Humans Create More Atmospheric Carbon Dioxide Than Volcanoes Do

January 24, 2023 5:44 am40 commentsViews: 98

Within the din of discussion about the source of carbon dioxide (the gas that is very likely the principal cause of current global warming) that is being added to Earth’s atmosphere is the undocumented opinion of some that the amount of carbon dioxide released by active volcanoes and their shallow magmatic (magma is molten rock that feeds volcanic eruptions) roots far outstrips the amount created by human combustion of fossil fuels.

Humans Create More Atmospheric Carbon Dioxide Than Volcanoes Do

Scientists who measure the amount of carbon dioxide released by volcanoes and their magmatic roots have long known that the opposite is true. In fact, the most recent summary of such research indicates that the current average annual release of carbon dioxide from human activities is about 135 times greater than that from volcanoes.

Volcanic Carbon Dioxide

Many independent studies by several volcano-scientist teams have determined the annual amount of carbon dioxide released by volcanoes. Though the bottom-line is not the same from team to team, all fall within the range of 0.13 to 0.44 gigatons per year.

The spread of results reflected by this range arises from uncertainties in defining the average annual volume of erupted magma and the amount of carbon dioxide that was originally dissolved in that magma and thus released during eruption.

Nonetheless, both of these uncertainties are constrained closely enough, by field and laboratory data, to confidently define the 0.13 to 0.44 gigaton range. The value assessed by the researchers to most nearly reflect the actual situation is 0.26 gigatons per year.

Even at the high end of 0.44 gigatons per year, the annual amount of anthropogenic carbon dioxide far exceeds that from volcanoes.

Anthropogenic Carbon Dioxide

During the year 2010, the amount of anthropogenic carbon dioxide was 35 gigatons, created mostly by burning of fossil fuels. There is very little uncertainty in this number, because the amounts of fossil fuels burned (tons of coal, gallons of petroleum, etc.) and the resultant carbon dioxide combustion product are well known.

The annual mass of carbon dioxide produced by human activities each year has increased steadily during the twentieth century and on forward to the present time. The annual rate of increase has risen through time as a growing human population has consumed fossil fuel at a steady-per-person, or more likely at an accelerating-per-person rate.

During 1900, anthropogenic carbon dioxide was about 18 times that from volcanoes. During 1950 it was about 38 times that from volcanoes. Thereafter it rose rather rapidly to today’s value of about 135, relative to an average annual volcanic contribution of 0.26 gigatons per year.

The Effect of Unusually Large Volcanic Eruptions

Those who believe that volcanoes produce more carbon dioxide than human activities often highlight the massive outpourings of this gas during especially large volcanic eruptions.

In fact, a large eruption, such as that at Mount St. Helens of Washington State in 1980 or that at Pinatubo in the Philippines in 1991, released carbon dioxide at a rate that would in fact total to about 35 gigatons per year (the value for the 2010 anthropogenic carbon dioxide), if eruption had lasted an entire year. However, each of these eruptions lasted only hours to a few days.

Volcanoes such as these, and their even larger-volume counterparts, remain dormant for centuries or longer between eruptions. So even though they produce a very brief spike in new atmospheric carbon dioxide, over longer periods of time their carbon dioxide production is dwarfed by that of the continuous, day-to-day anthropogenic inputs.

All active volcanoes add carbon dioxide to Earth’s atmosphere, but at an annual rate that is far far less than that attributable to the human burning of fossil fuels.


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