Terrence Gerlach: Anthropogenic CO2 far exceeds that produced by volcanoes -- even super-volcanoes

ANTHROPOGENIC CO2 FAR EXCEEDS VOLCANIC

by BRYAN WALKER, hot topic, AUGUST 7, 2011

I was a little startled a few weeks back to see in a Waikato Times column written by former National Party MP Michael Cox the extraordinary claim that the 1991 Mt Pinatubo eruption “shot out more greenhouse gases into the atmosphere than the entire human race had emitted in its entire years on Earth.”  I don’t know where he derived this from – no doubt it’s floating around somewhere in the denial world, though even there it seems possible that he misunderstood what he was reading. Anyway it served to support his view that talk of human-caused warming is a Left-inspired crusade to compensate for the collapse of communism! I was able to say in a letter to the paper how ridiculous the Pinatubo statement was, and pretty much everything else he said as well.

Ian Plimer’s book Heaven and Earth claims that “Volcanoes add far more carbon dioxide to the oceans and atmosphere than humans.” Perhaps that was Cox’s source. Plimer obviously still carries weight with those looking for alternatives to climate science, as a recent Herald piece from cartoonist Peter Bromhead revealed. Bromhead’s denialism survived unscathed a flight to New York sitting next to a climate scientist. It was difficult “for a bewildered old cartoonist to try to verbally outrun somebody professionally clued up on his subject.” But he did detect that “my companion’s viewpoint appeared disturbingly contaminated with doctrine that leaned heavily on ideology rather than absolute fact.” And Bromhead had that “admirably comprehensive book” Heaven and Earth as counterweight. “This volume, with thousands of scientific references on every aspect of climate change – through the history of the planet – is a must-read for those bewildered by climate contradictions.”

All of which is a rather circuitous introduction to my purpose in this post to draw attention to a very worthwhile article on volcanic CO₂ emissions. Terry Gerlach, a retired volcanic gas geochemist who worked with the US Geological Survey, has a guest commentary in Real Climate introducing his article Volcanic Versus Anthropogenic Carbon Dioxide, which was published in the American Geophysical Union’s publication Eos, and is now available online. In the article he addresses the widespread misperception that volcanic CO₂ emissions greatly exceed anthropogenic CO₂ emissions. He presents an overview of the subject, using only published peer-reviewed data with a minimum of technical jargon and aimed at a broad readership. I’ve read it and I can confirm its accessibility for the general reader. A few points from it:

Anthropogenic CO₂ emissions were estimated to be responsible for a projected 35 gigatons of CO₂ in 2010. This clearly dwarfs all estimates of the annual present-day global volcanic CO₂ emission rate of around 0.26 gigaton, which Gerlach points out is comparable to the global CO₂ emissions from the flaring of waste gases, or to the CO₂ emissions of nations such as Pakistan (0.18 gigaton), Kazakhstan (0.25 gigaton), Poland (0.31 gigaton), and South Africa (0.44 gigaton). Anthropogenic emissions were projected to be 135 times as great as volcanic emissions in 2010.

Occasional volcanic paroxysms such as Mount Pinatubo in 1991 or Mount St. Helen’s in 1980 may for a few hours equal or even exceed the human output during those same few hours, but “volcanic paroxysms are ephemeral, while anthropogenic CO₂ is emitted relentlessly from ubiquitous sources.” Gerlach considers what would be needed by way of volcanic activity to exceed the CO₂levels due to human activity, and concludes “… the belief that volcanic CO₂exceeds anthropogenic CO₂ implies either unbelievable volumes of magma production or unbelievable concentrations of magmatic CO_2.”  It would take 700 Mt Pinatubo-equivalent volcanic paroxysms annually to match the yearly level of anthropogenic emissions.

Even super-eruptions don’t compare.  He describes them as extremely rare, with recurrence intervals of 100,000–200,000 years; none have occurred historically, the most recent examples being Indonesia’s Toba volcano, which erupted 74,000 years ago, and the United States’ Yellowstone caldera, which erupted 2 million years ago. “[Calculations] strongly suggest that present-day annual anthropogenic CO₂emissions may exceed the CO₂ output of one or more supereruptions every year.”

The article performs a very useful function in gathering and referencing the work that scientists have done on the issue and spelling out the comparisons. In a quiet and restrained way, it underlines just how massive a disruption the human release of fossil fuel CO₂ is to the natural processes by which Earth’s vital carbon cycle is maintained. It’s very difficult to believe that the consequences can’t be severe. The author in conclusion stresses the need for educators, climate change policy makers, the media, and the general public to understand that anthropogenic CO₂ dwarfs volcanic emissions. “Discussions about climate policy can only benefit from this recognition,” is his final sentence. He’d have been justified in using stronger language.

I should also mention a shorter and simpler article by Gerlach published by Earth Magazine last year in which he specifically addressed Plimer’s assertions on the size of volcanic emissions and took them apart.

http://hot-topic.co.nz/anthropogenic-co2-far-exceeds-volcanic/#more-8544

Human activities emit roughly 135 times as much climate-warming carbon dioxide as volcanoes each year

HUMANS DWARF VOLCANOES FOR CO2 EMISSIONS

Human activities generate more of the greenhouse gas in under three days than volcanoes do in a year.

by Jessica Marshall, Discovery News, June 27, 2011 

• Human activities emit roughly 135 times as much climate-warming carbon dioxide as volcanoes each year.
• Volcanoes emit less than cars and trucks, and less, even, than cement production.
• Climate change skeptics have claimed the opposite.

enlarge

The eruption of the Grimsvotn volcano on May 23, 2011 above Iceland. Click to enlarge this image. 
NordicPhotos /Getty Images

Colossal, mind-bogglingly hot and capable of spewing billowing clouds of flight-grounding smoke and searing, molten lava, volcanoes are spectacular displays of the massive forces at work inside our planet. Yet they are dwarfed by humans in at least one respect: their carbon dioxide emissions.

Despite statements made by climate change deniers, volcanoes release a tiny fraction of the amount of carbon dioxide emitted by human activities every year.

In fact, humans release roughly 135 times more carbon dioxide annually than volcanoes do, on average, according a new analysis. Put another way, humans emit in under three days the amount that volcanoes typically release in a year, according to the best estimates of volcanic emissions.

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"The question of whether or not volcanoes emit more CO2 than human activity is one I get more than any question in my email from the general public.' said Terrence Gerlach, a retired volcanologist, formerly with the Cascades Volcano Observatory, part of the US Geological Survey in Vancouver, Wash. Even earth scientists who work in other areas often pose him the question, he said.

To lay out a clear answer, Gerlach compiled the available estimates of CO2 emissions from all global volcanic activity on land and undersea and compared them with estimates for human emissions. He published the compilation in Eos, a publication of the American Geophysical Union.

Researchers estimate the amounts of carbon dioxide released by terrestrial volcanic eruptions by methods including remote sensing or flying through clouds of erupting volcanic gas, and by measuring certain isotope concentrations near undersea volcanoes. Carbon dioxide is dissolved in magma at great depths and is released as the magma rises to the surface.

"A lot of climate skeptics claim that volcanoes emit more CO2 than humans do," Gerlach said. "They never give any numbers, but the fact is you will never be able to find the volcanic gas scientist that will agree to that," he said.

One example of these skeptics' claims is the 2009 book, "Heaven and Earth: Global Warming, the Missing Science" by Ian Plimer of the University of Adelaide, who did not respond to Discovery News' requests for comment.

DNEWS VIDEO: Could humans MAKE a volcano erupt? Get that answer and more.

"The main reason, I think, that this myth persists," Gerlach said: "First of all, the emissions are extremely spectacular. When people see volcanic eruptions on television and it's awesome, and it's very easy for people to imagine that huge amounts of CO2 are being emitted to the atmosphere."

"However, these spectacular volcanic explosions that are so stunning on TV last only a few hours," he added. "They are ephemeral. In contrast, the sources of anthropogenic CO2 (smokestacks, exhaust pipes, etc) are comparatively unspectacular, commonplace, and familiar, and in addition they are ubiquitous, ceaseless, and relentless. They emit CO2 24/7."

While there is uncertainty in the measurements--researchers estimate between 0.13 and 0.44 billion metric tons per year, with their best estimates between 0.15 and 0.26 billion tons -- even the highest end of the range is dwarfed by anthropogenic emissions of 35 billion metric tons in 2010.

Gerlach noted that human land-use changes alone, which include deforestation, release 3.5 billion metric tons per year. Cars and light-duty trucks produce 2 billion metric tons; even cement production produces 1.5 billion tons. Any of these by itself is still several times higher than the annual emissions of all of the world's volcanoes .

Pakistan or Kazakhstan each produce about the amount of CO2 as volcanoes do each year, Gerlach noted in the article.

In yet another comparison, Gerlach reported that in order for volcanic emissions to match those made by humans, the May 18, 1980, Mount St. Helens eruption would need to happen every 2.5 hours. The June 15, 1991, Mount Pinatubo eruption would need to occur every 12.5 hours.

"There is no way you can escape the fact that volcanoes are releasing a tiny amount of emissions right now," said Bernard Marty of the Centre de Recherches Petrographiques et Geochimiques in Nancy, France. "There is no doubt about this."

"Even if you do the reverse and you compute how much volcanism should happen to match atmospheric levels, you end up with completely unrealistic eruption rates," he said.

Marie Edmonds, a volcanologist at Cambridge University agreed. While volcanoes are the most important natural source of atmospheric CO2, she noted, "The results show clearly that the amount is 100-150 times less than anthropogenic amounts."

http://news.discovery.com/earth/volcanoes-co2-people-emissions-climate-110627.html