Volcanoes and CO2

Thar she blows. Eyjafjallajokull erupts in a feast of atmospheric pollution which puts the coal industry to shame. Or does it?

The world we live in has a volcanic history. The continents ultimately came from volcanoes, often volcanic arcs, in some cases several billions of years ago, in other cases more recently. All ocean floor is volcanic, made in mid-oceanic rifts within the past few hundred million years. And the volcanic contributions do not stop there. The air we breath is in part of volcanic origin, and in the absence of volcanoes, would quickly become unlivable. In the list of acknowledgements at the end of the movie ‘The human race’ (coming soon to a planet near you), volcanoes will feature prominently, immediately after the main actors, and in a big font; perhaps they will also feature in the funny outtakes at the end, for instance the Yellowstone eruption which was accidentally filmed supersized, wiping out all of human life and requiring a re-take, however I expect that human bloopers will provide a plethora of choice already, enough to fill up an entire youtube channel. (Thinking about it, isn’t human bloopers what most television channels already show?) We are volcanoes’ living heritage.

But not everything volcanoes do is to our benefit. The lava flows build new land but also burn down what was before. The gases that are emitted range from harmless (water) to dangerous (SO2, HF) and deadly (CO). But one of those volcanic gases has everything. CO2, which accounts for 10 per cent of the gas emitted by volcanoes, is the killer we could not live without. It keeps our Earth warm but in excess causes global heating. Is it for better or for worse? And is it true, as some have claimed, that volcanoes emit more CO2  than humans do? Ian Plimer famously stated “Over the past 250 years, humans have added just one part of CO2 in 10,000 to the atmosphere. One volcanic cough can do this in a day.” A politician, Mike Huckabee, said “The volcano that erupted over in Northern Europe actually poured more CO2 into the air in that single act of nature than all of humans have in something like the past 100 years.“ He can be forgiven for not trying the pronounce the name Eyjafjallajökull. But what is the scientific truth? How much do volcanoes contribute?

Before we continue, you may want to take a quick test, comparing human and volcanic emission per year.

And one more polling question about comparing volcanoes to humans:

The miracle of carbon

So why is carbon so important? After all, the amount of CO2 in the Earth’s atmosphere is minuscule. But carbon does much more than making CO2. The biosphere is a carbon world. Life requires organic chemistry, and organic chemistry demands carbon. It is a versatile atom which can make four bonds with other atoms. This opens up a world of possibilities. It can bond (boringly) with four hydrogens, to make methane. It can do two oxygens instead (each oxygen accounts for two bonds), making the life-giving killer CO2. Or it can mix and match bonds, say H2CO or OCS. Putting a hydrogen on the oxygen, so that only one bond is needed to weld the OH to the carbon leaves three bonds free, and allows H3COH – methanol. The real power comes, though, from carbon bonding with carbon. Immediately, H3CCH2OH becomes possible, that essential molecule for (previously) intelligent life, ethanol (alcohol). Include nitrogen, and you enter the realm of the complex molecules that define life, from the busy-bees of the amino acids to the digital information systems of DNA. The only atom that can compete in complexity is silicon, which can also do four bonds. Whilst carbon makes an unending series of different molecules, silicon instead makes crystals, equally wonderful and complex but inert. Theirs is the elegance of autism, a wonderful world, greatly rewarding the effort needed to understand its beauty. But to build an organic world, you need to interact in ways that silicon, frozen in place, just doesn’t. Carbon is the wonder that carries the gift of life.

Glycine, a simple amino acid

It also carries the gift of death. The complexity of carbon molecules makes their chemistry unpredictable. One misplaced reaction can destabilize the intricate web upon which life depends. Even a molecule as simple as benzene is dangerous. The art of making pesticides is finding a molecule that kills one thing but is harmless to everything else – a dangerous dream which requires a great deal of wishful thinking. Life came out of complexity, and complexity brings with it fragility. But that is a different story. And even a molecule as simple as CO2 is a mixed blessing. Plants can’t live without it; animals can’t live with it. A few per cent of CO2 in the air stops our blood from carrying oxygen, with deadly consequences. It is used to carbonate our drinks, adding excitement to bland liquid sugar, but it is best to avoid breathing the liberated gas. Even the machines that make carbonated drinks are known to have caused fatalities.

Degassing in Lake Nyos: a pipe runs to the bottom, and the CO2 from the saturated bottom layers pushes up through it. The overpressure causes a large fountain. In some ways, it behaves as an artificial volcano. Three such pipes have now been installed in the lake, and they should prevent a re-occurrence of the 1986 disaster. The pumps run entirely on the energy released by the gas pressure – adding CO2 to the atmosphere in the greenest way possible. https://globalchange.umich.edu/globalchange1/current/lectures/kling/killer_lakes/killer_lakes.html

Volcanoes are also implicated in CO2 fatalities. In February 1979, following a phreatic eruption, Dieng volcano, in Indonesia, released nearly pure CO2 gas. 142 people died in the valley below the volcano, from asphyxiation. (Such a CO2 discharge from a vent is called a mofetta.) Cameroon has also fallen victim. It contains two volcanic lakes, which capture CO2 emitted by hydrothermal springs at the bottom of the lake. These two lakes lack a regular turn-over of the water: the bottom water stays where it is, aided by the fact that adding CO2 makes water heavier. The lakes have become strongly stratified and the bottom layers eventually become saturated with the gas. Until, at some point, this stratification fails. The water at the top suddenly sinks down, the bottom water comes to the surface. the CO2 suddenly –and explosively- comes out of the solution (think a coke bottle shaken, not stirred), and is released into the atmosphere. On 21 August 1986, this happened at Lake Nyos: 1700 people died. The gas burst caused a 25-meter high lake tsunami, but the real killer was the gas. There had been an earlier warning: nearby Lake Monoun had done the same thing in August of 1984, killing 37 people. Why did it happen twice in August? August is the monsoon season, when the rains cool the surface. Cooler water is denser, and this time it became denser than the CO2-rich bottom water. Still waters can hide fizzy killers. Lake Nyos is now under control, but there may be other such ticking time bombs in Africa.

CO2 suffers from more bad press. It is implicated in the acidification of the oceans, and in the inexorable rise of worldwide temperatures. The latter is a complete accident of physics. CO2 happens to absorb radiation that would otherwise carry heat from Earth to space. The Earth acts like a room where the radiator is always on, and the temperature is regulated by opening and closing curtains. CO2 is that curtain, and as more is added to the atmosphere, the curtain becomes thicker. We are now implementing carbon budgets, and countries are slowly becoming committed to limit their emissions to amounts the Earth can cope with. But as Lake Nyos demonstrated, not all CO2 is humane. Are volcanoes in compliance with the Paris agreement? Or are we kidding ourselves by regulating our own emissions whilst ignoring the unstoppable volcanoes?

Carbon accounting

Let’s put some numbers into this discussion. The current concentration of CO2 in the atmosphere is around 400 ppm. ‘ppm’ stands for ‘parts per million’. A number of 400 means that out of every 10,000 molecules in the air (where water molecules are excluded from the count), CO2 accounts for 4. In comparison, over 2000 of those molecules are O2, and 100 are argon. If you were to buy the essential ingredients needed to make air, CO2 wouldn’t feature on the shopping list.

CO2 emissions are measured in weight rather than number of molecules. Take a square meter of ground: the air column above it contains 6.1 kilogram of CO2. To get the total amount of CO2 in the atmosphere, multiply this number by the total surface area of the Earth. It comes to 3.1 x1015 kilogram of CO2 – or 3130 gigatons, if you prefer.

To confuse things further, sometimes the total weight of carbon is quoted rather than that of CO2. The ‘C’ accounts for 32 per cent of the weight of CO2 (the rest is in the two oxygen atoms). So the total amount of carbon in the atmosphere at the present time is 996 gigatons. Adding methane (2 ppm) brings this up to almost exactly 1000 gigatons of carbon.

NASA’s view of CO2 in the air

Carbon in the biosphere

Measuring the weight of carbon rather than CO2 is useful in cases where carbon is in a different form, for instance organic molecules. This is the case in the biosphere: the sum of all living things. Let’s start with ourselves. The human body is about 18 per cent carbon by weight. If we take our average weight as 60 kg, and a current number of 7.5 billion people, humanity accounts for 83 million tons of carbon. (The CO2 equivalent would be 3.1 times larger, i.e. 250 million tons.) Domesticated animals account for perhaps twice as much as people. Wild land animals contain a sum total of 5 million tons of carbon. An interesting aside is that, since the population explosion, humanity outweighs all wild land animals combined by a factor of 15! This may give a whole new reason why, wherever people spread, large animals went extinct. We took their carbon.

But animals are a minor contribution to life. Plants account for 550 gigatons of carbon: they outweigh us by a factor of 6000! The contributions from all other types of life are quite uncertain: some papers claim that bacteria dominate everything, others dispute this. Recent research seems to favour lower numbers for the total bacterial weight, mainly because much of the oceans seem to be too nutrient-poor to support large communities.

The total amount of carbon in the biosphere is estimated at about 1000 gigatons . But the uncertainties are such that it could be twice as high or a bit less. The equivalent is 3100 gigatons of CO2. This is about the same amount as there is in the atmosphere, a curious coincidence.

As an aside, the numbers show that the majority of the carbon mass of the biosphere is on land! This is because plant life dominates, and there are very few plants in the sea. When plants colonized land, biomass exploded. The sea has much more living space than the continents do, but much of it is poor in nutrients. It may not be an accident that the Cambrian explosion coincided with the origin of land plants. They expanded the biosphere, and the sea benefited through run-off of the detritus leading to an algae bloom. To farm the sea, find fertilizer.

Non-biological carbon

But life is not everything. There is also a lot of non-biological carbon in the sea: around 37.5 thousand gigatons. And around 2700 gigatons of carbon is hiding in the soil. To put this in context, remember that there is 1000 gigatons of carbon in the air (as CO2) and a similar amount in life. If we convert it to equivalent CO2 mass, the ocean, soil, air and life contain 116, 8.4, 3.1, and 3.1 thousand gigatons.

The carbon in the sea, soil, air and life (plants, mainly) is roughly in ratio 37:3:1:1. The large majority of carbon is non-biological, dissolved in sea water. Life makes quite efficient use of the carbon available to it in the air and soil (it has taken up about 20 per cent), but the huge pool of carbon in the oceans has remained largely inaccessible. The oceans are not friendly to life.

Part 2 of this post gives the detailed accounting of volcanic and humanic emissions, including identifying the most polluting volcanoes! And the answers to the poll questions.

29 thoughts on “Volcanoes and CO2

  1. Thank you Albert! A very detailed and fascinating article! I wish I had the skill to pull together information and present it like you.

  2. I look forward to future parts – a very perceptive review article. I have a couple of questions. (1) Am I correct in reading into it, that the total amount of animal biomass and contribution to atmospheric CO2 has not, as far as we can tell, been affected by the human population explosion because it has been offset by a decline in other animal populations. (2) It seems to me that in geologic time there is an automatic correction, as higher CO2 and warmer temperatures both increase photosynthesis and this leads to sequestration of carbon.

    • I don’t think we know how animal biomass has changed over time! At least, I could not find any studies and had to do the numbers myself. Gras land supports massive numbers of large animals, and these huge herds have disappeared because of us. I would guess that we do have more biomass than they had but not by a large fraction – however, I have no data to back up this feeling. The automatic correction is not automatic. Higher temperatures (beyond our current ones) lead to less plant matter, unless you also increase rainfall: this is because at higher temperatures, plants require more water. In some high-CO2 epochs in the past, much of the land was desert. But at other times there was very productive forests, namely the ones that formed our coal deposits. Be aware that forests are good at locking away carbon, but poor at supporting animal life. You couldn’t have our human society with food production dependent on forests – we’d starve.

      • Actually the important figure is not animal biomass but animal metabolism. A kilo of mice emits more CO2 per unit of time than a kilo of elephants. As a mycologist by training I feel the decomposers are given short shrift in your analysis; decomposition is another source of atmospheric CO2. There’s no evidence of dramatic shifts in decomposer balance in the Quaternary let alone human history, but there is some evidence at the Permian Triassic boundary.

      • Albert, that was a very excellent and insightful article. It really sets out the scale of things, something that is almost always lacking.
        The human biomass relationship is also quite extraordinary and shows very clearly why we need to drastically cut population for both our own and the rest of the planet’s good. Without industrial farming worldwide the sustainable world population is probably well under 1B and industrial farming is unsupportable long term for world populations much bigger than we have. Eventually populations will fall, by design or famine of epic proportions.
        To note that UK wheat yields in the early 1970’s were typically about 4T/Ha ((and probably had been for millennia) and the other year we *averaged* a record 12.8T.Ha. The reason for this is a cocktail of all of the following:

        Excellent weed control: so wheat is now 500mm high and not 2m, and the straw biomass is now grains (probably worth 4T/Ha).
        Excellent fungicides: Prevents crop damage and loss and diversion of biomass to plant antifungal mechanisms. Variable, typically 30%, range 5-100%.
        Fertilisers: allows full yield potential to be achieved. Nitrogen in particular is limiting in nearly all situations. Typically some 6-8T/ha,
        Moisture stress: Wheat is rather drought resistant, other plants less so.
        Sunlight: One of the reasons for the record yields was high sunlight levels and cool weather. For the UK this is now a major indicator of potential yield.

        Note that these are not additive, if any one fails they all fail and also that I have not mentioned soils. More rubbish is talked about soil than anything else, its important but really not a problem to manage if you know what you are doing. The main soil effect is moisture retention, which is pretty physical and note that (for wheat) its the top 2M that counts, far below the topsoil.

        I think this era will end with massive famine, probably with war as a starter. probably now inevitable. Sad, but there you go.

        • High human population levels are clearly dependent on artificially high and unsustainable plant productivity. There are vulnerabilities to pests and pathogens which are comparable to vulnerabilities in human and domestic animal populations due to over-reliance on antibiotics. Major crops like wheat and maize are genetically very uniform, and we have lost the genetic history from which resistance to a novel or emergent pathogen might derive. There are also documented cases of naturally occurring but relatively harmless parasites which produce cross immunity to dangerous pathogens; monoculture and heavy use of pesticides and fungicides circumvents this natural source of immunity.

          • Its not really very true that current farm productivity is unattainable under the existing world political and economic situation, however falling energy availability and rising population levels means that this proviso looks to be unrealistic.

            Its simply not true that plant breeders cannot keep ahead of pathogens, certainly if modern methods of genetic manipulation are used. Much of the slowdown in products for weed and pest control are due to very high costs of registration of new products which mean that manufacturers are increasingly not bothering to find any.

            Fertiliser supplies are pretty well unlimited, certainty in the medium (centuries) term.

        • I am amazed how much productivity has gone up. Agriculture has been a success story. But it is harder to see where the next step up is going to come from, which will be needed with another 30% increase in human population likely. The vulnerabilities in the system are scary. A major crop disease seems a matter of time: do we still have a backup strategy? The critical test may come from the farmland in China, which needs to feed a lot of people in an increasingly problematic environment.

          • There are huge areas of the world where agriculture has not fully been developed particularly in south America and Africa. Sadly this has rather large and irreversible ecological costs, but the local population will probably do it just the same, and who are we in the northern hemisphere to complain when we did just the same thing. So yes, another 30% is technically readily doable.

  3. Disappointing to see that 60% of the poll thinks volcanoes emit more than humans. We don’t have too many climate sceptics I hope!

    • It’s arguable that the question is confusing. Volcanoes have been around a lot longer than we are (although the god-botherer fraction of the climate change deniers might dispute that.

  4. True. Once a poll has been set up, it can’t be changed, I think (for good reason). But I guess people will understand what the question means.

  5. The new Sentinel world maps are nice. A cloudless world map has been made which is fun to zoom around in. The Sentinels do not give the resolution of Landsat, but they are fine for volcanic features. I did find a few clouds which had survived the culling. No labeling or search facility: you have to know your geography! And the projection is not ideal at higher latitudes. But still a useful tool: see https://s2maps.eu

    • Hi Albert, thanks for linking to our maps. Actually the resolution of Sentinel-2 is just a little better than Landsat-8 (10m vs. 15m). Yes, we have to admit that some clouds are still visible. We suppose they are mostly there because of fewer data available (see details in a recent presentation https://git.osgeo.org/gogs/foss4g-europe/foss4g-europe-2017-paris/src/master/presentations/2017-07-19/general_track/foss4g-europe-2017-A_cloudfree_Europe_with_sentinel2-JUngar-SMeissl.pdf). If you need labels there is a button to enable them at the top left when exploring the map. The projection is simple LongLat or EPSG:4326 which looks a little distorted to usually known maps but allows to show data above 85° north. Btw. we also serve Google Mercator (EPSG:3857) tiles from our WMTS endpoint.

      • Thanks Stephan! It is a very nice resource. I noticed a few clouds on Hawaii, for instance, in areas where probably the majority of observations had cloud cover – it rains a lot. My home town, Manchester, is cloud-free which is quite an achievement. Thanks for pointing out the label button – I had missed it.

  6. So far, the polls show disagreement about whether volcanoes or people dominate CO2 emissions: both have almost exactly the same number of votes. There is a strong majority for volcanoes outperforming our breathing, in CO2 production. Keep voting! The next instalment of the post is scheduled for tomorrow, when the answers will be revealed!

  7. If volcanos would emit more than humans then this should be visible on the co2 graphs.

    Held for approval by the filter. hereby released – admin

  8. If you are going to discuss CO2 concerntration then you need to discuss Henry’s Law. The partial pressure difference between gas phase and liquid phase is controlled by the temperature of the liquid. Ie the ratio between the ocean and atmosphere is 37:1. When you release CO2 into that atmosphere only 1/37th will remain in that atmosphere at equilibrium. Current estimates from IPCC put the turnover at approximately 10% per year. If the temperature of the ocean warms then it degasses to the atmosphere. Also if the ocean cools you get the reverse. A good example of this occurred 20 million years ago when the Antarctic split from australia and formed a circumpolar ocean that allowed deep cold water to form and subsequently reduced the global CO2 from 800ppm to 400ppm. It should be noted that the C3 photosynthesis pathway is inhibited below 800 ppm as plants evolved at much higher concentrations (10000ppm during Carboniferous period when much coal was laid down) It should also be noted that below 200ppm photosynthesis stops and all life dependentant on it dies.
    As for global warming, we are in an Ice age still, a state that present for just 20% of the time multicellular life has been around. There used to be polar forest where dinosaurs roamed. We are still 2deg Cooler than the Holocene optimum. The climate has always been variable! Adapt or die.

    • Henry’s law is irrelevant in this case. The mixing between ocean and atmosphere is very slow, so it takes thousands of years for equilibrium to be reached. Only the surface layer can exchange gas, and the ocean has a lot of volume for its surface area. And once in the water, CO2 reacts to form other compounds, so overall it is a far more complex system than you imagine.,

      The last time global temperatures were at current level, sea level was 7 meter higher than it is now (and your number is wrong: we are already higher than the previous holocene peak). I wish you well in your adaptations. Let me know how you get along. And in case you can manage: last time CO2 levels were at current levels, sea level was something like 20 meter higher. Just something to keep in mind.

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