETAILS
Factually Inaccurate: Scientists have established that volcanic emissions are small compared to human-caused emissions.
KEY TAKE AWAY
This article claims that volcanic sources of carbon dioxide are poorly understood and could well be the cause of modern global warming, rather than human activities. In reality, current annual human-caused emissions are at least 100 times greater than all volcanic emissions.

REVIEW

CLAIM: Discovery Of Massive Volcanic CO2 Emissions Discredits Global Warming Theory [...] All indications are that Earth is currently experiencing another period of strong volcanic activity which is acting to infuse CO2 into our atmosphere thereby challenging the validity of the global warming theory.

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.

graphic showing movement of carbon around the carbon cycle

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. Contrary to the claim in the article, the carbon atoms in volcanic CO2 do have a different isotope ratio than the carbon atoms in fossil fuel CO2.  In fact, the very source the article links to support its claim actually explains this. 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 volcanoes or other sources3.

Tobias Fischer, Professor, University of New Mexico:
The contribution of volcanoes to the global carbon dioxide (CO2) emissions budget is small1-16 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.

 

Published on: 03 Jan 2020 | Editor:

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