CO2 from human activity far surpasses that of volcanoes

Human activity produces more CO2 in three to five days than all volcanoes produce in a year, according to study.

In just three to five days, human activities create about the amount of carbon dioxide – a greenhouse gas linked to climate change – that volcanoes produce globally in a year, according to Terrance Gerlach of the U.S. Geological Survey.

Gerlach reviewed five published studies of present-day global volcanic carbon dioxide emissions and compared those emissions to anthropogenic (human-induced) carbon dioxide output. An article by Gerlach appears in the June 14, 2011 issue of Eos, a weekly publication of the American Geophysical Union.

Gerlach said:

The most frequent question that I have gotten (and still get) in my 30-some years as a volcanic gas geochemist – from the general public and from geoscientists working in fields outside of volcanology – is “Do volcanoes emit more carbon dioxide than human activities?” Research findings indicate unequivocally that the answer to this question is “No” – anthropogenic carbon dioxide emissions dwarf global volcanic carbon dioxide emissions.

Image Credit: Cyrus Read, USGS

Gerlach looked at studies showing a range of results for volcanic carbon dioxide emissions, from one-tenth of a billion to half a billion metric tons of carbon dioxide per year. He based his comparisons on the figure of one-quarter of a billion metric tons. The estimated carbon dioxide emission rate from human activity for 2010 was approximately 35 billion metric tons.

Gerlach’s calculations suggest that present-day anthropogenic carbon dioxide emissions may annually exceed the carbon dioxide output of one or more super eruptions. As he notes in the Eos article:

Super eruptions are extremely rare, with recurrence intervals of 100,000-200,000 years; none has occurred historically, the most recent examples being the Toba eruption 74,000 years ago in Indonesia and the Yellowstone caldera eruption in the United States 2 million years ago.

Although geoscientists continue in their efforts to improve estimates and reduce uncertainties about how much carbon dioxide is released from mid-ocean ridges, from volcanic arcs and from hot-spot volcanoes, agreement exists among volcanic gas scientists regarding the significantly smaller emissions of volcanic carbon dioxide compared to anthropogenic carbon dioxide.

Bottom line: Terrance Gerlach of the U.S. Geological Survey reviewed five published studies of present-day global volcanic carbon dioxide emissions and compared those emissions to anthropogenic (human-induced) carbon dioxide output. He concluded that in just three to five days, human activity creates the amount of carbon dioxide that volcanoes produce globally each year. The June 14, 2011 issue of Eos published his article.

American Geophysical Union

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