# Volcanos, Humans and Global Warming **URL:** \ **Category:** Factual Questions\ **Created:** [April 25, 2001, 7:23pm UTC](https://boards.straightdope.com/t/volcanos-humans-and-global-warming/63332 "2001-04-25T19:23:12Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![shelbo](https://avatars.discourse-cdn.com/v4/letter/s/3d9bf3/32.png) [@shelbo](https://boards.straightdope.com/u/shelbo)\ **Post date:** [April 25, 2001, 7:23pm UTC](https://boards.straightdope.com/t/volcanos-humans-and-global-warming/63332/1 "2001-04-25T19:23:12Z")
Here’s a statement recently made in an argument over Global Warming, CO2 emissions, etc. "Given the fact that ONE volcano erruption can spit out more CFCs and green house gasses than man ever has, the only logical conclusion is that WE DON’T HAVE A CLUE as to whether man’s activities have had any effect whatsoever on the the earth’s mean temperature. " [sic] Here’s a statement made by Ace Face on one of the GD Threads re: Global Warming. “The current best estimate is that all volcanoes combined produce about 110 million tons of carbon dioxide a year, while humans produce about 10 **billion** tons per year. The other major greenhouse gas contributed by volcanoes is sulfur dioxide, which is converted to sulfuric acid aresols, which have a cooling effect.” Does anyone have any facts supporting one view or the other? ---
**Author:** ![Terminus\_Est](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/terminus_est/32/3087_2.png) [@Terminus\_Est](https://boards.straightdope.com/u/Terminus_Est)\ **Post date:** [April 26, 2001, 1:50am UTC](https://boards.straightdope.com/t/volcanos-humans-and-global-warming/63332/2 "2001-04-26T01:50:01Z")
Volcanos do indeed produce carbon dioxide and sulfur dioxide, both greenhouse gases. A volcanic eruption spews a lot of gases in a relatvely short period of time, while man-made emissions are continuous year after year. [Gases: Man versus the Volcanoes](http://volcano.und.nodak.edu/vwdocs/Gases/man.html) > [@](#): > > Do we add more gases to the atmosphere or do volcanoes? It’s a simple question with a complicated answer. Reaching a good estimate is important in guiding global policy for standards to reduce emissions from man-made sources of gases. > > Carbon Dioxide > > Present-day carbon dioxide (CO2) emissions from subaerial and submarine volcanoes are uncertain at the present time. Gerlach (1991) estimated a total global release of 3-4 x 10E12 mol/yr from volcanoes. This is a conservative estimate. **Man-made (anthropogenic) CO2 emissions overwhelm this estimate by at least 150 times.** > > Sulfur Emissions > > […] > > Volcanoes and other natural processes release approximately 24 Tg of sulfur to the atmosphere each year. Thus, volcanoes are responsible for 43% of the total natural S flux each year. Man’s activities add about 79 Tg sulfur to the atmosphere each year. **In an average year, volcanoes release only 13% of the sulfur added to the atmosphere compared to anthropogenic sources.** Note that while carbon dioxide has a warming effect, sulfur dioxide has the opposite effect. [Climate: Cooling](http://volcano.und.nodak.edu/vwdocs/Gases/climate.html) > [@](#): > > Symonds, Rose, Bluth, and Gerlach concluded that stratospheric injection of sulfur dioxide (SO2) is the principal atmospheric and global impact of volcanic eruptions. > > SO2 + OH + 3H2O -\> H2SO4 (l) + HO2 > > The SO2 converts to sulfuric acid aerosols that block incoming solar radiation and contribute to ozone destrucion. The blocked solar radiation can cause global cooling. > > The amount of SO2 released by volcanoes is much less compared to man-made sources but the impact of some eruptions might be disproportionately large. The gases emitted by most eruptions and by man-made sources never leave the troposphere, the layer in the atmosphere from the surface to about 10 km. Volcanic gases reach the stratosphere, a layer in the atmosphere from about 10 km to about 50 km in altitude, during large eruptions. This relationship is complicated by the fact that the elevation between the volcano summit and the distance to the troposphere/stratosphere decreases with latitude. So, some smaller eruptions at higher latitudes can eject as much SO2 gas into the stratosphere as larger eruptions closer to the equator. I doubt that volcanos spew out chloroflurocarbons (CFCs), since these wholly man-made. Regardless, CFCs don’t contribute to global warming - they break down ozone and are implicated in the development of the ozone hole over Antarctica. Volcanic impact, if any, on the ozone layer is due to emission of HCl. [Volcanoes and Ozone](http://volcano.und.nodak.edu/vwdocs/Gases/ozone.html) > [@](#): > > Volcanoes account for about 3% of chlorine in the stratosphere. Methyl chloride produces about 15% of the chlorine entering the stratosphere. The remaining 82% of stratospheric chlorine comes from man-made sources, mostly in the form of chlorofluorocarbons. > > Although volcanic gases do not play a direct role in destroying ozone they may play a harmful indirect role. Scientists have found that particles, or aerosols, produced by major volcanic eruptions accelerate ozone destruction. The particles themselves do not directly destroy ozone but they do provide a surface upon which chemical reactions can take place. This enhances chlorine-driven ozone depletion. Fortunately, the effects from volcanoes are short lived and after two or three years, the volcanic particles settle out of the atmosphere. Poke around in [Volcano World](http://volcano.und.nodak.edu/vw.html) for more information. ---
**Author:** ![wevets](https://avatars.discourse-cdn.com/v4/letter/w/e9a140/32.png) [@wevets](https://boards.straightdope.com/u/wevets)\ **Post date:** [April 26, 2001, 2:05am UTC](https://boards.straightdope.com/t/volcanos-humans-and-global-warming/63332/3 "2001-04-26T02:05:32Z")
According to the [CIA](http://www.cia.gov/cia/publications/hies97/k/tab132.htm), emissions of CO[sub]2[/sub] from many of the major contributors amounted to 4.5 billion metric tons in the year 1994. This can be expressed as 6.2 billion tons of \*carbon equivalent \* (weighing the CO[sub]2[/sub] by its [Global Warming Potential](http://www.epa.gov/globalwarming/emissions/national/gwp.html))according to [this site (mostly focused on Japanese emissions)](http://www.epcc.pref.osaka.jp/apec/eng/earth/global_warming/co2.htm). From [Volcanologist Don Thomas](http://volcano.und.nodak.edu/vwdocs/frequent_questions/top_101/Effects/Effects1.html), volcanoes worldwide produce an average of about 500,000,000,000 kilograms of CO[sub]2[/sub] a year or 0.25 billion metric tons a year. While Dr. Thomas has listed 8.8 billion metric tons as anthropogenic inputs of CO[sub]2[/sub], somewhat different from the numbers I posted above, I think it likely that derives from his using different sources from mine, and perhaps different years, possibly different estimates of _net_ input. It strikes me as likely that the first statement you quoted hinges on the word **can**. How extreme would an eruption have to be to exceed the amount of greenhouse gasses man has _ever_ emitted? It’s also interesting to note that the first person you quoted talks about “greenhouse gasses,” while the second talks about carbon dioxide. ---
**Author:** ![wevets](https://avatars.discourse-cdn.com/v4/letter/w/e9a140/32.png) [@wevets](https://boards.straightdope.com/u/wevets)\ **Post date:** [April 26, 2001, 2:08am UTC](https://boards.straightdope.com/t/volcanos-humans-and-global-warming/63332/4 "2001-04-26T02:08:12Z")
Confound my slow typing fingers! Good work, Terminus Est. 😉 ---
**Author:** ![wevets](https://avatars.discourse-cdn.com/v4/letter/w/e9a140/32.png) [@wevets](https://boards.straightdope.com/u/wevets)\ **Post date:** [April 26, 2001, 2:13am UTC](https://boards.straightdope.com/t/volcanos-humans-and-global-warming/63332/5 "2001-04-26T02:13:35Z")
_slaps self on forehead_ I’m an idiot!! The Japanese site I linked is using different figures than the CIA site. They just happen to be for the same year. Carbon equivalent weights of carbon dioxide are exactly the same as the weight of carbon dioxide. What was I thinking?? ---
**Author:** ![Phobos](https://avatars.discourse-cdn.com/v4/letter/p/3d9bf3/32.png) [@Phobos](https://boards.straightdope.com/u/Phobos)\ **Post date:** [April 26, 2001, 12:59pm UTC](https://boards.straightdope.com/t/volcanos-humans-and-global-warming/63332/6 "2001-04-26T12:59:44Z")
> [@](#): > > \*Originally posted by Terminus Est \* > Regardless, CFCs don’t contribute to global warming - they break down ozone and are implicated in the development of the ozone hole over Antarctica. In Carl Sagan’s “Pale Blue Dot” (sorry, that’s the best reference I have on-hand at the moment), he says that CFCs are a greenhouse gas, but a very minor one. Of course, as you said, the main concern with CFCs is ozone layer depletion. ---
**Author:** ![Una\_Persson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/una_persson/32/346_2.png) [@Una\_Persson](https://boards.straightdope.com/u/Una_Persson)\ **Post date:** [April 26, 2001, 1:49pm UTC](https://boards.straightdope.com/t/volcanos-humans-and-global-warming/63332/7 "2001-04-26T13:49:58Z")
> [@](#): > > \*Originally posted by Phobos \* > \*\*In Carl Sagan’s “Pale Blue Dot” (sorry, that’s the best reference I have on-hand at the moment), he says that CFCs are a greenhouse gas, but a very minor one. Of course, as you said, the main concern with CFCs is ozone layer depletion. \*\* Sagan, IMO, was using the term a bit too liberally. Nearly any gas in the atmosphere is a greenhouse gas to some extent. Note that if we did not have any greenhouse effect at all, this would be a far, far colder planet. And is it too much to ask that Journalists reporting on energy matters get an education and try to at least understand how the World Around Them works? While reading a Time magazine on the flight last night, I noted that they claimed that wind power had already removed the need for “15 coal power plants”. Just that - 15 coal power plants. Oh really? What kind of coal power plants? Did they mean 15 of 20 MW stoker boilers, or did they mean 15 of 1350 MW AEP pulverized coal furnaces? And what is a plant? The terms “unit” and “plant” are used interchangably, both inside and outside the industry. Is a “plant” one unit (such as a single 200 MW unit), or is a “plant” a whole plant site of multiple units (like one of ESKOM’s 10x600 MW plants, for 6000 MW total)? Their definition of “15 coal plants” could mean as little as 300 MW, or as much as the entire generating capacity of the Tennessee Valley Authority. Never mind - just me ranting again.