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To meet the Paris climate goals, do we need to engineer the climate?

Posted on 5 April 2016 by Guest Author

The climate talks that convened in Paris at the end of 2015 produced a historic agreement, giving negotiators and climate activists good reason to celebrate. Now the task is to ensure that the ambition shown in Paris is matched by action.

The good news is that there are a number of viable ways to meet the Paris climate goals. It was reported a couple of weeks ago that, since 2007, the output of the U.S. economy has grown by around 10 percent, while primary energy consumption fell by 2.4 percent over the same period. It is now possible to imagine that the economy can grow, even as fossil fuel-based energy production declines. Add to this an announcement from the International Energy Agency that electricity produced worldwide from renewable sources looks to be on track to overtake coal-fired generation by 2030, and the much-needed renewable energy revolution may well be upon us.

All is not necessarily rosy, however. For one thing, international agreements don’t always translate into domestic momentum. Witness, for instance, the decision by the Supreme Court of the United States to place a stay on a key part of the Obama administration’s plan to stem carbon emissions.

A second piece of bad news, or, at least, news that will be unwelcome in many quarters, is that matching the ambition of Paris will demand consideration of options for addressing climate change that to this point have been widely deemed unpalatable.

Our read is that the Paris agreement will, through time, force closer consideration of so-called “climate engineering” or “geoengineering” schemes. In particular, we foresee increasing attention being paid to solar radiation management (SRM) or albedo modification technologies. This is a class of speculative responses that might cool the planet by reflecting some amount of solar energy back into space before it can trapped by the greenhouse gases in the atmosphere. Leading SRM proposals include depositing reflective sulfate particles into the stratosphere or increasing the reflectivity of marine clouds via the introduction of saltwater droplets.

Such ideas have to this point been confined to the fringes of the climate change conversation. That looks set to change. Here’s why.

Energy transition is imperative (but not easy)

A critical piece of the Paris agreement is a change to the agreed “threshold” level of climate warming. The prior goal, established at the 2009 international climate meeting in Copenhagen, was for the international community to work to cap global warming at no more than 2 degrees Celsius above preindustrial averages. The new agreement is more ambitious. It urges, in the preamble, “holding the increase in the global average temperature to well below 2? above preindustrial levels and to pursue efforts to limit the temperature increase to 1.5?.”

The new target is a welcome and important development. Less warming means less risk of catastrophic sea-level rise, runaway polar and glacial ice melt, further damaging acidification of the world’s oceans and a host of other dangers.

At the same time, as critical as it is, restricting planetary warming to 1.5? amounts to a Herculean undertaking.

One recent study suggests that to limit warming to 2? via energy transition alone, more than 80 percent of coal reserves, half of all natural gas, and one-third of the world’s known oil should remain buried beneath the earth. A target of no more than 1.5? of warming means the task is that much harder. The new target rapidly accelerates the required timetable for ratcheting down greenhouse gas emissions.

The renewable energy revolution is coming, but will it come fast enough? The truth is that despite the positive intent indicated in Paris, the world to this point has shown relatively few signs that it is eager to be weaned from fossil fuels, for a few reasons.

For starters, while renewable energy availability is increasing rapidly, developed and developing countries alike are still counting on the burning of vast amounts of fossil energy to drive economic growth. Meanwhile, fossil fuel companies still play an outsized role in setting national and international priorities and policies. Breaking the hold of fossil fuels is not just a technological task, in other words. It is also an immense political and social undertaking.

Finally, it is important to note that the Paris agreement isn’t due to take hold until 2020, and even then the entirely voluntary pledges announced by countries in Paris set the world on a path to warming of 2.7? or more. Even an optimistic reading of the kinds of follow-on actions Paris might set in motion to limit warming to 1.5? suggests an extraordinarily tough road ahead.

Might 1.5C demand other forms of action?

So what more can be done? Another piece of the puzzle may be large-scale schemes to remove carbon dioxide and, perhaps, other greenhouse gases from the atmosphere and hold them in long-term storage or put them to productive use.

Capturing and then sequestering the carbon released by coal-fired power plants has been discussed for years. A number of demonstration projects have been developed or are in development. The model, though, is still not considered economically viable.

Other, more exotic ideas entail pulling carbon dioxide directly from the open atmosphere. Some of the leading proposals include bio-energy with carbon capture and storage (BECCS) and “artificial trees” that could take in and trap atmospheric carbon.

Such ideas strike some as dubious propositions. In fact, though, carbon dioxide removal (CDR) schemes are already baked into the 1.5? target. The most recent IPCC assessment report examined a wide variety of possible pathways by which atmospheric warming might be kept below 2?. Almost all of the IPCC projections required not just decarbonization of the energy economy but also the invention and deployment of what the report called “negative emissions” technologies.

Similarly, it should be noted that the Paris agreement has language not just about greenhouse gas emissions but also about greenhouse gas “removals.” The aim expressed in the Paris document, in other words, is not necessarily full decarbonization of the energy economy, but rather “net zero” emissions. That implies greenhouse gas emissions are offset by carbon removal from the atmosphere.

Yet CDR or negative emissions technologies receive comparatively little attention. That’s a misleading way to view the climate puzzle.

If the world is to meet some portion of the new Paris obligations via speculative investments in greenhouse gas removal technologies, there should be open acknowledgment of this fact, lest the world be duped by what Oliver Geden has called, in this context, “magical thinking, questionable accounting and dubious expectations about future technology.”

We need an open conversation about climate engineering proposals

As difficult and contentious as the conversation about CDR technologies promises to be, the conversation about solar radiation management (SRM) technologies will be thornier still.

A small but respected group of scientists has been calling for consideration of SRM as a third piece of the climate change response puzzle, in addition to limiting greenhouse gas emissions and enhancing greenhouse gas sinks. The argument that they make is that SRM represents the only known option that can quickly suppress temperatures, to buy time for other forms of response to take hold.

SPICE (Stratospheric Particle Injection for Climate Engineering) was a UK government-sponsored research program to investigate the feasibility of one particular mechanism by which reflective particles could be delivered into the upper atmosphere. Hughhunt, CC BY-NC-SA

There are research programs on SRM science under way at Harvard, Stanford and elsewhere. However, to date there has been next to no public attention to SRM proposals. Nor have the nongovernmental organizations that often generate public engagement been paying SRM much attention. In fact, many groups that work on climate change policy and advocacy have been studiously avoiding consideration of SRM, for quite legitimate reasons.

A major fear is that if more attention is given to this subject by more people and groups, then momentum may build in support of the project, even should negative consequences be seen to outweigh positives. The preliminary research undertaken to date suggests clear upsides to SRM development use, but also well-documented downsides. The promise of some kind of technological “fix” for climate change may also pull support from other, more needed forms of action.

At this point, though, our contention is that there is little to be gained by willfully ignoring SRM technologies.

First, the ambition of climate response expressed in Paris is driving the world toward consideration of SRM. Remember that even with the incorporation of CDR or negative emissions technologies, the models suggest that keeping temperature increases below 2?, let alone 1.5?, will be immensely difficult. If the gap between what has been promised and what materializes widens, and as climate impacts become more present and urgent, then pressure on climate decision-makers to take action will increase. Even previously outlandish plans will be on the table.

Second, and related, talk of SRM is advancing, whether people wish it to or not. At this stage, the tentative conversation about SRM is taking place largely in scientific and insulated policy circles, beyond the reach of ready public scrutiny and engagement.

This must change. In our view, the concern that consideration of SRM might be a distraction from decarbonizing the global energy system is now outweighed by the need for robust, honest and open analysis that something of this magnitude deserves. This is true, if only to make it widely and abundantly known that SRM technologies are not any kind of magical climate cure-all.

What will it mean for the world to live up to the promises of Paris? The post-Paris moment calls not just for ambition, but also an honest assessment of all the potential tools available to us. Honest assessment will generate much consternation and disagreement. Better that, however, than proceeding from a position of ignorance.

Simon Nicholson, Assistant Professor and Director of the Global Environmental Politics program in the School of International Service, American University and Michael Thompson, Managing Director, Forum for Climate Engineering Assessment, American University

This article was originally published on The Conversation. Read the original article.

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Comments 1 to 32:

  1. Maybe we could settle Mars?

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  2. SRM does virtually nothing to address the problem of ocean acidification (and actually could end up making that problem worse by justifying delayed actions on carbon emissions). 

    Ocean acidification may end up having a much worse impact on our global food supplies and food chains than warming of the globe.

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  3. Supplemental reading:

    Carbon disposal technologies are needed because incremental emissions cuts are not enough to fight climate change, says Oxford University climate scientist.

    Massive carbon capture investment 'needed to slow global warming' by Fiona Harvey & Kylie Noble, Guardian, Apr 4, 2016

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  4. John,

    Anything to avoid storing the carbon in the soil where it belongs? Sorry but as important as CO2 sequestration is needed, why spend "massive" investments in unproven technologies when actually the soil needs the carbon, and it actually is profitable instead of costing massively?

    Who wants to spend massively to pump CO2 in caves when the majority of agricultural soils worldwide are in miserable shape and desperately need that carbon? Meanwhile spending even more massive subsidies to ensure we don't  make the changes needed to get this done.? Insanity.

    You wonder why some people scoff at climate scientists and deny everything they say? It's because of ridiculous expensive unproven mitigation proposals like that.

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  5. As I’m sure has been posted here somewhere, bio fuel capture where the bio fuel is converted to charcoal and the charcoal is turned into farm land, is something people have talked about. If you use the heat from the charcoal burning you are creating energy from the hydrogen and leaving the carbon to be sequestered or used as a soil amendment. Things like that are great but I don’t think they scale up well.

    The magnitude of the problem is staggering. Isn’t it true that if we capture all the CO2 we produce and compress it to a liquid, we would fill Lake Erie in 6 years? At the same time, liquid CO2 is a commercially viable product. Isn’t the firm that was supposed to be capturing carbon from Alberta being sued because they can’t deliver promised amounts to other firms?

    So CCS is a necessary part of the picture, just not one we seem to have made much progress on.

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  6. Biochar (Terra preta) is one way but by no means the only way to store carbon in the soil.

    Pasture Cropping: A Regenerative Solution from Down Under


    "Jones calculates that 171 tons of CO2 per hectare has been sequestered to a depth of half a meter on Winona.

    Calculate that for all the wheat we produce.  Then calculate it again adding other crops like corn. The number will astonish you. Easily big enough. And istead of costly unproven technologies, it actually increases profits. Or maybe you have a problem with farmers making a profit?

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  7. dklyer @5:

    "Isn’t it true that if we capture all the CO2 we produce and compress it to a liquid, we would fill Lake Erie in 6 years?"

    Close enough.

    Taking the density of liquid CO2 at 30oC (598 kg/m3), the volume of Lake Erie (480 Km3, or 480 x 109 m3), and 2014 combined emissions of 40 GtCO2 per annum, it would take 7.18 years to fill Lake Erie.

    A figure of 6 years may be accurate if we include BAU increases of emissions over coming years.

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  8. RedBaron @6 pasture cropping is not suitable for Corn (maize).  Specifically, from your link it says:

    "The key to how pasture cropping works is the relationship between cool season (C3) plants and warm season (C4) plants—the difference being the number of carbon molecules and how they affect the process by which glucose is produced in a plant. C3 plants, such as wheat, rice, oats, and barley, grow early in the season and then become less active or go dormant as temperatures rise and light intensity increases. In contrast, C4 plants, such as corn, sorghum, sugarcane, and millet, remain dormant until temperatures become warm enough to switch on and begin growing.

    Pasture cropping utilizes the niche created by C3 and C4 plants. When a C4 is dormant (during winter), a C3 plant seed is sown by no-till drilling into the C4 pasture. With the onset of spring, the C3 plants begin to grow. If managed properly, plus the right amount of rain, the C3 crop can be harvested before the C4 plants begin the vigorous part of their growth cycle. The removal of the C3 crop will then stimulate C4 plant growth (due to reduced competition). The mix of shallow- and deep-rooted plants also access water resources in the soil differently, which can reduce competition and increase overall productivity."

    Corn, as a C4 plant, will remain dormant and grow at the same time as the grasses in the pasture, thereby eliminating the advantage of pasture cropping.  Nor will the process necessarilly be advantagious in all croplands.  Differences in rainfall periods, and annual temperature cycles may well make the method unsuitable.

    Even so, applying that value to the total land area under cerial production (including C4 cereals, so an obvious overestimate) yields the capacity to sequester 3 years of current anthropogenic CO2 emissions.  A useful contribution, but not a genuine replacement to more standard carbon sequestration schemes if they become necessary.

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  9. Tom,

    So you hypothesis is that this won't work for corn (maize). Have you tested that hypothesis? I have. You simply flip the c4 c3 backwards from the way you do wheat. Got the idea from this guy's USDA case study where he claims to be able to grow pretty much any  month, just a matter of timing and species. Now he grows it for forage. I let it mature. Same principle though.

    Profitable grazing based dairy systems.

    Sustainable 12 Aprils Dairy Grazing

    How much grain that is a net CO2 emissions source is grown to feed confinement dairies and feedlots? How much would it change the net balance if all of them were converted to either pasture cropping of even just grazing?

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  10. RedBaron @9, the only relevant section of your first link I can find states:

    "Well-managed grazing systems can cause dramatic improvements to soil quality from organic matter or soil carbon accumulation. This contrasts with row crops, especially such crops as corn silage that return little in the way of root or aboveground biomass to the soil. In the southeastern United States, converting tilled cropland back to grassland increased soil carbon about 3.5 percent per year for up to 40 years until a higher soil carbon stability level was reached (Conant et al. 2000). Owens and Hothem (2000) found higher levels of soil carbon in pastures than in no-till cropland on the same soil types after 20 years."

    There is no indication that I can see that pastures are no-till seeded with grains for cropping while continuing to be used as pastures in other seasons.  The paper cited regarding soil carbon for no-till cropping of corn (Owens and Hothem 2000) shows a decline of soil carbon content of 300 tonnes per km^3 over ten years from the base condition.  That is hardly convincing support for your case that soil carbon can be increased by pasture cropping of corn.  Indeed, it is no support as it does not discuss the case at all.

    For your second link, I could not find the link to the video itself, but the pdf of the planting and grazing guide shows the corn is planted to be grazed, not harvested.  From the "manual", it states that it is planted in rotation with alfalfa (lucerne), a C3 plant.  However, growing lucerne does not increase soil organic carbon in the same way that growing grass does.  Therefore I stand by my claim.  The no-till pasture cropping of grass and a grain will not work with corn; and it is only for the grass/grain case that you have evidence of significant increase in soil organic carbon.

    Further, even if I was wrong on that point, I included land given over to corn and other C4 cereals in my estimate above, so at worst, if I am wrong about the grain, my conclusion stands.

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  11. You are dividing each into individual parts. I am using examples. I don't claim it is needed to only do 1 crop. But agriculture in general is easily large enough. For example plugging in arable land that number above would sequester 256 Gt CO2, grasslands even much more, because the land area is much larger. Our output of 29 gigatons of CO2 is tiny compared to the 750 gigatons moving through the carbon cycle each year, it adds up because the land and ocean cannot absorb all of the extra CO2. About 40% of this additional CO2 is absorbed. About 40% of the land surface is in agriculture of some form or another, including nearly all the prime bits. Change the agricultural models to those that sequester carbon instead of a net carbon emissions source and we do both, reduce emissions, and drawdown what is already there. It is by far and away the largest proposed solution going right now at our current technology far.

    But one would need to be very very serious about this. No fiddle farting around with only changing this or that. It would need to be done world wide. Completely change agriculture to regenerative systems, and even some wild ecosystem recovery projects as well. 

    But the scale most certainly is large enough, especially with what is already being done with solar etc... to reduce emissions.

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  12. doi:10.1038/nature17174 indicates 8 Pg CO2 eq./yr soil sequestration is possible as compared to global anthro CO2 emission of 35Pg/yr . That last figure does not include noncondensing GHG other than CO2, while the first does.
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  13. Let's hope that economic growth can't continue, as it has already done enormous damage to our biosphere. I suspect that it's not compatible with significant reductions in GHGs, globally. I actually can't imagine that it is.

    SRM would remove 2% of the sunlight from reaching the surface. I wonder if that would have adverse consequences, as there are many species, some of which (all of which?) we rely on, which depend on that light reaching them.

    Apparently, it's thought that 450 ppm CO2e is the limit to ensure 2C isn't breached. Last I heard, we were at 480 ppm CO2e. What kind of SRM is required to ensure that, when GHG emissions cease (as they must), temperature doesn't rise beyond 2C? Presumably we would need at least as much as already happens (and maintain it for as long as the shorter lived GHGs remain), along with extra to counteract the continuing warming effect of the unmasked CO2e.

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  14. I wonder why carbon capture by biochar is not given more love by the climate activist.  It is a technology that is ready.  Every wood fire for heat could be burned in a wood stove that is designed to create biochar, with the heating of the building the secondary use of the heat.  Doing so would reduce the heat one could be obtained by burning the carbon also.  However, the biochar has an economic benifit when added to soil (recarbonizing the soil).  This needs to become a global movement to recarbonize our soils.  The worse the soil, the greater the benefit.  Developed countries need to provide support for developing countries to do this.  I am looking for the recognition that we are on the same boat. COP21 conference did recongize this.  We will sink or float as a world community.  Developing good practices for creating biochar can be a world wide jobs program.  Creating biochar from organic material does not sequester carbon.  The plants do that.  What it does is capture the carbon so the plants at the end of their life cycle or more rapidly by burning with no carbon capture (typical) do not emmit the sequestered co2 back into the atmosphere.  

    Agriculture methods of churning up the soil has the advantatge of speeding biological activity by increasing surface area available to air.  However, it also accelerates co2 and other nutrient emissions which depletes the soil.  Therefore, holding onto nutrients would be of greater advantage.  Bio char has proven effective  at doing this by the Pre-Columbian Ammazonian cultures that created highly productive black soils in the normally poor soils of the rain forest.  That carbon is still sequestered millenia later.  IT IS A PROVEN TECHNOLOGY.  

    Please shine more light on the potential of creating biochar to recarbonize the soil that has a short term economic benefit in addition to the long term goal of achieving a net zero carbon emissions economy as described in the COP21 conference.  

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  15. @ ELIofVA #14,

     You wonder why carbon capture by biochar is not given more love by the climate activist? It's simple actually. The one industry even more taboo to mess with besides the fossil fuel industry is industrialized agriculture. Both need radical changes to be sure, but try arguing that and you will meet with massive opposition and obfuscation.

    So basically those of us who are concerned about and working to develop carbon mitigation strategies are facing massive pushback. In some cases even from climate scientists. In the case of agricultural mitigation strategies there even is an unholy alliance between climate scientists and denialists, even ecologists in some cases. I could even give you examples from this website, but not willing to upset the apple cart too much. I still need the ability to post here. Don't want to lose that priviledge. This way at least I can post scientific studies and reviews from the minority opinion as they get published and I find them.

    Just keep plugging though. Soon enough opinions will be forced to change. Agriculture will be forced to change even sooner than the fossil fuel economies due to soil degradation worldwide. Since the solution to both is carbon in the soil, one way or another it will happen.

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    Moderator Response:

    [DB] Inflammatory snipped. 

    Please note that posting comments here at SkS is a privilege, not a right.  This privilege can be rescinded if the posting individual treats adherence to the Comments Policy as optional, rather than the mandatory condition of participating in this online forum.

    Please take the time to review the policy and ensure future comments are in full compliance with it.  Thanks for your understanding and compliance in this matter.

  16. ELIofVA @14, as of 2012, the total global production of plantation timber was 520 x 10^6 m^3 (download of PDF of report 3MB), or approximately 260 x 10^6 tonnes of wood.  That wood in turn contained about 130 x 10^6 tonnes of carbon.  In the same year, total human emissions amounted to 10.5 x 10^9 tonnes of Carbon.  That is, if the world's entire production of plantation wood was turned to charcoal, and buried, you would sequester just 1.2% of the total annual anthropogenic emmissions.  Inother words, biochar can at most provide one strategy among many to tackling climate change, and a relatively minor one.

     One concern I have about sequestering carbon as biochar is that it is not permanent storage.  Specifically, carbon in soil decomposes, releasing CO2 into the atmosphere.  That decomposition may, or may not be temperature sensitive, but it certainly exists.  The consequence is that there is an upper limit on the improvement of soil organic carbon by improved agricultural methods, which will vary by location, type of soil, drainage, and other factors.  That does not mean such methods are not a good strategy for reducing CO2 content in the atmosphere, but they will not permanently offset CO2 emissions.  (They will also need to be sustained more or less permanently a significant fraction of the increased soil organic carbon content will be returned to the atmosphere as CO2.)  Biochar is said to be resistant to this type of decomposition, but it will not be immune to it.  In the limit, biochar will decompose until its contribution to soil carbon does not exceed the equilibrium value of soil organic carbon in any particular environment.  That will probably take thousands of years.  The effect of that decomposition, however, will be a reduced reduction in atmospheric CO2 from the natural take up of carbon once we reach zero net emissions, which in term increases the long term stable temperature increase we can expect from current CO2 emissions.

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  17. Tom,

     "The effect of that decomposition, however, will be a reduced reduction in atmospheric CO2 from the natural take up of carbon once we reach zero net emissions, which in term increases the long term stable temperature increase we can expect from current CO2 emissions."


    Citation needed. Please make it a good one too, no magical thinking citations please.

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    Moderator Response:

    [DB] Inflammatory snipped.  Keep it clean.

  18. RedBaron @17, I have provided two citations for the decomposition of soil carbon to atmospheric CO2 already.  Many more are easilly found by a search on google scholar.  That decomposition will result in an increase in atmospheric CO2 levels relative to what they would be absent the decomposition.  No further citation is needed.

    Your request for a citation is nothing more than a tactic to avoid reasonable discussion of soil organic carbon.  It is on a par with your deliberate, and libelous misrepresentation of the discussion of the subject @15 (since deleted by the moderators).  It is also an evasion of the primary point, the very limited capacity of biochar by itself as a tactic against global warming.

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  19. Tom,

    While it may be true that biochar has limited use, again Citation needed for this quote:

     "The effect of that decomposition, however, will be a reduced reduction in atmospheric CO2 from the natural take up of carbon once we reach zero net emissions, which in term increases the long term stable temperature increase we can expect from current CO2 emissions."

    Keep in mind you are talking about the stable soil carbon fraction, not the active fraction, nor the biomass. I have yet to see anyone at all except you claim that increasing the soil stable carbon will somehow increase the long term stable temperature under any circumstances at all. Firthermore your hypothesis it is so backwards from how the soil and even the entire biosphere actually functions, please provide good citations.

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  20. Global Accounting methods exist for a reason: to prevent Anarchy in the market place.

    Global Warming is a mixed markets failure that is purely down to the worlds Governed markets picking fossil fuels as the winner!

    Extraction of said intervention into the fabled free-marketplace was never going to be easy and any year 11 economics high school student could tell you that. There is a lot of vested interests in messing with the numbers here and if the educated taxpayer that supports it all gets wind of a ruse it's anarchy full stop!

    If biochar and soil sequestration can't be reliably quantified then they can't be reliably quantified.

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  21. RedBaron @19, the citation for that quote is

    I am unsure why you need it.

    Perhaps you meant a citation for the claim made within the quote.  The contentious part of the quote, however follows from two simple syllogisms:

    1)  Biochar decays to CO2 and other decay products over time;

    2)  CO2 from biochar decay is emitted to the atmosphere;

    3)  Therefore, over time, ceterus paribus atmospheric CO2 will increase overtime as the result of biochar.


    1)  CO2 is a greenhouse gas;

    2) Increasing greenhouse gases increases the total greenhouse effect;

    3) Therefore, ceterus paribus, increasing CO2 will increase Global Mean Surface Temperature Overtime.

    Now admitedly I allowed for all not being equal, specifically the natural draw down of CO2 if net anthropogenic emissions are reduced to zero, so that the temperature increase is only relative to what it would have been with the draw down from an equivalent initial peak CO2 level achieved by a more rapid transition of the energy economy, and no use of biochar.  That, however, does not change the logic of the case.

    No citation is needed for the conclusion of a syllogism, no matter how obdurate is the person with whom you discuss the issue.

    So, unless you are claiming that biochar does not decay, simpliciter, (in which case see this, this, this, and and this) your request for a citation is bizarre.  If that is what you are requesting a citation for, you should have actually quoted my claim to that effect.

    But, I remain convinced that your request of a citation is just the response of somebody who has not coherent response to my points; but has to post something to disguise that fact.

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  22. sidd @12, thanks for the presumably interesting reference.  I say presumably because it is behind a paywall and for some odd reason, Nature won't accept my money to let me get beyond it.  I have, however, found an interesting Scientific American article on the Nature article.  The key quote is:

    "The study says that if all the Earth’s farmers were to manage their fields so the soil stored more carbon, the impacts of the greenhouse gases emitted from burning fossil fuels annually could be cut by between half and 80 percent.

    More realistically, the emissions reductions would likely be much lower, possibly between 10 and 20 percent of total annual human emissions.
    “The question of what the most ‘realistic’ potential is, is not really possible to answer directly, at

    least from a science perspective, because it really depends on enactment of policies that would encourage adoption of the climate-smart soil management practices,” study lead author Keith Paustian, a soil ecologist at Colorado State University, said."

    The figures you cite (22.9%) presumably come from the discussion of the "more realistic" figures, which therefore comes with the important qualification that what counts as realistic depends on the policies actually adopted.  The Scientific American article does show that the various news releases that only report the 80% figure are overegging the study, indicating the upper limit of a scenario that is not considered realistic.

    One question I have is, does the paper discuss the effect of the decomposition of the Soil Organic Carbon overtime, and in particular the total amount sequesterable under equilibrium conditions for the farm management practises dicussed?

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  23. Tom @ 21,

     Any further decomposition of biochar after sequestered in the soil, although very slow, would be carbon sequestered from the atmosphere via photosynthesis in the first place, thus rendering it at worst carbon neutral and in no way "increases the long term stable temperature", but rather contributes to long term stable temperature decreases. Agreed it is not large enough to actually decrease temps on it's own, but in no way does it contribute to increased temps, now or in the future. That carbon came from the atmosphere and at the very worst in some extremely long distant view it could be considered carbon neutral once it eventually in thousands of years decomposed completely. Assuming worst case scenario of no transfer to another long term sink besides the atmosphere. The natural cycle adds and removes CO2 to keep a balance; fossil fuels add extra CO2 without removing any. For this reason natural cycles do not add to AGW, but burning fossil fuels does. Also for this exact same reason, since the biochar is sequestered long term, it reduces atmospheric CO2 long term and helps make up part of that lost balance. So for a third time I will ask for a citation. Otherwise just admit your logic was flawed, you made the same mistake climate deniers often make but in reverse  (see denier argument #33 and rebuttal from this website), and we move on.

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  24. RedBaron @21:

    "Any further decomposition of biochar after sequestered in the soil, although very slow, would be carbon sequestered"

    Yes (obviously), but when sequestering the full carbon content sequestered is accounted for as coming out of the atmosphere.  When figures are quoted for carbon sequestration by biochar, the amount cited is the amount buried at the time of first burial.  Not the amount still in the ground after 100, or 1000 years.  Therefore any decomposition must be accounted for as new emission to balance the books.  And unfortunately it is a new emission that is hard to account for and easy to falsely pass of as a natural emission. 

    The result is that people who do not explicitly acknowledge the decomposition (or in most cases even know of it) might think that two pathways, one in which emissions are reduced by 400 GtC by replacing fossil fuel with renewables and one in which 400 GtC is buried as Soil Organic Carbon, and the fossil fuel emissions not reduced, are equally valid responses to climate change.  But they are not, first because the Soil Organic Carbon burial would need to be ongoing, but also because some of that carbon in the Soil Organic Carbon will make its way back into the atmosphere, and over the long term, most of it will.

    That means the role of burial of carbon by improved farming practises represents a good way to buffer the response to global warming.  It allows us to slightly overshoot emission targets to remain below 2 C and recover the difference by sequestration through farming practices.  But it can never be a substitute for reducing emissions to zero in the long term (or indeed, within the next 50 years).  And, what is more, it is a buffer which comes at a cost.  For increased SOC by improved farming practises, that cost is the need to maintain those practises in the long term to retain the equilibrium of SOC.  If for economic reasons we drop those practises in the future, the extra carbon buried will quite rapidly return to the atmosphere (on the order of a century or two).  Biochar, though more limited in the rate at which it can bury carbon, is far more stable so that the rate of return to the atmosphere can take from thousands to tens of thousands of years.  For low levels of biochar, the impact of that will be negligible, but for very high levels it is not.  That means we would need to either commit to long term burial of biochar at a rate to compensate for the decomposition (or other means of sequestration), or not have as great a reduction in temperature as a result of the natural drawdown of CO2 into the ocean.

    Note further that similar problems beset other forms of sequestration.  Even for deep burial in geological strata, there will be leaks so that some indeterminate percentage will be returned to the atmosphere over time.  Indeed, with that method there is the possibility of catastrophic failure of a reservoir and a rapid short term release of some of the CO2 sequestered.  Consequently I think that methods of sequestration by improved farming practise are preferable to the use of biochar, which is much preferable to more industrial means of sequestration.  But none of them can be a substitute to converting to an emissions free energy and transport system. 

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  25. Tom,

     That is a far more reasonable explanation. I would agree that there is no substitute for carbon zero energy long term. But I don't believe that really is the point of carbon farming either. I see the point being to remove the excess already in the atmosphere, not as an excuse to ignore alternatives to fossil fuels. Without alternative energy sources long term, obviously there will reach a time when there really isn't any way we know of to remove that extra CO2. 

    On the other hand even with zero emissions tomorrow, AGW lasts for a very long time. We simply have to help with drawdown, and it's a good thing too, because the soils need that carbon. In my opinion the loss of soil carbon caused by poor agricultural management is an even more pressing issue, with even more catestrophic potential than extra carbon in the atmosphere. Since the solution to both includes moving some of that carbon already emitted by fossil fuels to the soil. I see any accounting defenciencies that you mentioned as a failure of accounting systems, not a failure of the principle of carbon farming in it's many forms.

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  26. Tom Curtis wrote about biochar:

    But it can never be a substitute for reducing emissions to zero in the long term.

    I totally agree with this statement.  I would not suggest that an agressive practice of carbon storage by biochar or any other method would be a substitute for reducing emissions.  One of the risk of optimism on geo engineering is for the public to believe we do not need reduce our high emissions lifestyle because a technological fix is coming. ak "Clean Coal Techonology".  Therefore, biochar is not a substitue for agressive reductions in anthropogenic emissions.  However, when we achieve net zero anthropogenic emissions, (I like to be hopeful) we will still be faced with a carbon concentration that are still too high, causing positive feedbacks such as reduce sea ice (higher light to heat absorption), and release of methane from permafrost thawing.  Therefore, warming will continue.  We must consider how we are going to sequester and store carbon out of the atmosphere.  

    I will use the metaphor of a retention pond used to mitigate the threat of flooding in an urban environment.  A retention pond has an opening for the discharge or rain water.  However, the size of the opening is limited so that during an extreme hard rain, or more frequently when the urban environment has created a very low absorption of run off, the opening reaches a maximum it will discharge and the level of the pond will rise above the level of discharge.  Limiting the discharge of water allows the drainage systems below time to remove the water within the their limits and avoid flooding.  Eventually, all the water is discharged, but at a rate that can be managed.  

    So, when we look at carbon capture and storage technologies, we must acknowledge that they may not be absolutely permanent.  The planting of trees is promoted as a method of sequestering carbon.  Yet a tree has a life cycle in which it will die and decompose the co2 back into the atmosphere.  However, like the retention pond, the process has temporarily removed carbon, allowing time to reduce anthropogenic emissions.  

    Using biochar to more permanantly store the carbon from those trees allows much more time.  The Terra Pretta soils of the Amazon demonstrates that the time frame is in the thousands of years. The release of carbon is very slow.  Better yet, the environment created is a benifit for micro organisms, micro nutrients, and water retention, improving our potential to produce food in a sustainable way for our hungry population.  Therefore there is an ecomomic and local environmental benefit that provides incentive for the process that does not require the achievment of global net zero carbon emissions.  

    From the book, "The Biochar Solution" page 76 the author quotes the belief by Rattan Sal, a soil scientist from Ohio State University that best practices could reduce atmoshperic carbon by 1ppm/4 years.  Currently we are increasing by 2ppm/year.  Obviously, the best methods do not compensate for current emission practices.  Best practices includes other methods beside biochar such as no till farming.  Sorry that I do not have a link to that information.  However, I found this lecture by Rattan Sal that discusses the potential for capturing carbon as a mitigation strategy for climate change.

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  27. Good interview here with Professor Kevin Anderson about COP21 and the task ahead, he's not very complimemtary but always polite.

    Also an interesting lecture he gives at the LSE 

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  28. Suggested supplementary reading...

    From Carbon Brief's daily broadcast email of Apr 11, 2016:

    Explainer: 10 ways 'negative emissions' could slow climate change

    Starting today (04/11/16), Carbon Brief is running a week-long series of articles looking at "negative emissions" technologies (NETs). With the Paris Agreement calling on the world to keep global surface temperatures "well below 2C", compared to the pre-industrial era, most of the climate modelling to date shows that we will have to, in part, rely on NETs in the second half of the century to "suck" CO2 out of the atmosphere. The problem is there are a range of NETs to choose from - yet none have been demonstrated to work at a commercial scale. In this first article in the series, we explain the 10 technologies most often put forward as a way to remove CO2 from the atmosphere. Tomorrow, we ask a wide range of scientists and policy experts for their views. Carbon Brief Staff, Carbon Brief

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  29. John,

    Well at least it made it's way from completely ignored to number 10. I'll take even that as a start.

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  30. While I have been mostly talking about carbon sequestration via the LCP, (a much more stable carbon cycle than biomass sequestration) biochar and the LCP are not necessarily incompatable. Turns out biochar can be an important jump start for the LCP in highly degraded agricultural ground.

    Technical Brief: The Liquid Carbon Pathway

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  31. We know less about the Earth's ecosystems, including soils, than we think we do. For example...

    Researchers are only beginning to understand the complexities of the microbes in the earth’s soil and the role they play in fostering healthy ecosystems. Now, climate change is threatening to disrupt these microbes and the key functions they provide.

    Is Climate Change Putting World's Microbiomes at Risk? by Jim Robbins, Yale Environment 360, Mar 28, 2016

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  32. Further reading on the LCP.

    Humified carbon differs physically, chemically and biologically from the labile pool of organic carbon that
    typically forms near the soil surface. Labile organic carbon arises principally from biomass inputs (such as
    crop residues) which are readily decomposed. Conversely, most humified carbon derives from direct
    exudation or transfer of soluble carbon from plant roots to mycorrhizal fungi and other symbiotic or
    associative microflora. Humus can form relatively deep in the soil profile, provided plants are managed in
    ways to encourage vigorous roots [1]


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