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USGS scientist concludes that anthropogenic CO2 emissions dwarf those from volcanoes

On average, human activities put out in just three to five days the equivalent amount of carbon dioxide that volcanoes produce globally each year, according to Terrance Gerlach of the US Geological Survey (USGS). Gerlach based his findings on a review of five published studies of present-day global volcanic carbon dioxide emissions, which he then compared to anthropogenic (human-induced) carbon dioxide output.

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.

—Terrance Gerlach

Gerlach’s findings are detailed in an article published today in Eos, the weekly newspaper of the Earth and space sciences. The article is publicly available for download. Eos is a publication of the American Geophysical Union.

The studies reviewed by Gerlach give a range of results for volcanic carbon dioxide emissions, from a minimum of about one tenth of a billion to a maximum of about half a billion metric tons of carbon dioxide per year. Gerlach used the figure of about one-quarter of a billion metric tons of volcanic carbon dioxide per year to make his comparisons. The published projected anthropogenic carbon dioxide emission rate for 2010 is about 35 billion metric tons per year. (In US tons—i.e., “short” tons—the above figures are approximately 10 percent greater.)

Gerlach’s calculations suggest present-day annual anthropogenic carbon dioxide emissions may exceed the carbon dioxide output of one or more supereruptions. As he notes in the Eos article, “Supereruptions are extremely rare, with recurrence intervals of 100,000-200,000 years; none have 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.


  • Terry Gerlach, “Volcanic Versus Anthropogenic Carbon Dioxide”; Eos, Vol. 92, No. 24 14 June 2011


Aaron Turpen

Good thing CO2 doesn't do much of anything in the atmosphere other than give plants more stuff to breath. I'm sure tax dollars were wasted on this stupid study.

Henry Gibson

The report should have mentioned all the other non human CO2 releases from plants and animals and micro-organisms. ..HG..


You miss the point.

Without this study we would appoint a volcano czar and award grants for volcano capture and sequester.


"The report should have mentioned all the other non human CO2 releases from plants and animals and micro-organisms."

Plants and animals and micro-organisms only release the CO2 that other plants and animals and micro-organisms had previously taken up and which still other plants and animals and micro-organisms will take in again.

Ultimately all carbon, from whatever source, will be cycled out of the atmosphere. The only real problem is that currently the rate of uptake doesn't match the rate of release.


Typical fallback for the li... er, deniers.

"Volcanoes emit more CO2 than humans do!"

"Hogwash; humans emit roughly 100 times as much as volcanoes."

"Well, it doesn't do anything anyway."


"It would have happened anyway"

"It really does not matter anyway"


"other than give plants more stuff to breath."

Stan Peterson

All of Mankinds annual contribution consist of about 4% of the total CO2 flux. jher fore 96% of the annual flux has nothing to do with Man.


Nature's annual CO2 flux is cyclic, it goes in & out.
Man's annual contribution is one way, we put it in and expect nature to take it out for us.

The problem is the rate differential. Nature took 300,000,000 years to take out the CO2 and put it in the world's fossil fuel store, in just 300 years we've put half of it back. And we did it on a curve (starting out slow and speeding up as we went on).


Mr. Gerlach has the misfortune of working for USGS - which has just in-distinguished itself with a "peer reviewed" paper in Science claiming "late-20th century snowpack reductions are almost unprecedented in magnitude." Of course the data cited IN the paper showed nothing of the sort. And recent snowpacks are 35% above normal.

Possibly the Eos Newspaper that published Mr. Gerlach is more rigorous than Science and the USGS itself. One hopes so since USGS is now batting double digits.


There's been 30 years of reductions vs 2 years of increases - you can start dissing the USGS in 28 years.

Until then...


Er... no, the slop they call a study at USGS/Science refutes its own conclusion. As I said:

"Of course the data cited IN the paper showed nothing of the sort:"

When you look at the actual data from 1935 - 2006 (used by USGS Pederson) the April SWE average (plus or minus 1) is steady with snowpack increases in the last two years.

Looking at the southern cordillera (Colorado) and checking the NRCS SNOTEL Colorado data reveals no change in average SWE from 1935 - 2009:

That debunking basement must be getting pretty musty by now boys...;)


Deniers will continue to claim that tobacco smoking, CO2, black carbon, ultra and fine particles, smoke from diesels, asbestos, heavy smoke from coal fired power plants, 1001 cancer producing chemicals, radiation from power plants etc etc are all good for our health and well being.

It is difficult to imagine this type of behavior in 2011.


That's funny, when I look at those two JPGs I see the cited reductions just fine.

Anyone else want to take a look and post what you think?


Which is why the climate campaign failed so miserably. "Scientists" looking at data and seeing what they want to see - not what is there.

Harvey your list includes real pollutants with the exception of flora fertilizer CO2 which an astronomer from Iowa State insists is bringing on the Apocalypse. An astronomer whose area of study is the CO2 atmosphere on Venus.

What reputable person claims those pollutants are "all good for our health and well being?"


No. I, like the scientists, just know how to plot moving averages & medians.


Guess nobody else sees what outlier ai_vin sees...

Gerlach et al has yet to address the implications of 3,000,000 new volcanoes only recently discovered:


Seeing only requires looking.


Yes, underwater volcanoes emit CO2 too. However, this CO2 is balanced by the carbon sink provided by the newly formed ocean floor from the lava they also release. Consequently, underwater volcanoes have little effect on atmospheric CO2 levels.

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