Green Myth-Busting: CO2 Emissions
Carbon Dioxide Molecule
Myth: Compared to natural carbon dioxide emissions, manmade emissions are insignificant.
Fact: The argument is occasionally made by global warming skeptics that manmade carbon dioxide emissions are much smaller than natural emissions. Some skeptics will even quote figures in decimal or percent form, which makes it look even more true. If this is the case, according to their logic, our attempts to stop global warming are futile because we can't make a difference. This argument is blatantly false and is based on a complete lack of understanding of our environment.
On our planet, there is an ongoing process called the carbon cycle, in which carbon dioxide is both emitted and absorbed naturally. The absorption part of the cycle is what is missing from this myth. It is true that very large amounts of CO2 are emitted naturally, but there is also a carbon dioxide sink, which is the name for the absorption process. The sink removes slightly more carbon dioxide from the air than is emitted naturally. Therefore, any natural CO2 emissions are a wash.
Carbon Cycle
Actually, the natural sink is also absorbing much of the emissions resulting from human activity. In fact, the only reason any of our emissions end up in the atmosphere is because we're emitting CO2 faster than the planet can absorb it:
The roughly 500 billion metric tons of carbon we have produced is enough to have raised the atmospheric concentration of CO2 to nearly 500 ppm. The concentrations have not reached that level because the ocean and the terrestrial biosphere have the capacity to absorb some of the CO2 we produce. However, it is the fact that we produce CO2 faster than the ocean and biosphere can absorb it that explains the observed increase. - RealClimate
This has resulted in an increase in CO2 concentrations over the last century and a half of about 100 parts per million, from 280 ppm to 380 ppm. Nearly all of this increase has been due to human activity. Another way we know this, besides a simple look at the increase in human activity over the past two centuries, is by measurements of different isotopes of the carbon atom:
Isotopes are simply different atoms with the same chemical behavior (isotope means “same type”) but with different masses. Carbon is composed of three different isotopes, 14C, 13C and 12C. 12C is the most common. 13C is about 1% of the total. 14C accounts for only about 1 in 1 trillion carbon atoms. CO2 produced from burning fossil fuels or burning forests has quite a different isotopic composition from CO2 in the atmosphere. This is because plants have a preference for the lighter isotopes (12C vs. 13C); thus they have lower 13C/12C ratios. Since fossil fuels are ultimately derived from ancient plants, plants and fossil fuels all have roughly the same 13C/12C ratio – about 2% lower than that of the atmosphere. As CO2 from these materials is released into, and mixes with, the atmosphere, the average 13C/12C ratio of the atmosphere decreases. - RealClimate
So, not only are manmade CO2 emissions significant, they actually make up an overwhelming majority of the recent increase in CO2 concentrations in the atmosphere. Looking into the future, manmade CO2 emissions are predicted to continue increasing, which will no doubt result in higher concentrations of the gas in the atmosphere. Therefore, our efforts to cut back on emissions will indeed make a difference for the future of our planet.
Tags: anthropogenic, carbon dioxide, Climate Change, CO2, emissions, Green Myth-Busting, Science and Tech
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July 11th, 2007 at 4:32 pm
Some of the graphs here http://tinyurl.com/2hh9rz might be useful in driving your point home.
Nice post. I really love the carbon cyclic drawing you used. Where’d you find it?
July 11th, 2007 at 4:39 pm
Simply defined:
Matter can change form, but it cannot be created nor destroyed.
In high school chemistry (for those that paid any attention), we learned that chemical equations balance. The numbers and types of atoms in the reactant chemicals must equal the numbers and types of atoms in the solution. All things that burn are hydrocarbons, meaning that they contain hydrogen and carbon atoms. The numbers and types of atoms vary from fuel-to-fuel (i.e. coal, oil, natural gas, gasoline, ethanol, etc.), but they are all still hydrocarbons. Hydrocarbons require an ignition source and only burn in the presence of oxygen, which generally comes from air. Air is a mixture of Nitrogen (78.09%), Oxygen (20.95%), Argon (0.933%), Carbon Dioxide (0.09%), and other trace components. Note how little of the air is CO2 versus how much we worry about its effects on our climate. Anyway, when a fuel burns, CO2 is released as the carbon in the hydrocarbon combines with the atmospheric oxygen. Other by-products are also formed, but let’s limit the discussion to CO2. A simple mass balance will show that the amount of C and O2 that went into the combustion chamber equal the amount of C, O2 and CO2 that exit it. There is no elemental increase, only a change in form.
Again noting how little CO2 exists naturally in the atmosphere, it stands to reason that the marriage is a bit unstable and that CO2 wants to divorce. Why? Why else, so it can get a new partner! O2 likes to combine with hydrogen to make stable H2O, or to remain unattached as free-wheeling O2 participating in less than stable relationships with a host of other elements. C also has desires that are stronger than its bond to O2, so it doesn’t mind the infidelity either. Ergo, the Carbon Cycle is born and declared self-sustaining. Self-sustaining, unless of course, mankind finds some way to exceed the capacity of nature’s carbon sink. We are so diabolical.
But where am I going with all this? The Law of Conservation of Matter and the Carbon Cycle share the flawed assumption that the earth is a closed system. Both theories assume that the available matter in the system is fixed. That’s not necessarily true as the planet journeys through space, because it discharges some matter into space and gets impacted by other matter that exists in space. Does the exchange of terrestrial and extra-terrestrial matter have any effect on climate? Who knows? It appears to be a question that is either being overlooked or explained away; much like we’ve discounted the effects of our nearest star. It may prove out that the mechanics involved in climatology have more variables than we are currently considering; or than we are willing to consider.
July 11th, 2007 at 8:05 pm
Trinifar,
Thanks. I got the picture from Wikipedia (Carbon Cycle).
July 12th, 2007 at 7:44 am
I thought it looked familiar, and if I had read your previous post and its comments I’d have known where you were coming from! Anyway, now registered as a member here and will eagerly await future posts. We need more information written in a style like your that easy to understand.
July 17th, 2007 at 2:46 pm
“The sink removes slightly more carbon dioxide from the air than is emitted naturally” - logically, before the industrial revolution, the CO2 levels in the atmosphere was continuously decreasing - or not?, and as such, somewhere in the past it was as high, or even higher than today - or not?
Additionally, I see no link between all the discussion about isotopes and the conclusion: “..manmade CO2 emissions…make up an overwhelming majority of the recent increase..” , but maybe I am trying to make too much questions, instead of being the true believer.
By the way, 380 ppm makes 0,038% instead of 0.09% described by Bobby B., so it’s more then 2 times lower - only a detail…
November 7th, 2007 at 2:27 pm
At first glance, Jason Leggett’s article proving a primarily anthropogenic cause for the increase in atmospheric CO2 over the past 150 years appears to make sense.
The article states: “Nearly all of this increase has been due to human activity. Another way we know this, besides a simple look at the increase in human activity over the past two centuries, is by measurements of different isotopes of the carbon atom” and “Carbon is composed of three different isotopes, 14C, 13C and 12C. 12C is the most common. 13C is about 1% of the total. 14C accounts for only about 1 in 1 trillion carbon atoms. CO2 produced from burning fossil fuels or burning forests has quite a different isotopic composition from CO2 in the atmosphere. This is because plants have a preference for the lighter isotopes (12C vs. 13C); thus they have lower 13C/12C ratios. Since fossil fuels are ultimately derived from ancient plants, plants and fossil fuels all have roughly the same 13C/12C ratio – about 2% lower than that of the atmosphere. As CO2 from these materials is released into, and mixes with, the atmosphere, the average 13C/12C ratio of the atmosphere decreases.”
The hypothesis is that increases in atmospheric CO2 are “proven” to be anthropogenic in origin because of a reduction in the C13/C12 ratio in the atmosphere.
A closer check of the facts shows that this reduction proves nothing at all.
Fossil fuels and plants have the same C13/C12 ratio, so that CO2 coming from burning fossil fuels will have the same C13/C12 ratio as the CO2 coming from man-made forest clearing, natural forest fires or natural plant decay.
Animal respiration also has the same ratio, since the carbon contained in the exhaled CO2 originally came via digested plant matter (either directly, in the case of vegetarians, or indirectly, in the case of carnivores eating the meat of vegetarians).
There are around 750 billion tons carbon (gigatons or GtC) in the Earth’s atmosphere (primarily as CO2) today, compared with over 50 times as much, or around 41,000 GtC in the “carbon sink” of the world’s oceans (as carbonates, carbonate deposits and marine life). Another 610 GtC are estimated to be contained in the earth’s vegetation, 1,580 GtC in soils and 1,500 GtC in worldwide reserves of fossil fuels.
Annually photosynthesis (from plants, algae, plankton) accounts for a net reduction of slightly over 62 GtC from the atmosphere, while animal respiration plus plant decay account for a slightly smaller increase of carbon into the atmosphere, or 60 GtC.
According to the Hadley Centre, fossil fuel burning plus cement production accounts for 5.5 GtC/year, while “land use changes” (the other “influence of man”) brings another 1.6 GtC/year increase to the atmosphere.
http://www.metoffice.gov.uk/research/hadleycentre/models/carbon_cycle/intro_global.html
Interestingly, at today’s world population of 6.6 billion, human respiration alone accounts for another 0.4 GtC/year, or around 6% of this.
On the assumption that the only way that plant-based carbon can get into the atmosphere is by people burning fuels or clearing forests, Jason Leggett’s article postulates that decreases of C13 in the atmosphere prove that human combustions are clearly identifiable as the primary contributors to the 100 ppm increase in CO2 since 1850.
However, plant decay and animal respiration, which have the same C13/C12 ratio as the 8.6 GtC/year carbon release to the atmosphere from human causes, account together for around 62 GtC/year carbon release to the atmosphere, or around 7 times as much as the carbon resulting from humans.
So it is illogical to assume that a decrease in the C13/C12 ratio is a result of anthropogenic CO2 emissions alone and that this can therefore be used to “prove” that these are caused by man, since the naturally occurring release of C13-deficient carbon is far greater than that caused by people burning fuel.
The hypothesis is also flawed because only around 3 percent of the plant-based carbon on earth is bound up in fossil fuel. The rest of the huge remaining tonnages of plant-based carbon are diffused through the oceans, the forests, the grasslands and the soil.
An estimated 90 GtC are released and 92 GtC reabsorbed annually by the oceans. Cold ocean waters absorb lightweight C12 preferentially, resulting in large quantities of C13-deficient carbon in the oceans. This low-C13 carbon has most certainly been released massively into the atmosphere over the course of the world’s warming trend since 1850, when the Little Ice Age ended and CO2 degassing of the oceans began.
These larger natural pathways for emitting low-C13 carbon into the atmosphere have nothing to do with anthropogenic CO2 emissions burning from fossil fuels.
Conclusion: There is no sound scientific basis for the claim that changes in the isotope ratio of atmospheric CO2 “prove” that the increase in atmospheric CO2 is anthropogenic.
Max
December 29th, 2007 at 5:03 am
[...] Dad is a Geologist and a very, very smart man. He’s written books for his field that I could never even begin to comprehend. And yet, he refuses to agree that man is mainly to blame for the current global warming problem, theorizing that the problem probably has more to do with nature’s own carbon emissions (volcanic erruptions, etc.). Needless to say I was pretty stunned hearing this from him, and found myself stammering to come up with a good rebuttle to his statements. Tonight, while surfing the web for ideas for an upcoming project, I stumbled across this website, which explains that the earth is naturally equipped to filter large amounts of carbon emissions - but unfortunately humans are producing it at a faster rate than the earth is equipped to deal with. Thus, the problem we are now finding ourselves in. For more information, CLICK HERE. [...]
December 29th, 2007 at 5:11 am
Max:
Did you happen to read the very last sentece of the very web page entry you quoted and provided a link to?
“The additional carbon resulting from human activity is the cause of atmospheric carbon dioxide rises over the last 150 years.”
April 11th, 2008 at 5:57 am
Huh… Your blog is nice in general, but this very post… It is brilliant!!! It can be never better.
June 30th, 2008 at 8:54 pm
I recently read a very interesting book by Nigel Lawson called “An appeal to reason”. It contains some very interesting and compelling information regarding the alleged climate change situation. Also if I may say it does seem very irritating, to me in any case, when protagonists of either side of the global climate change dispute insist on obnoxiously asserting what they believe to be “Fact:” To me a much more neutral discussion might seem far more compelling. Indeed I expect that kind of assertiveness from the creationists; full fo zeal as they are.