Our missive of rational thought and balanced opinion, the Avalanche Journal newspaper, today carries on the editiorial page a comment posted by one adunn, that starts off like this:
"More carbon dioxide is put into the atmosphere by a single large volcanic eruption than has been released by the human race since the discovery of fire. And there have been many volcanic eruptions."
True or false? There are three ways to approach this.
1. Authority. The USGS says at http://hvo.wr.usgs.gov/volcanowatch/2007/07_02_15.html, quote:
"[i]Our studies show that globally, volcanoes on land and under the sea release a total of about 200 million tonnes of CO2 annually.
"This seems like a huge amount of CO2, but a visit to the U.S. Department of Energy's Carbon Dioxide Information Analysis Center (CDIAC) website (http://cdiac.ornl.gov/) helps anyone armed with a handheld calculator and a high school chemistry text put the volcanic CO2 tally into perspective. Because while 200 million tonnes of CO2 is large, the global fossil fuel CO2 emissions for 2003 tipped the scales at 26.8 billion tonnes. Thus, not only does volcanic CO2 not dwarf that of human activity, it actually comprises less than 1 percent of that value[/i]." [emphasis added.]
2. Consideration of the Threshhold or Buffering Effect. The earth exerts a buffering effect on changes. For example, as CO2 in the amosphere increases, the oceans sop up a lot, and plants become slightly more efficient at using CO2 to build up plant tissues (which is itself slightly offset by plant respiration, which takes up oxygen and releases CO2). But the oceans are reported as at CO2 saturation, even around antarctica, which is especially important because colder water can absorb more gas (a real killer being that, as ocean temps rise, a lot of CO2 is released as the water warms because warmer water can hold less CO2 in solution! Which has started to happen.)
Ever titrate an unknown acid or base solution in chemistry lab? You've got a beaker of an unknown concentration of acid or base in it, along with a color pH indicator like phenolphthalein, and you add known volumes of an acid or base to neutralize whatever it is in the beaker. You dump some solution in, and nothing happens. Dump some more in, and nothing happens. Let fall a drop more, and voila, instant color change. The earth is like that. Add CO2, nothing happens to atmospheric CO2. Add a little more, nothing happens, because the earth is capable of buffering or neutralizing the CO2 -- up to a point. And then, a little more CO2, and big atmospheric change. Point being that we have reached or are reaching the buffering limit of the earth. A little more CO2, big change. So how much CO2 volcanoes emit is just another nail in the environmental coffin.
What counts is not whether there is a CO2 contribution from volcanoes or not, but whether the earth has been pushed off the precipice yet by that last drop of CO2.
3. Do your own calculations. One big active volcano is in Iceland. According to googled results, it emits as a top figure, 300,000 tons of CO2 per day. That's a lot. And over a year's time there are maybe 50 volcanoes that are active, most emitting less CO2 than 300,000 tons. So just for comparison, how much CO2 do we in Lubbock County, Texas, emit from the burning of petroleum and natural gas and propane and coal?
That's hard, because it requires a lot of data about power plant fuels (some of which are coal and some of which burn natural gas) and propane sales and natural gas sales. Let's make it simpler; take only consumers of gasoline, not commercial drivers, just consumers like you and me.
There are, what?, 240,000 people in Lubbock County? Figure a fourth of us are drivers. 60,000. Figure that we drive an average of 15,000 miles a year. That our average fuel economy is 20 miles per gallon (That's a little high, but let's leave it).
A gallon of gasoline weights a bit more than 6 pounds. Most of that is carbon, because while there are more than twice as many hydrogen atoms as carbon atoms, a carbon atom weighs 12 times as much as one hydrogen atom. When you burn gasoline completely, you get CO2 and water. We are worried about CO2, so forget the water. Forget also that there are traces of sulphur in gasoline, and that the process of combustion at high temp and pressure can create some nitrogen compounds.
When you burn carbon completely, you get CO2. One atom of carbon, atomic weight of 12, combining with two atoms of oxygen which together have a atomic weight of 32, and so the CO2 molecule has a molecular weight of 12+16+16=44. So, 6 lbs of carbon in a gallon of gasoline burns to form 6 X 44/12 = 22 lbs of CO2. Say 20 pounds of CO2 per gallon.
60,000 drivers X (15,000 miles/20 mpg) X 20 lbs = 900,000,000 lbs of CO2 per year. Which is 450,000 non-metric tons per year.
Not as much as a big volcano, which can emit 2/3 that in a day, but Lubbock County is a drop in the bucket of U.S. population and industry. Actually Lubbock County pop is about 1/1300 U.S. pop, so multiplying 450,000 tons by 1300 = 585 million tons for USA non-commercial drivers. Which is a lot more than the CO2 emissions by a single large volcano. Which disproves the assertion in a fun way.
Actually though, Lubbock County probably produces a couple of billion pounds of CO2 yearly from fossil fuels all told. Or more.
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