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Thin Soup and a Thin Story

Filed under: — david @ 2 May 2007 - (Türkçe) (Български)

A firm called is getting a lot of airplay for their bid to create a carbon offset product based on fertilizing the ocean. In certain parts of the ocean, surface waters already contain most of the ingredients for a plankton bloom; all they lack is trace amounts of iron. For each 1 atom of iron added in such a place, phytoplankton take up 50,000 atoms of carbon. What could be better?

Phytoplankton biomass does not last forever, any more than tree biomass does. The trick therefore is to get the carbon to sink out of the surface ocean into the depths, generally in the forms of snot and poop. Once it reaches a depth of a kilometer or so, it can decompose to CO2 again but the water will be isolated from the atmosphere for decades, maybe centuries.

There have been iron fertilization experiments of the ocean before, many of them, in the equatorial Pacific, the Southern Ocean, and the North Pacific. These are places where the ocean chemistry is right for iron fertilization, that is, where there is available nitrogen as nitrate or ammonia, and phosphorus. The experiments uniformly find that phytoplankton growth is stimulated by iron. But most studies have not found an increase in the rate of organic carbon sinking into deeper waters.

If could be, however, that a sustained fertilization will allow the snivelers and the poopers time to get their acts in gear and start exporting carbon more efficiently. This was the conclusion of a recent analysis of natural iron fertilization by the Kerguelen Plateau in the Southern Ocean (Blain et al, 2007). Previous iron fertilization experiments were generally single-pulse additions of iron dissolved in acid. The iron lasted a few days before sinking out on particles or mixing down. If iron were released into the ocean in the form of floating time-dissolving pellets, the steady stream of iron would probably be a more effective fertilizer than the single dumps were.

Once the CO2 concentration of the upper ocean is depleted by growth and sinking of phytoplankton, the timescale for gas exchange with the atmosphere is about a year for a one-hundred meter ocean mixed layer, typical of the tropics. Tropical surface waters, one could argue, will still be at the surface a year from now, so there is plenty of time for them to replenish their CO2 concentration by sucking it out of the atmosphere.

The problem with the tropics is that if tropical surface waters are destined to remain at the surface for a while, they are also probably destined to ultimately scrounge the iron they need, to use the available nitrogen and phosphorus. The water might duck into the thermocline for a few decades, but it will ultimately resurface and be subject again to photosynthetic plankton and iron fertilization from falling dust. Marinov et al (2006) showed that a stimulation of phytoplankton production in one part of the ocean usually acts to depress production elsewhere. So what’s the point of paying for a carbon offset to fertilize a water parcel now, when nature would fertilize it soon anyway? That’s against the rules of offsets; it has to be something that wouldn’t happen anyway.

The one part of the ocean where fertilization of the ocean does not depress the fertility elsewhere is the deep Southern Ocean. Here the water sinks to the abyss, rather than taking a leisurely tour through the upper ocean. But now the practical picture looks different. Instead of the benign tropics, you have sea ice, waters mixed to hundreds of meters down (bad for phytoplankton) and total darkness for much of the year. Fertilize that!

Modelers have long ago concluded that iron fertilization of the ocean can play only a small role in managing the carbon cycle in the coming century. Part of the issue is that the Southern Ocean also covers only a very small area of the surface ocean, just a few percent. Model experiments where the Southern Ocean is completely fertilized show a drawdown of maybe 15 ppm by the year 2100 [Zeebe and Archer, 2005]. We could change a light bulb and do better than that.

Perhaps however the total potential drawdown from ocean sequestration is the wrong question to ask. The total rate of biological export production in the ocean is probably of the order of 15 Gton C / year, and the fertilization enhancement could be at most maybe 1 Gton C / year. That can’t slay the 7 Gton C / year fossil fuel CO2 dragon all by itself, but could it help? Nowadays we’ve given up the idealistic search for a single solution, and we’re building the future out of wedges [Pacala and Socolow, 2004], or what the more dignified IPCC Working Group III calls a “portfolio of solutions”. Would carbon offsets by fertilizing the ocean be at least realistic?

The tropics I think would be fraud as a basis for carbon offsets because the fertilization would have happened anyway, eventually, naturally. I guess I could imagine the concept working as advertised in the deep Southern Ocean. Not so easy to fertilize down there, but if you manage to fertilize it, you will accomplish something that wouldn’t have happened anyway.

But the change in carbon chemistry of the ocean and ultimately the atmosphere need to be transparently documented, also, if we are to trade carbon offsets based on iron fertilization. Documenting a change in carbon content of surface waters might be possible in the tropics, but it would be a nightmare in the Southern Ocean, probably impossible to do reliably. Ocean chemistry data is generally cleaner than land data, less susceptible to local variability. In tranquil, well-behaved parts of the ocean like near the Galapagos, it would be probably easier to document changes in the carbon content of the upper ocean than it would be on land. On the other hand, the ocean moves around a lot more than the land does, in general. The Southern Ocean, in particular, is a maelstrom. Tracking a plume of fertilized water to measure the change in carbon content would be a mite trickier.

Southern Ocean surface water also has a harder time changing the CO2 concentration of the atmosphere, because it gets mixed into the interior so quickly. Ultimately it would take centuries to bring the atmospheric CO2 to a new equilibrium value. You would have to wait until your fertilized water filled up the entire deep ocean. I think the long time scale also means that a ton of carbon removed from Antarctic surface waters does not translate to a ton of carbon removed on some reasonable timescale from the atmosphere. The efficiency is much lower than that, and difficult to document.

I would put ocean fertilization on the avoid list, along with planting trees. It’s too hard to pin down the actual amount of CO2 removed from the atmosphere by your actions. It’s also not a long-term solution, since the ocean leaks. Humankind would have to keep fertilizing the ocean indefinitely in order to preserve the claimed CO2 drawdown. If you’re concerned about climate change, build a windmill. Ocean fertilization does not seem to me suitable to be the basis for a reliable financial commodity, or a practical tool for geo-engineering climate.

David Archer

Blain, S. Effect of natural iron fertilization on carbon sequestration in the Southern Ocean. Nature, doi:10.1038/nature05700, 2007.
Marinov, I. The Southern Ocean biogeochemical divide. Nature, doi:10.1038/nature04883, 2006.
Pacala, S. and S. Socolow, Stabilization Wedges: Solving the Climate Problem for the Next 50 Years with Current Technologies. Science 305: 968-972, 2004.
Zeebe, R. and D. Archer, Feasibility of ocean fertilization and its impact on future atmospheric CO2 levels. Geophys. Res. Letters, doi:10.1029/2005GL022449, 2005.

137 Responses to “Thin Soup and a Thin Story”

  1. 1
    brainworms says:

    Sounds idiotic to me. Climate change is happening because of man’s mucking around with his environment. Seeding the ocean with plankton would only open yet another can of worms. Humans are the one species that has a choice to be either parasitic or symbiotic. Obviously we’re making the wrong choice. That’s what needs to change.

  2. 2
    Joe Otten says:

    I don’t quite follow this argument:

    “The problem with the tropics is that if tropical surface waters are destined to remain at the surface for a while, they are also probably destined to ultimately scrounge the iron they need, … So what’s the point of paying for a carbon offset to fertilize a water parcel now, when nature would fertilize it soon anyway?”

    Yes, a certain volume of water may get fertilised eventually anyway, but by fertilising it now can’t we speed up the rate and thereby increase the general rate of carbon capture by the oceans? That is can we turn a slow process with a low throughput into a faster one with, therefore, a higher throughput?

    [Response:CO2 accumulates in the atmosphere, so ideally we should be looking for permanent or at least long-term removal, rather than a transient fix. For methane, a transient gas in the atmosphere, a temporary fix would make more sense. David]

  3. 3
    Ms. Krieger says:

    That company, Planktos, is becoming ubiquitous–their representatives show up at all sorts of climate change meetings and conferences and try to convince anyone they can pigeonhole that their idea is a good one. Their concept gets play only because of their non-stop self-promotion. I, for one, hope they are unsuccessful. There’s far better things to be spending money on.

  4. 4
    Timothy Chase says:

    I would put ocean fertilization on the avoid list, along with planting trees. It’s too hard to pin down the actual amount of CO2 removed from the atmosphere by your actions. It’s also not a long-term solution, since the ocean leaks. Humankind would have to keep fertilizing the ocean indefinitely in order to preserve the claimed CO2 drawdown. If you’re concerned about climate change, build a windmill. Ocean fertilization does not seem to me suitable to be the basis for a reliable financial commodity, or a practical tool for geo-engineering climate.

    Yes, the idea reminds me of the following…

    Expert: Ever since 2063, we simply drop a giant ice cube into the ocean every now and then.

    Lisa: Just like Daddy puts in his drink every morning. But tEhen he gets mad.

    Expert: Of course, since the greenhouse gases are still building up, it takes more and more ice each time. Thus solving the problem once and for all.

    Global Warming, or None Like It Hot! (Simpsons episode featured in “An Inconvenient Truth”)

  5. 5
    Jim Redden says:

    To paraphrase something attributed to Aldo Leopold: it seems that when we attempt to manipulate nature, it is akin to poking a screwdriver within the mechanism of a clock; while there is a very slight chance of improvement, more than likely we will be worse off than we were before.

    For a host of factual reasons, I am incredulous of the long term efficacy of most all carbon offset programs. About a year ago I was asked about an investment solicitation for Planktos, and wondered…. Perhaps the best way to sequester carbon from the atmosphere is to bind carbon with water and put it in the deep ground–oh wait, that is petroleum–never mind.

    On another note, Science has a related article, Revisiting Carbon Flux Through the Ocean Twilight Zone,

    that is reported also reported on here

  6. 6
    Stephen Leiper says:

    More importantly, there’s the problem of acidification in such schemes. I refer you to the 2 Jul 2005 RealClimate article: The Acid Ocean – the Other Problem with CO2 Emission

  7. 7

    If they do manage to sink the carbon, won’t they also sink the other nutrients and so turn the oceans into a desert?

    [Response:Sure, that’s the mechanism by which fertilizing one area of the sea surface could diminish the fertility elsewhere. David]

  8. 8
    Karen Kohfeld says:

    I’m very happy to see realclimate take on this topic, especially since buying up carbon credits will soon be all the rage, and there is a real danger in lots of dollars being thrown at questionable carbon sequestration projects. When I give talks on the glacial-interglacial contributions of plankton to CO2 fluctuations, I’m frequently asked about planktos. Specifically, how much carbon would be produced in order to sequester CO2. I can speak to the uncertainty of how much carbon could actually be sequestered, but I’m ignorant of the carbon costs of constantly taking ships out to fertilize/monitor the ocean – has anyone made estimates of that side of the equation?

  9. 9
    FishOutofWater says:

    Fertilization is utterly useless.

    Why? CaCO3 precipitation removes Ca++ from the water, shifting the carbonate buffer towards higher acidity. The higher acidity of the ocean reduces the uptake of CO2 by seawater and the rate of additional CaCO3 precipitation by biological activity.

    So, what appears to be beneficial in an experiment, or for a few years of fertilization becomes utterly useless when applied on a time frame greater than maybe 10 years or so. I haven’t done calculations, so I’m guessing at time frames, but the principle is correct. Fertilization is a waste of time and money. It is a mirage.

    [Response:It’s true that production of CaCO3 actually drives the CO2 pressure up, by shifting the pH of the seawater toward the acidic. But plankton communities produce more organic carbon than CaCO3, by a factor of 4 to 10 or so (the exact number is not well known). So the CO2 drawdown by the organic carbon production outweighs the Co2 boost from the CaCO3 production. David. ]

  10. 10
    Hank Roberts says:

    Offsets are often bogus.
    This article points out that simply lying about them isn’t illegal:

  11. 11
    Floccina says:

    To those who fear human any human intervention in the environment on principle you must consider that we humans have been radically changing the environment for hundreds if not thousands of years and so far most of the changes have been good for humanity.


    Making terra preta(or agricultural charcoal seems to be a promising carbon sequestration scheme.

    BTW I think that it is important to keep comming up with and cross examining new ideas.

  12. 12

    And ad to this that the effect might be cancelled by CH4 and N2O going from the ocean in to the atmosphere.

    “There is a danger of creating oxygen-deficient areas in deeper and adjacent waters resulting from increased microbial respiration. The study of Orr and Sarmiento (1992) suggests that this is likely if their figure of only 0.44 Gt C yr-1 is sequestered by macroalgal farms. Not only does this have important implications for the use of the ocean as a food resource, there is also the potential for increased fluxes of CH4 and N2O from the ocean to the atmosphere (Fuhrman and Capone 1991). Both of these gases are greenhouse gases (see introduction) and might well counteract any benefits accruing from CO2 sequestration.”

  13. 13
    Steve Horstmeyer says:

    Iron fertilization has a great future IF we genetically engineer a gigantic coccolithophore. The super-sized coccolith will produce massive calcium carbonate plates and if the genetic engineers are sufficiently talented to minimize pore space – density will be maximized and so too the rate of sinking thus maximizing carbon sequestration.
    An added side effect benefit in our fight against global warming due to anthropogenic greeenhouse gasses is a great increase in the production of dimethyl sulfide or DMS. DMS oxidizes to sulfates which make efficient cloud condensation nuclei, increasing both the amount of cloud cover and the reflectivity of individual clouds. A double whammy in our fight! Again a human problem with a human solution. Is it not better to treat the source problem than blindly modify components of a natural system? When will we learn?

  14. 14
    Hunter says:

    Interesting that when self important “climate scientists” post stories to blogs about articles that are one sided they get incredibly self-important and dismissive. I especially love the almost verbatim stealing of outdated arguments from scientific journals. The simple fact is that while iron fertilization experiments have been taken place for nigh on twenty years thanks to the late John Martin’s iron hypothesis, none of these experiments have lasted long enough or been conducted on a large enough scale to effectively measure the entire life of a pleagic phytoplankton bloom, artificially fertilized or naturally occuring. The scale that planktos is talking about is many times larger than any other previous experiment, and their experiment is ultimately a scientific one. These blooms need to be studied in order to gain sufficient knowledge about their nature and the subsequent viability of CO2 sequestration. Furthermore, anthropogenic development of land has caused the amount of iron-rich dust to decrease a significant mount, and the frequency and size of plankton blooms has decreased markedly in the past decades (ref. SeaWIFS). Without delving too deep into the realm of geo-engineering, re-seeding the ocean with iron on a scale much smaller than natural for scientific purposes is a worthwhile endeavour. This article completly ignores the other company attempting to fertilize blooms, Climos, whose board is filled with very well paid talking-head figures more in it for the money than the science. I for one am very pleased that a company like Planktos is taking a much debated subject and moving it out of the blogosphere and into the realm of hard science in the same vein as the many experiments that have come before it. If we’re all lucky some very real solutions can come from this project, the proceeds of which can be re-invested in carbon-neutralizing and eco-restoration projects.

    [Response:Bottom line: Even if planktos is successful at fertilizing the ocean, I don’t believe it will impact atmospheric CO2. That’s a modeling result, every study says the same thing. David]

  15. 15
    saveEarth says:

    “We know that climate change is happening. But can it be stopped? George Monbiot’s book “Heat” shows how it can.”
    Heat review

    Related: Monbiot youTube video on HEAT launch speechMonbiot blog


  16. 16
    Al Bedo says:

    Of course increasing biomass reduces planetary albedo.

    Ocean biota increase may mean more solar absorbed
    – causing global warming!

  17. 17
    david kubiak says:

    The big story missed by both reporters and commentators alike on this subject thus far is that plankton restoration is not just about carbon credit economics or the threat of global warming. It’s about an already ongoing catastrophic die-off in the sea. The establishment science community studies cited below are only a sample of recent research indicating that the ocean phytoplankton which produce nearly 60% of the planet’s oxygen, sequester an equal measure of its CO2 and feed every higher form of ocean life are disappearing at a shocking rate. Just since 1980 we have lost 6~12% of these vital plants globally and according to Behrenfeld’s 12/06 Nature report there are now 50% die-offs in huge areas of the equatorial Pacific.

    [Response:The biota of the ocean are truly under attack by fishing and by runoff of coastal nutrients. There have been changes in the balance between nitrogen and phosphorus limitation in the Atlantic, due to nitrate deposition (a component of acid rain). I have heard it predicted that the ocean is reverting to a pre-Cambrian world of slime and jellyfish. But changes in dust deposition are not the primary culprit. David]

    (The knock-on effects of this decline are immediate and tragic. The phytoplankton-dependent krill populations in the Southern Ocean which are the staple food of all the great baleen whales are now down by 80% and the shortfall is now also starving local fish species, penguins and seals.)

    Restoring open ocean plankton populations to known 1980 levels of health would not only annually sequester at minimum 3~4 billion tons of atmospheric CO2 (or half our global warming surplus today), it would regenerate tens of billions of tons of missing nourishment for fisheries, seabirds and marine mammals.

    And this restoration can be quickly and affordably accomplished, just by replenishing missing iron micronutrients to the sea. The iron was traditionally delivered to the open ocean in wind-borne dust from arid lands which has now been depleted by 30% or more by modern agricultural practices and the increased levels of atmospheric CO2 (which allow grasses to live longer, spread further, and anchor more iron-rich topsoil dust).

    Each molecule of iron returned can fix over 100,000 molecules of CO2 and generate a proportionate amount of nutritive biomass. While nearly 80% of that is recycled in the marine food web, 20% or more disappears into the deep ocean for centuries or millennia.

    In other words, at maximum efficiency it would only take several hundred thousand tons (or about two supertankers full) of iron dust to restore the lost plankton to 1980 levels and solve half our global warming surplus, too. More likely until the technology is perfected, it will take a small fleet of research ships working with several times more dust to accomplish this task, but still we are talking a very feasible challenge that would at most be reseeding less than 2% of surface ocean waters.

    If we undertake this for the benefit of sea life and the climate and stop at the known 1980 baseline, where is the harm? Iron restoration simply replenishes a vital micronutrient that human activity has dangerously diminished.

    We have caused these crises and to attempt to resolve them in most natural and benign way available is not geoengineering, it’s generally known as restitution, healing or just merciful common sense.

    It’s gratifying that the carbon credit market has arisen to underwrite the needed restoration activity, because no one was lifting a finger or spending a cent to address these die-offs before. If you oppose restoration now simply because it may finally be both possible and profitable, you might as well also oppose the practice of medicine, environmental law and public health.

    NASA News, September 16, 2003
    “This research shows ocean primary productivity is declining, and it may be a result of climate changes such as increased temperatures and decreased iron deposition into parts of the oceans. This has major implications for the global carbon cycle,” Gregg said. Iron from trans-continental dust clouds is an important nutrient for phytoplankton, and when lacking can keep populations from growing… the amount of iron deposited from desert dust clouds into the global oceans decreased by 25 percent over two decades. These dust clouds blow across the oceans. Reductions in NPP in the South Pacific were associated with a 35 percent decline in atmospheric iron deposition.

    The amount of carbon absorbed by plant plankton in large segments of the Pacific Ocean is much less than previously estimated, researchers say. US scientists said the tiny ocean plants were absorbing up to two billion tonnes less CO2 because their growth was being limited by a lack of iron.

    By JR Minkel, Science News
    Phytoplankton in the Pacific Ocean are starved for iron, and as a result these microscopic plants soak up less of the greenhouse gas carbon dioxide than was previously thought, researchers have found.

    SYDNEY: Plankton – the vital first link in the food chain of the seas – will be hugely affected by global warming, a new U.S. study suggests. Plankton forms the main food of many ocean species, and fisheries could be badly hit by the loss of these micro-organisms as a result of warmer waters, according to the paper, published this week in the British journal Nature… Other factors that influence phytoplankton growth include [iron] dust blown from the land, and variations in solar radiation.

    Nature, Vol 446|26 April 2007| doi:10.1038/nature05700
    The efficiency of fertilization, defined as the ratio of the carbon export to the amount of
    iron supplied, was at least ten times higher than previous estimates from short-term blooms induced by iron-addition experiments. This result sheds new light on the effect of long-term fertilization by iron and macronutrients on carbon sequestration, suggesting
    that changes in iron supply from below�as invoked in some palaeoclimatic and future climate change scenarios11�may have a more significant effect on atmospheric carbon dioxide concentrations than previously thought.

    26 April 2007
    Dead plankton does not sink at the same rate everywhere in the Pacific Ocean, say researchers. The new findings will boost our understanding of the supply chain to the world’s biggest carbon sink – the bottom of the ocean. [Shows 20~50% of dying plankton take their carbon below 1000 meters into the millennial sequestration zone.]

  18. 18
    FishOutofWater says:

    Clue to David Kubiak:

    The dust bowl was not natural. It was a man made catastrophe. Modern farming practices have reduced the amounts of dust added by farming activities. Soil loss is not a good thing because degraded soils produce less food. To imply that soil loss is good for us ignores the “minor issue” of our food supply.

    Temporarily increased rates of lime deposition by fertilization are completely offset over the long-term by decreased CO2 uptake into the ocean and lower rates of precipitation of limestone by coral reefs, etc. It’s a simple mass balance problem. There is no free lunch.

  19. 19
    tico89 says:

    It’s not really my area, but I was always of the impression that the world’s oceans are an incredible balancing act, and by getting one species to proliferate, the whole ecosystem could be, to put it scientifically, ‘screwed up’. If plankton suddenly take off, won’t they be using up oxygen that will therefore cause other species to die off? I know this happens with algae and fertilisers that leach into water, but would it be a similar situation here?

  20. 20
    Fergus Brown says:

    The only geoengineering concept (assuming it fits into the same category as the above), that looks the slightest bit feasible to me is Bower/Choularton/Latham et. al.s’ cloud propagation through seawater spray. I presume it has received little support as of yet because you can’t offset carbon with it. Yes, if it worked it would be a ‘temporary fix’, but it could buy some useful time, if temperature increases were at the upper end of the estimates and the time-scale, as Hansen has suggested, is reaching critical.

    I don’t know how markets could make money out of it, so I expect it isn’t likely to be popular, even if it is effective.

  21. 21
    Aaron Lewis says:

    There was a time when the natural cycle of most bodies of water involved carbon sequestration. Inorganic nutrients were carried down the Mississippi, and supported abundant plant growth along what is now the Louisiana coast, and the subsequent year’s sand and sediment buried the material. In those days, The Sacramento Delta was laying down layers of peat, and San Francisco Bay was laying down alternate layers of organic material and sand. Now we are eroding the Gulf Coast wetlands faster than they are being formed. Peat is not forming in the Delta due to current water management practices. San Francisco Bay is urbanized, and when trees fall into the Bay, the trees are picked up by the debris collector before they became water logged and sink to the bottom of the Bay. So humans have changed carbon sequestration patterns, as well as releasing carbon from coal deposits.

    Where we do sequester carbon is in our landfills. If everyone in the world would just diligently discard 4.27 pounds of carbon into their land fill every day the global green house gas problem would be solved. Aw, come on! It is at least as good an idea as planktos!

    These planktos guys are not selling environmental responsibility, they are just trying to make a lot of money. They think they are the smartest guys in the room.

  22. 22
    James Killus says:

    It might be worth trying to establish fisheries via iron fertilization. That would be a rather grand experiment in “eco-engineering” akin to growing crops in a desert, with the same sort of attendant risks. Still, since world-wide fish harvesting has peaked and is in decline, it might be possible to get some of the Pacific fishing nations to chip in for a large scale test.

    The main advantage of such a scheme would be the fish, of course. You’d still be recycling most of the carbon into the atmosphere in the same way crops are recycled. But there might be some limited sequestration benefits somewhere along the chain.

    [Response:I read somewhere the interesting idea of pumping deep water up to the surface, mining the nitrogen and phosphorus to support aquaculture. David]

  23. 23
    Geoff Russell says:

    Slightly off topic but related to ocean update of CO2.

    From Hansen and Sato 2004 “Greenhouse gas growth rates”
    “Consider the following gedanken experi-
    ment. Case A: CO2 increases by an amount ( 16 ppm) that causes
    a climate forcing of 0.25 W m2, whereas CH4 decreases by an
    amount ( 0.5 ppm) that causes a climate forcing of 0.25 W m2.
    Case B: CO2 decreases so as to cause a forcing of 0.25 W m2,
    whereas CH4 increases to cause a forcing of 0.25 W m2. Cases A
    and B both yield no net forcing and thus no tendency for a climate
    change. However, case A has practical advantages.
    One advantage of case A is that CO2 is removed from the
    atmosphere at a faster rate. Stated differently, the climate is in
    equilibrium (no warming) with a larger anthropogenic CO2 source.
    The larger amount of CO2 in the air in case A causes the ocean and
    biosphere to remove CO2 at a higher rate. Atmospheric CO2 is
    greater in case A than in case B, but climate forcings are identical.”

    Why does higher co2 in the air cause higher removal of co2 by the oceans?

    I have also heard that the oceans will absorb less co2 when heated (but
    can’t remember where I heard that), which appears to contradict Hansen.

    [Response:Methane is a transient gas, so I’d trade a W/m2 of CO2 for a W/m2 of methane any day. It’d go away in a decade, while CO2 lasts for millennia. David]

  24. 24
    WJ says:

    I enjoyed reading David’s article and the comments and do not mean to deflect the discussion. However, it was shown that significant amount of DIC and DOC may be exported from ocean margins to the open ocean (Cai et al. 2003). One may suggest that ocean carbon sequestration can proceed more effectively through the uptake of atmospheric CO2 by intertidal marsh grasses and the subsequent export. This is because, unlike plankton which takes CO2 from seawater and releases back most of it after its demise, marsh grasses take CO2 from the atmosphere and the resulting C (DOC, POC, DIC) stays in the water. Note that we do not know yet how much that water and C will get to the deep ocean.
    Cai, W.-J., et al. 2003. The role of marsh-dominated heterotrophic continental margins in transport of CO2 between the atmosphere, the land-sea interface and the ocean. Geophysical Research Letters 30, 1849.

  25. 25
    Ike Solem says:

    It also appears that there are decreasing rates of bottom water formation; that means that oxygen input to the deep ocean is probably decreasing… is it possible that we could be pushing the global oceans towards a state where bottom water anoxia is much more prevalent? Do we want to push this process along? (It does seem that such a response would take several thousand years, though there might be more hypoxic regional effects similar to what’s been happening off of Oregon’s coast each year)

    The whole issue of the phytoplankton role in the carbon cycle is still poorly understood, and recent research indicates that most photosynthetically fixed carbon is simply recycled in the water column. See for example Oceanic Twilight Zone Plays Important Role In Climate Change and

    In addition to this excellent RC article, there is another good review of this issue by Chisholm, Falkowski and Cullen (Sci 2001) available in pdf form: Dis-Crediting Ocean Fertilization, Sci 2001. To quote:

    Given all of the risks and limitations, why has the idea of industrial scale ocean fertilization not been summarily dismissed? One answer lies in carbon trading (5). One need not fertilize entire ocean basins to sequester an amount of carbon that could yield commercial benefits on this anticipated market. If scientifically sound verification criteria could be developed, relatively small scale fertilizations could be very profitable for individual entrepreneurs.

    There doesn’t seem to be any way to get around the fact that we’ll have to voluntarily stop burning fossil fuels within the next few decades if we want to aim for the lower end of possible warming scenarios. The facts seem pretty clear: ocean iron fertilization as a CO2 mitigating process is a fraud.

  26. 26
    Ken Caldeira says:

    In addition to David’s point about efficacy, I think there is an additional point about goals.

    It seems to me that a primary reason to prevent human-induced climate change is to protect and preserve natural ecosystems. Ocean fertilization works by manipulating natural ecosystems on a grand scale, so rather than protecting these ecosystems we are disturbing them in yet another way.

    When climate change is viewed too narrowly as a goal, all kinds of perverse incentives can arise. For example, it could be argued that cutting down boreal forests can slow climate change. Both ocean fertilization and boreal deforestation could potentially slow down global warming a bit, but at the expense of disturbing or destroying vast natural ecosystems. If we look at prevention of human-induced climate change as a means to achieve the broader goal of preserving our natural environment, then schemes to slow global warming that rely on environmental degradation would be seen not to serve our broader goals.

  27. 27
    jim Thomas says:

    David Kubiak fails to mention that he is the Communications and PR officer at Planktos.

    The IPCC is expected to strongly dismiss geo-engineering schemes and ocean fertilization in particular in the Working group III report on mitigation this week. They are absolutely right to do so- it is neither a scientifically or morally right approach to solving the climate crisis. For those who are interested see news release below.


    Jim Thomas
    ETC Group

    News Release
    ETC Group
    May 3rd, 2007

    Geo-engineers to Foul Galapagos Seas – Defying Climate Panel Warning.

    As the UN’s top climate science panel, the IPCC, prepares to criticise the idea of geo-engineering, one maverick geo-engineering company, Planktos Inc, has announced it is about to dump several tonnes of tiny particles into the waters around the Galapagos Islands, covering an area larger than Puerto Rico. Doing so, they claim, will re-engineer the atmosphere, win them commercial carbon credits and perhaps a shot at the $25 million prize for greenhouse gas reduction put up by Richard Branson. Mainstream scientists are sceptical and environmental and social justice groups are crying foul.

    “In a sensible world geo-engineering fanatics like Planktos would have their license to operate taken away.” says Jim Thomas of ETC Group. “Instead, they are being allowed to pollute the high seas and are even being considered for a prize! Climate change is a real threat but common sense should not be its first victim.”

    On May 4th the International Panel on Climate Change, a body of the world’s leading climate scientists will publish policy recommendations to governments on how to mitigate global warming. According to an article from Agence France Presse (AFP) who have seen a leaked draft of that report, the panel gives the “thumbs down” and “pours scorn” on a clutch of wacky plans to intentionally re-engineer large scale ecosystems, referred to collectively as geo-engineering: “Geo-engineering options… remain largely speculative and with the risk of unknown side-effects” claims the IPCC draft according to AFP (1). The US government has reportedly been lobbying the IPCC to more prominently support geo-engineering technofixes in order to sideline the Kyoto Protocol(2).

    However, even as the UN report becomes public this Friday in Bangkok, one commercial enterprise, California based Planktos Inc, will be sailing from Florida to carry out a large-scale geo-engineering experiment. Planktos, a self-styled “eco-restoration” firm that also doubles as a nuclear fusion company(3), intends to dump tens of tonnes of tiny iron particles over 10,000 square kilometres of ocean around the Galapagos Islands at the end of May 2007. By stimulating a massive growth of plankton, called a bloom, Planktos claims to be able to draw millions of tonnes of carbon dioxide out of the atmosphere into the deep oceans over the next year. Eleven smaller iron fertilization experiments have already taken place.

    “The Iron Hypothesis” is the theory first put forward by oceanographer John Martin in 1990. He believed you could cool the climate by growing extra plankton in the oceans, a process that also gives rise to cloud formation. Martin once famously declared: “Give me a half tanker of iron, and I will give you an ice age.” From drafts of the forthcoming IPCC report seen by ETC Group the UN body is expected to highlight the potential negative impacts of such iron seeding. These include increased production of nitrous oxide and methane, unintended changes in the plankton that could result in production of toxic blooms and effects on the ocean food chain. Local and international environmental groups are furious at this risky gamble with sensitive marine ecosystems spurred by the profit-making incentive of market-based carbon trading.

    “This is an irresponsible and unpredictable venture by purely profit-driven individuals,” said Elizabeth Bravo of Ecuador-based Accion Ecologica “It threatens our climate, our marine environment and the sovereignty of our fisherfolk and it should be stopped.â�� The Galapagos Islands are a UNESCO world heritage site under the sovereignty of Ecuador.

    “Climate change should to be tackled by reducing emissions, not by altering ocean ecosystems,” said Dr Paul Johnston, Head of Greenpeace International’s Science Unit, “Planktos is intending to conduct this reckless experiment in waters around the Galapagos Islands which are globally significant in biological terms and should be designated as fully protected marine reserves.”

    Last week the science journal Nature published a study on iron seeding authored by forty-seven ocean scientists.(4) They concluded that such attempts to artificially seed the ocean were unlikely to sequester much carbon dioxide. Their results, they say, “mean the end of the ‘geo-engineering’ utopia that consists of artificially seeding the oceans with iron.”(5) As one of the scientists, Ulf Riebesell, a biological oceanographer at the Liebniz institute of Marine Sciences in Kiel Germany told Nature bluntly, “You just can’t achieve nature’s efficiency. That’s why geo-engineering the ocean won’t work.”(6) This scientific reality hasn’t deterred Planktos, which hopes to convince the market that they can sell plankton-powered carbon “offsets” to consumers to salve guilty consciences. As Planktos CEO Russ George admitted in a 2003 radio interview with National Public Radio in the USA, “It’s really more of a business experiment than a scientific experiment.”(7)

    As worrying, Planktos boasts on their website that the iron they dump will be in nanoparticle form because nanoparticles float longer than normal particles.(8) (although Planktos have given contrary information in person). If this is true, then the Planktos experiment may be the largest intentional release of engineered nanoparticles ever undertaken. The last four years have seen a growing scientific consensus that the altered properties exhibited by nanoparticles could have negative toxicity effects on the environment and for human health. In 2004 the UK�s Royal Society and Royal Academy of Engineering issued a recommendation that environmental applications of nanoparticles should be prohibited,(9) a call echoed by many environmental groups. Planktos claims they will be dumping their particles in international waters and so are not bound by international treaties or permit requirements.

    In a further twist of the ridiculous, Planktos has also invited airline billionaire Richard Branson, Chairman of the Virgin Group, to join them in the Galapagos(10). In March Branson announced The Virgin Earth Challenge, a US $25 million prize to whoever could commercially develop a working geo-engineering technology (See Unfortunately, Planktos is not the only company competing to technologically alter the climate. In February ETC Group published a report, “Gambling with Gaia”, describing a clutch of companies pursing geo-engineering business plans.
    For more information contact:

    Jim Thomas, ETC Group (Montreal, Canada)
    Tel: +1 514 516-5759

    Pat Mooney, ETC Group (Ottawa, Canada)
    Tel: +1 613 2412267

    Kathy Jo Wetter, ETC Group (Carrboro, NC, USA)
    Tel: +1 919 960-5223

    Elizabeth Bravo, Accion Ecologica (Ecuador)

    Dr Paul Johnston, Greenpeace International (Exeter, UK)
    +44 (0)1392 413019

    ETC Group’s report on geo-engineering, “Gambling with Gaia”, is available online at

    [1]Richard Ingham “Oddball schemes to fix global warming get thumbs down”, AFP, 29 April 2007.
    [2] David Adam, “US Government answer to global warming: Smoke and giant mirrors,” The Guardian, 27 January 2007.

    [3] Planktos “mirror” company D2fusion shares same most of the same management team as Planktos – see
    [4] Blain S et al, “Effect of natural iron fertilization on carbon sequestration in the southern ocean.” Nature vol. 446. 26 April 2007. 1070-1074 (2007)
    [5] CNRS: Fertiliser les oceans : la fin d’une utopie? – April 26, 2007, on the Internet at
    [6] Quirin Schiermeier, “Only mother nature knows how to fertilize the ocean – Natural input of nutrients works ten times better than manmade injections” published online in Nature, April 23, 2007. , on the Internet:
    [7] Wendy Williams “Living on Earth; Iron fertilization”, NPR, 30 May 2003, transcript at
    [8] According to Planktos, Inc. website: “…we use this material in a nano-particle form where the particles are so small that the sink rate is measured in weeks and months as opposed to minutes.” (viewed May 1, 2007).

    [9] Recommendation 5, chapter 10, Royal Society and Royal Academy of Engineering, “Nanoscience and nanotechnologies: opportunities and uncertainties” published on 29 July 2004.
    [10] Planktos News Release, “Planktos Offers Branson Chance to Help Win his own Prize”, 10 February 2007. on the Internet:

  28. 28
    James says:

    Re #17: There are a couple of points in that that immediately popped out at me. First:

    [The phytoplankton-dependent krill populations in the Southern Ocean which are the staple food of all the great baleen whales are now down by 80%…]

    The baleen whales were hunted to near extinction before the mid-20th century, and their populations have not recovered to anywhere near historic levels yet, so I have trouble seeing a link between plankton depletion and whales. Indeed, I’d expect any link to go the other way: with a major plankton consumer gone, the population should increase until it hits some other limit. So what’s happening that makes this not the case?

    Then there’s this:

    [The iron was traditionally delivered to the open ocean in wind-borne dust from arid lands which has now been depleted by 30% or more by modern agricultural practices…]

    In fact human agricultural practices have greatly increased the extent of arid lands, from which such dusts could arise. From Australia to the Sahara & Sahel to the deserts of the Middle East & northwest India to the American West, human activity has destroyed fertile grasslands, and exposed the underlying soil to erosion by winds and rivers.

    Which raises another question: if such fertilization works, you should see it happening in e.g. the Gulf of Mexico, off the mouth of the Amazon, and in other places where rivers deposit lots of sediment.

    [Response:I agree with your point about the whales. But on your question, the answer is that you do see a land fertilization effect. The Galapagos themselves leave a lovely green wake in the ocean as viewed by satellite ocean color scanner. David]

  29. 29
    Ryan Sullivan says:

    Thank you for a very nice article on a fascinating topic that has captured my interest in the past few years. You briefly mentioned dust as a source of iron. I think it is important to remind people about this sporadic, though natural source of iron to the oceans. Jickells nicely reviews our understanding and the numerous major questions remaining in this topic:
    Jickells TD, An ZS, Andersen KK, et al.
    Global iron connections between desert dust, ocean biogeochemistry, and climate
    Science 308 (5718): 67-71 APR 1 2005

    Anthropogenic activities can modify the natural source of iron from dust to HNLC ocean regions, by increasing desertification, and by producing acidic gases such as SO2 which can react with and solubilise the iron in mineral dust particles. My own research has explored the later issue of dust mixed with sulphuric acid, e.g.:
    R. C. Sullivan, S. A. Guazzotti, D. A. Sodeman, and K. A. Prather
    Direct observations of the atmospheric processing of Asian mineral dust
    Atmospheric Chemistry and Physics 7: 1213-1236, 2007.

    I hadn’t really considered the important point of how effectively the increased biomass is exported down through the water column so that it becomes a long-term sink for carbon and is not quickly recycled back to the atmosphere.
    I think it is also important to point out possible feedbacks on cloud cover through ocean fertilization. Increased biomass can lead to increased emissions of biogases such as dimethyl sulfide and isoprene, which when oxidized in the atmospheric form sulphate and organic aerosols that can nucleate clouds, increasing cloud cover and planetary albedo – the CLAW Hypothesis.


  30. 30
    david kubiak says:

    Response to fishoutofwater: was not recommending a return to slash & burn ag and dust bowl days, simply pointing out that human civilization has already been the biggest, most aggravating geo-engineering experiment the biosphere has ever endured, and it’s time to apply some first aid and emergency care to its most important life-sustaining victims.

    Comment to tico89: Likewise nobody is talking about pushing plankton to unprecedented limits, we are just saying bring them back to their previous normal levels and stop right there. Their scarcity is starving everything else in the neighborhood and their revival would simply restore the food chain we have lost.

    If we don’t something – indeed many things – soon the Royal Society projects that we will have no ocean fish at all by 2048. No ocean fish = no penguins, no sea birds, no dolphins, no seals, no whales, no…

    Just can’t understand the persistant resistance to recognizing what havoc we have caused in the sea by depriving it of vital micronutrients and the unwillingness to make the relatively minor effort it would take to make it whole again. Except for the bacteria, absolutely everything living in the sea depends on these little guys as well as nearly 60% of our oxygen. You kiss them off at your/our eternal peril…

  31. 31
    Mike Donald says:

    This morning 3 May ’07 John Humphreys on Radio 4 (listened to by a large proportion of Brits every morning) picked up the story from the Independent. So this story might get some momentum behind it and make people less inclined to reduce CO2 emissions.

  32. 32
    Alvia Gaskill says:

    Sorry about the duplicate post. There was something wrong with the website when I sent this originally. Perhaps the backlog of other posts. It also failed to include a key sentence regarding the loss of diatoms due to insufficient silicate in the water.

    Once the silicate in the water is used up, the population of diatoms will drop and you will no longer have the same distribution of phytoplankton species. That alone may be unsatisfactory in that replacing the diatoms with other phytoplankon may wreck the relationship between phyto and zooplankton and create an entirely new ecology that may be unfavorable for sustaining the oceanic food chain.

  33. 33
    Killr0y says:

    Why don’t we just use atmospheric water generators (essentialy very large dehumidifiers) to suck some of the water vapor out of the atmostphere.. You know, the same water vapor that is responsible for 90% or so of the actual Greenhouse effect. Once the global temperature is stabalized, we can play with biological & chemical CO2 scrubbers. Lets get this weather fixed FIRST, and worry about fixing the underlying problem (or what we think it may be) secondary.

  34. 34
    Ian Perrin says:

    Re #11

    “Making terra preta(or agricultural charcoal seems to be a promising carbon sequestration scheme.”

    This does look really promising, though at a very early stage. Would the RC team care to comment?

  35. 35
    Mark says:

    It seems far easier to dump a bunch of soil, nutrients, and industrial organic waste down our rivers. Reform starts in our own backyards.

    If we are able to overload the system and maximize productivity within rivers, deltas, and their freshwater plumes — it should be possible to completely deplete dissolved oxygen in near shore waters and give carbon the best chance possible for preservation and burial. Maintaining deep water ship canals in deltas should have the added benefit of transporting sediment to deep waters instead of delta plains where it might later get reworked and oxidized.

  36. 36
    Alan says:

    RE #13:

    I do not for a second belive that krill production in the southern ocean is “down by 80% on 1980 levels”. As for dust the only significant bits of exposed land that come close to the southern ocean are Australia and the tips of S.America and S.Africa. Australia is by far the largest exposed land mass and in case you hadn’t noticed has been suffering it’s own “dustbowl” for up to 10yrs in the south and SE, (not to mention a large chunk of Australia is iron rich desert). I have lived in Australia for 45yrs and even in the southern city of Melbourne we are used to seeing duststorms in mid-late summer. For the past 5yrs everything has been regularly covered with a coat of red dust ALL YEAR ROUND. Just ask the New Zelander’s how much of our red dust lands on their country on it’s way to directly to Antartica. I really don’t think a hypothetical collapse of plankton from an imaginary lack of red dust is a problem.

    According to a large scientific survey of the southern ocean (carried out by CSIRO and others), plankton blooms are created naturally in the deep ocean to the south of Australia because of a huge undersea canyon that starts below Tasmania and curves NW towards the Indian ocean. Deep and powerfull currents run along the bottom of canyon randomly hiting undersea bluffs that force the nutrient rich water to the surface. Another current runs south down the east coast and mixes with this current below Tasmaina creating edies that also spur plankton growth.

    Part of the CSIRO’s study of the southern ocean as it relates to iron dust, carbon emmisions and plankton can be found here. I think Dr.Trull hits the nail on the head with this understatement: “It is a very complex process that we don’t completely understand yet”.

    These blooms off the southern coast of Australia are the only place in the world where blue whales can be spotted gulping 50ton mouthfulls of water and krill, where they go after feeding is a mystery. As more and more fisheries collapse around the world, the very real threats to the southern ocean’s ecology over the next few decades are acidification from dissolved C02 and overfishing. The prized catches of patagonian toothfish and blue fin tuna are already in rapid decline and are regularly poached from Australian waters by large factory ships from as far away as Norway.

  37. 37
    Alan says:

    Opps, sorry to post twice but my previous comment was in reply to #17 not #13.

  38. 38
    chapter1 says:

    David wrote:

    > I would put ocean fertilization on the avoid list, along with planting trees

    Sorry for somewhat off-topic post, but could someone please point me to some background on the problems w/ planting trees? I understand that their affect on albedo is unfortunate, and their affects on transpiration/evaporation/cloud cover are ambiguous, but aren’t these outweighed by their sequestration benefits, especially at low-latitude or even low-ish latitued (e.g., Israel)?

    Thanks in advance!

    [Response:I just don’t want to pay to reforest land that was just recently cut, and I don’t want to pay to plant trees today that will be cut tomorrow. I don’t believe that the carbon accounting is very reliable. David]

  39. 39
    Jenn says:

    If you add more iron into the ocean to encourage phytoplankton growth, how do you make sure you avoid a toxic bloom of species (e.g. red tide) that create anoxic zones and may have the potential to harm other species populations? It sounds like pulling this off successfully without negative side effects would be quite the delicate act. Is the current scientific knowledge of these processes well established enough to have the confidence for this company to carry this out appropriately and successfully?

  40. 40
    Sean O says:

    First, let me start by saying I am not a marine biologist. I run a blog on the subject of global warming “Is It Getting Warmer?” and I regularly come to this site to learn more and then try to simplify this science for my readers. I have a huge amount of respect for this site but I know that many people cannot touch the science that is discussed here. I rarely post on this site but feel compelled to based on comment #13 above, specifically the following paragraph:
    “Restoring open ocean plankton populations to known 1980 levels of health would not only annually sequester at minimum 3~4 billion tons of atmospheric CO2 (or half our global warming surplus today), it would regenerate tens of billions of tons of missing nourishment for fisheries, seabirds and marine mammals.”

    Please indulge me as we take a logic tour based on this one paragraph:
    CO2 levels are up world-wide.
    Plankton is down significantly since 1980.
    Restoration of plankton to 1980 levels would scrub half of the human caused CO2 out of the atmosphere.
    Obvious question: Is the excess CO2 problem caused by humans or the fact that plankton population is diminished (I understand that the plankton population may also be affected by human behavior).
    Next obvious question: If the above question is true (and I am not saying that it is) why in the world would we be investing billions in alternative and questionable energy sources and energy uses when we should be spending billions in fixing the root cause of the plankton problem (stress the phrase “root cause”).

  41. 41
    Sebb says:

    On another tack to mitigation – does anyone have any insight or data on man-made albedo? The albedo of cities is higher already, what if we mandated white roofs? I can see two effects – reduced need for A/C (one estimate I saw was 6-10 tons of A/C (12,000BTU = 1 ton) from spraying a flat black rubber roof with water in a dry environment and letting it evaporate – but a white roof wouldn’t need spraying in the first place), and the other is from increasing reflection into space? I don’t know if low level albedo is a good or bad thing. Maybe those sheep are on to something??


  42. 42
    Dick Veldkamp says:


    You write: “I would put ocean fertilization on the avoid list, along with planting trees.”

    In my view, planting trees would at least result in sequestering CO2 now – and rather quickly. Clearly it is no permanent solution, but it buys time. Why would you want to actively avoid it?

    Let it be clear that I also want to save energy (highest priority), curb air traffic, build wind turbines etc, etc.

  43. 43
    Alan says:

    RE #40

    I’m not sure why David said that but I agree. As much as I would love to see people creating forests rather than destroying them, CO2 emmissions are a problem caused by a global market that until recently belived they could throw anything at the biosphere and it wouldn’t make a difference.

    We can still emit GHG’s but we have to wind back to a point that doesn’t significantly enhance the chances of fullfilling the “sixth great extinction” senario. The only way to do this is to first determine where that point should be and then regulate emissions as a “limited resource” in the market place.

    If you are going to regulate it seriously then people will demand it be measured seriously. Accountants can do this for smoke stacks, tailpipes, wet cement, ect by simply looking at the inputs and applying a forumla. As you seem to acknowledge yourself, nobody can measure a forests activity with anywhere near that kind of precision, accountants are known to abhor (other peoples) fuzziness and at the end of the day forests are already vastly undervalued for different reasons.

    To me the obvious (simplyfied) answer is for governments to organise a yearly global auction of X billion carbon credits that represent XGt of carbon targeted to be released that finacial year. Then with some of the money raised put the taxman in charge of policing it and monitoring it in each others nations. Eventually this cost is passed down to the most price sensitive creature in the universe, the modern consumer (after all we ARE the root cause).

    As the squeeze is put on to meet the targets the price skyrockets and people get on with the suddenly very profitable job of building windfarms, putting solar collectors on roofs and such, all with the aid of subidies that are paid for by the auctions. Money is incapable of building anything useless unless it goes around in circles and the same will be true for any carbon credit treaty.

    The same principle can be applied to trees by realizing there is some global maximum we can harvest that depends on both planting and natural growth (this has already occured in many western nations but at the expense of everybody else’s trees). The only thing stopping such pragmatisim toward our planet’s biosphere is the fact we are dealing with a very large population of “apes” that have very recently formed into a handfull of large (proxy) warring tribes surrounded by impoverished and malnourished outcasts. We have come from flinging our own dung at each other to launching ICBM’s in the blink of an evolutionary eye.

  44. 44
    John Laumer says:

    I view iron seeding like an emergency room intervention, similar to putting in a saline IV into a severely stressed patient. Done just enough to stabilize the patient until the doctor can offer a prognosis and outline a plan of care. We really should not view this option as a get-out-of-carbon-reduction-committment card.

  45. 45
    Ike Solem says:

    Planting trees is certainly a good idea, but it won’t even come close to ‘offsetting’ coal emissions, let alone the all fossil fuel emissions, and here is why:

    From : “For example, coal with a carbon content of 78 percent and a heating value of 14,000 Btu per pound emits about 204.3 pounds of carbon dioxide per million Btu when completely burned.(5) Complete combustion of 1 short ton (2,000 pounds = 909 kg ) of this coal will generate about 5,720 pounds (= 2.86 short tons = 2600 kg) of carbon dioxide”
    To convert CO2 mass to C mass, multiply by 0.25; 1000kg of CO2 = 250 kg of elemental carbon.

    It’s generally assumed that about 1/2 the mass of a tree is elemental carbon. So, how long does it take for a tree to accumulate the equivalent of one ton’s worth of coal? Keep in mind that according to, under “business-as-usual” scenarios, “World coal consumption is projected to increase from 5,440 million short tons in 2003 to 7,792 million short tons in 2015, at an average annual rate of 3.0 percent”.

    Trees don’t grow that fast; I can’t seem to find a good number – perhaps one ton every 20 years? So, using this estimate, how many trees per year would you have to plant to absorb all the CO2 created by coal combustion?

    5.4 billion tons coal= 15.4 billion tons of CO2 = 3.8 billion tons of carbon – which is about 1/2 of the 7.2 GtC produced by human beings every year.

    If we divide that 3.8 billion tons of carbon by our ‘tree uptake estimate’ (1/20th ton/year) we get a very crude estimate of 77.2 billion trees per year… and these trees will need to be watered, fertilized, and cared for to achieve that estimate of carbon fixation. That’s every year… and since coal use is increasing, that means more trees will have to be planted every year. If you want to account for all the fossil fuel emissions, double that estimate.

    Conclusion? Offsets are not feasible, and carbon trading will have little if any effect on atmospheric CO2 levels. We simply have to stop converting fossil fuels to atmospheric CO2, and use alternative energy sources.

    If you look into the matter a little more, you can see that carbon traders will not be supporting the massive replacement of fossil fuel sources by renewables – because who would buy the carbon credits in that case? Would carbon traders want to see a ‘glut’ of carbon credits on the market? The whole program is a fraud, and diverts attention from the need to switch entirely to renewables.

  46. 46
    Hank Roberts says:
    “Tracking carbon in the oceanâ��s “twilight zone”

    “UH oceanographers Robert Bidigare, director of the Center for Marine Microbial Ecology and Diversity (CMMED), and Dave Karl, director of the Center for Microbial Oceanography: Research and Education (C-MORE) are among the co-authors of a paper in the journal Science showing that carbon dioxide does not always sink to the ocean depths where it can be stored. Instead, the study says, sinking particles of carbon are often consumed by animals and bacteria in an area known as the twilight zone â�� about 300 to 3,000 feet below the surface â�� questioning the ocean’s potential impact on greenhouse gases implicated in global climate change.”

  47. 47
    Chuck Booth says:

    Re #17 [ocean phytoplankton which produce nearly 60% of the planet’s oxygen]

    Sorry to nitpick, but I’m curious to know where you got that figure of 60% – the most reliable numbers I have seen (admittedly, now nearly a decade old) for ocean phytoplankton are 45% of world net primary productivity (NPP):

    C. B. Field, M. J. Behrenfeld, J. T. Randerson and P. Falkowski (1998)
    Primary Production of the Biosphere: Integrating Terrestrial and Oceanic Components. Science 281 (no. 5374): 237-240.

    Overestimating primary production by marine phytoplankton could result in an overestimate of their potential role in mitigating AGW. Moreover, the distribution of those phytoplankton is not uniform. It seems to me that iron fertilization will likely have its greatest impact in oligotrophic regions (e.g., subtropical gyres) which currently provide less than 10% of world NPP. How much can NPP be stimulated in those regions, and what is the cost (mining and processing the iron ore, shipping it out to the middle of the ocean, etc)?

  48. 48
    Chuck Booth says:

    Re # 35 [suck some of the water vapor out of the atmosphere]

    I hope this was suggested in jest. But, just in case you were semi-serious: With oceans covering 70% of the earth’s surface, you could never change atmospheric humidity – water vapor pressure is a function of atmospheric temperature, increasing as temperature rises.

  49. 49
    Doug Heiken says:

    Trees may not last long enough to contribute to long-term carbon storage, but forests might. We need to think of average carbon storage over many cycles of growth and disturbance. Old forests that are protected and allowed to grow and recovery for long periods after fires and hurricanes would store carbon over time, more so than if those same lands were managed as agricultural fields or short-rotation tree farms. For more see:

  50. 50
    Chuck Booth says:

    # 51 long term carbon storage

    But, what happens to the carbon stored in those old trees when they finally die and begin to decay?