forum discussion #12

Cooling the Planet with Geoengineering

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Listen to a story by The World’s Alex Gallafent. Download MP3

Our guest in this Science Forum is economist Scott Barrett of Columbia University’s Earth Institute. Chat with Barrett about the science and politics of geoengineering, the emerging field of science aimed at cooling the planet.

Barrett is an expert on international environmental agreements. He is currently studying the politics and economics of geoengineering. He says countries are more likely to geoengineer climate than reduce their carbon emissions. Read his paper on The Incredible Economics of Geoengineering.
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Barrett is the author of Environment and Statecraft: The Strategy of Environmental Treaty-Making. (Here’s a review of the book.) Barrett also blogs for Yale Global Online.

Bring your own questions and comments for Scott Barrett. He’s here in the forum through April 19th. The conversation is just to the right.

  • Should scientists be allowed to plunge ahead with geoengineering technologies?
  • Who should be held accountable for unforeseen consequences?
  • Could there be a geoengineering arms race between countries?

Some Online Resources on the Topic:

  • Get the basics on geoengineering technologies from these Hack the Planet Safety Cards. Hack the Planet is a new book on the topic by science reporter Eli Kintisch.
  • For more information on geoengineering visit
  • More on geoengineering from Scientific American.
  • Scientists from over 15 countries recently met in California to draft a set of rules for geoengineering experiments. Read more about the Asilomar conference.

The guest has left this discussion, but feel free to leave your thoughts.

Your Comments

  1. Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Scott Barrett

    When you first hear the idea of “geoengineering,” you might think it is crazy. You might think it is reckless. You might wish it were banned.

    You might react differently. You might think it’s a “quick fix” for the climate change problem, and that there is no need to do anything else like reduce emissions.

    If you think about the idea a little longer, you might change your mind.

    I hope you will find the story interesting, and have some good questions and comments.

  2. Nicholas Winter

    I am worried that if one of these experiments, causes a major harvest of crops in the mid-west to fail that food prices throughout the world could go up. Even if its just 10-15% price increase that would mean a lot of people aren’t eating.

    • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Scott Barrett

      Good point. I think it helps to imagine scenarios in which geoengineering might be tried. Under a scenario of “gradual climate change,” in which there are winners and losers, the use of geoengineering would also create winners and losers. This means that the use of geoengineering might stimulate conflict. I think this possibility makes it less likely that geoengineering would be used for this scenario. Another scenario is of “abrupt and catastrophic climate change,” in which there are only losers. In this case, the use of geoengineering seems very likely. Of course, even in this case, the situation you describe is possible. But the alternative might seem even worse, and the losses you note could be reduced over time as the world “adapts” to geoengineering.

  3. Mark

    Issue with geoengineering: Unawareness of the full implications of an action, or series of actions.

    I can see any number of scenarios where a fix is issued to “fix the fix,” ad nauseum.

    Of course, is this any worse than continuing to pump the byproduts of fossil fuel burning into the atmosphere, cosequences be damned, as well as unknown?

    • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Scott Barrett

      Interesting. Geoengineering is an experiment, as is human-induced climate change. We are talking about trying to correct one experiment by using another one. Both involve fundamental uncertainties.

      Research can reduce the uncertainties, but we won’t really know the full consequences until geoengineering is tried, at scale, and sustained for a period of time.

      We have a history of using such fixes. To reduce the damages from acid rain, Sweden added lime to its lakes. This was another Band-Aid. It protected the integrity of the lakes until acid rain emissions were cut.

      By the way, acid rain was partly caused by another fix–increasing the height of smoke stacks to carry local pollution away. So, yes, we often need to “fix the fix.”

  4. Les

    It is disgraceful that you consistently refer to alleged manmade global warming without using the word “alleged.”

    If you want to use your radio show to advocate on behalf of the creation of a carbon credit exchange that benefits nobody but the banks invested in it, then that’s up to you.

    But the least you can do is make it clear to listeners that that is what you are doing.

    Or maybe you honestly don’t understand the difference between journalism and advocacy?

    • Les: You oversimplify what the reporter said—and the issue overall. Gallafent said this: “We’re already conducting a massive, unintentional geogengineering experiment by injecting millions of tons of heat trapping pollution into the atmosphere.”

      “Experiment” implies we can’t be totally sure of the ultimate consequences of greenhouse gas emissions until it is concluded. That said, the physics of greenhouse gases are well known. Based on that objective knowledge (and many other threads of evidence), the overwhelming majority of scientists who work in this field say we run a high risk of warmer temperatures, increased drought, etc. if we do actually follow the experiment to its conclusion. In other words, this is about risk, not certainty. And Gallafent didn’t say anything to the contrary.

      • Les

        Tom Yulsman:

        Thank you for your response.

        800 characters is insufficient to engage in a protracted science-based exchange.

        My major point is that–alluding to the same inherent unknowns that you allude to, and acknowledging the arbitrary computer moodeling required to arrive at the pro-AGW position et al–NPR and any objective news provider, is journalistically dishonest by not modyifing its referrences to alleged AGW with the standard “alleged.”

        Further, the scientific concensus that you refer to is apocryphal, based on the result of decades of skewed data emanating from the IPCC, which is funded by, and consistently serves, the carbon credit exchange funders via the UN.

        Addressing alleged AGW and not the banking impetus behind it is naive and damaging to us all.


    Hello, Mr. Barrett
    I just heard the report and have this opinion & question. I’m under the impression there are already Geoengineering projects well under way. To this day, no one has been able to properly explain to me what CHEMTRAILS are about. Chemtrails have been well-documented for at least a decade.
    I suspect because of the advanced technologies governments ALREADY possess, they are attempting to correct what Man-Made Global Warming we have already caused to our fragile planet. Your thoughts???

    • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Scott Barrett

      Contrails or condensation trails do have effects on the climate. They can trap heat and reflect sunlight, having opposing effects. Overall, the effects are very small. Sulfates emitted from power plants can reflect light, providing some cooling. The emission of black carbon has a substantial warming effect. These emissions also have important health effects. One idea for geoengineering would involve seeding marine clouds with salt water spray, to make them whiter, so reflecting sunlight.

      No government is deliberately trying to modify the climate using any of these approaches. There have been efforts to modify the weather locally.

    • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Scott Barrett

      I’ve been asked why I didn’t respond directly to the question about chemtrails. The reason is simple: I know nothing about them. I’ve never heard of them before, ever, let alone in the context of geoengineering. I limited my reply to the possibly related phenomena I have heard of, both in affecting climate change and in relation to geoengineering.

      • David

        The chemtrails reference is to one of the conspiracy theories that “they” are injecting things into the atmosphere to “do things” to people.

  6. Jen

    If my understanding is correct, simply reducing emissions, if accomplished, would only slow down climate change, not stop it entirely. Geoengineering techniques need to be evaluated on their individual merits rather than dismissing the field altogether. I think we need to be persuing methods of reducing greenhouse gasses in the very least.

    • Jen, it seems well-established that warming will continue for at least decades after emissions are cut, but the goal is to avoid exceeding global average warming of 2 degrees C by the end of the century. Many climatologists view that as a danger point considering thermal inertia and amplifying feedbacks in the climate system. If necessary, we could carefully deploy geo-engineering in the future as necessary, IF there’s a failure to control emissions. A good reason to STUDY certain concepts.

      There are a few interesting methods that could absorb CO2, but they seem woefully inadequate (and at least in one case expensive), even with today’s global inflow rates (approaching 30 billion tons CO2/8 billion tons carbon equivalent annually).

      • Adam

        One method I’ve pondered for geoengineering is carbon sequestration in the Black Sea, mimicking the Azolla event in the Eocene. I’d be interested to hear if anyone else has considered this.

        The Azolla event occured when the Arctic ocean was separated from the other oceans and had an anoxic bottom layer of water, like the Black Sea today. Massive amounts of floating water plants grew on the surface, and sank to the anoxic layer, where they are preserved mostly undecayed to this day. During this time period the earth’s CO2 levels and temperature dropped quite a bit. Dropping a lot of organic material into the Black Sea seems like a cheapish way to sequester a lot of carbon and I’d like to hear what someone with more knowledge has to say about it.

  7. Margie

    Aren’t global corporate influences and practices that have done global damage that need to be reengineered?

  8. Sharon

    Controlling climate change by controlling the weather has too many variables that have not been resolved. We need to prevent pollution problems, which we know how to do, rather than seeking artificial fixes that we are uncertain about. Mirrors in space? Doesn’t that seem unwieldy and costly? Seeding the atmosphere with reflective material? Where will that eventually go? We need more answers. How can controlling climate change be EXPERIMENTED with responsibly? By what government? BTW, I live in Arizona in a place that used to have clear, blue skies. Now, the sky may be blue in the morning, but by afternoon it is milky white or gray from the multitude of jet trails that hang in the air and cover the sky for 12 – 24 hrs. Has anyone studied what that is doing to our weather?

    • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Scott Barrett

      There is no question but that the most conservative policy would be to conserve energy so as not to put more CO2 into the atmosphere.

      I would only add that some of the policies we may take to reduce emissions also entail risks. Nuclear power is an example. If nuclear power spreads to countries that lack experience with this technology, and that have unstable governments, the risks of proliferation will grow. Also, nuclear waste disposal is a very long term problem, a little like the emission of greenhouse gases. It’s another problem we have not solved.

      Our efforts to address this challenge entail risk-risk tradeoffs.

  9. Greg

    This seems a bit of fear mongering. Just as emissions in one country raise the global CO2, any geoengineering strategy would have global not local consequences. The only consequence that matters is reduction in temperature which will affect all & benefit most. The particular means to that end could have local consequenses such as iron seeding the ocean to encourage phytoplankton growth or acid rain from sulphate aerosols. There are sure to be unintended consequences, but all the options need to be considered since we are doing such a lousy job of reducing emissions. When I consider how much is known for how long & how little has been done about global warming, geoengineering seems inevitable if not desirable.

    • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Scott Barrett

      I follow your logic. The incentives to reduce emissions are muted because of this being a collective action problem. Geoengineering is like adaptation. It can be done unilaterally. And the financial cost, as we understand it today, are low. So I think the chances are high that geoengineering will be used someday. Again, the reason for this is that we haven’t addressed the problem fundamentally by reducing emissions. Of course, geoengineering is unlike adaptation in that the entire world would be affected. So this explains why the big problem for geoengineering is governance: who decides whether and under what conditions geoengineering should ever be tried?

      • I think the thing that bothers me the most is related to this post. Geoengineering has the potential to positively or negatively affect every single life form on earth. There is simply too much risk being assigned on people who have absolutely no official say in the matter. I am middle/low income college student in a town with a marginalized economy. If things go bad, I can guess with a reasonable amount of certainty that there will be no substantial reimbursement, or official apology. Worst of all it may very well be funded by my own tax dollars.
        Thanks for starting a very interesting conversation.

    • Bert Vaughan

      Since it required the burning of such collosal quantities of fuels, over so many years, to precipitate this situation, can you let me in on any one of these “options” with might have a sufficiently drastic effect to change matters globally ? I suppose merely re-planting – if that were possible – the destroyed forests of the world would be just “tinkering” to a “Geo-engineer” – whatever one of those might be. Someone with a hugely inflated opinion of themselves I would suggest.

  10. Gabriel

    Please keep re-iterating that reductions in greenhouse gases are the preferable option, we need to get off oil for the coming crunch in supply anyway. We can choose to retool our economies with coal and chain ourselves to another dirty, possibly suicidal, regime, or we can make use of the renewable supplies of energy all around us. BTW, to people saying that climate change should be prefaced with “alleged”… the people who are alleging that it is a threat are NASA, the Department of Defense, NOAA, NSF and every single major scientific organization in the world. Find one major scientific body that represents real post-graduate professional scientists (not dedicated to petroleum extraction) that does not. Bloggers don’t count, which seems to be where the denial camp gets most of their info.

    • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Scott Barrett

      We should certainly reduce global emissions, but we need to do more than that. The problem has advanced so far that reducing emissions may not be enough. We need also to develop new technologies that will allow us to reduce emissions at lower cost in the future. We need to adapt and help vulnerable countries to adapt. We need to develop the capability to remove CO2 directly from the air–the only backstop technology for emission reductions. Finally, we need to contemplate the possible use of geoengineering. As Jen mentioned above, even if emissions were to stop today, the climate would keep changing due to thermal lags. We might still confront a scenario of abrupt and catastrophic climate change.

  11. Ryan T

    It’s foolhardy to pin the future on barely-studied concepts that could carry higher costs than making the effort to cut fossil carbon pollution to below Earth’s sink rate. The geoengineering ideas I’ve seen are not permanent, but processes that need to be sustained to counteract long-term amplification of the greenhouse effect. That means toying with Earth’s energy budget using orbital techniques or chemicals injected into the stratosphere over long periods, with who knows what consequences. It would be an attempt to use a micro-management bandaid (altering insolation over X percent of the Earth’s surface or in one component of the climate system) to deal with a growing macro-level climate influence (fossil CO2 accumulation).

    Some good discussion and links on this:

    • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Scott Barrett

      Yes, it would be foolish to pin our future on geoengineering. As I said in my reply to Gabriel, we need to reduce emissions and do other things as well. I would only add that it might also be foolish to ignore the possibility that we may someday wish to consider using geoengineering. There are scenarios in which not using geoengineering could be worse than using it.

      • Ryan T

        I do agree with this. We need to keep our options open, but some people appear to latch onto geo-engineering as if it’s likely to be a safe, cheap primary fix. That’s still quite a bet to make, but perhaps for some it’s a convenient assumption.

        We do need OPTIONS, but so far I’ve not seen a compelling case for the immediate need to implement more than a carbon control campaign (emission and sink oriented). If we get serious with that, we could at least buy some time to better study other proposals (especially those going beyond incremental restoration of Arctic albedo). Yes, we’ve already embarked on a long global engineering campaign of sorts. Now it seems wise to more carefully consider the ways of restoring some radiative balance. I think I’ll feel that way until I see major science institutions or high-profile climatologists saying the problem has reached a critical phase, requiring negative forcing regardless of what it might do to regional climates or ocean ecology etc.

  12. Jane

    First I’ve heard of it. I’ll have to read up on it. How much will geoengineering make sense if you don’t mandate emissions cuts? (Good luck getting the U.S. and China on board.) We must face facts eventually and stop being a consumer society.

  13. Brad

    I think people are becoming more familiar with the carbon cycle as you seem to be, but you neglect that science clearly and plainly shows humans contribute to CO2 concentration in the atmosphere which is well above what the natural carbon cycle produces – the evidence is much stronger than a simple correlation. The planet does maintain a certain concentration of CO2 in the atmosphere when the system is in balance, but the burning of fossilized hydrocarbons since the industrial revolution has lead to a somewhat exponential increase in atmospheric and this CO2 becomes so dispersed up there that natural recapturing of the gas from the atmosphere cannot maintain the balance and any feats to recapture already emitted gases is simply inconceivable.

  14. Brad

    I think that geoengineering experiments sound scary, but as that author mentioned, we ought to have all of the cards in our hand. A lot of predictions will first have to be made, which means climate modeling, and as we all know from the daily forecast: modeling the climate is complicated and hard to do. But as regional and global temperatures rise, it puts a lot of pressure on less stable ecosystems and sensitive farming regions, and the pressure to react to climate changes will only intensify. Eventually some of the risk would be outweighed by the potential benefits – and if you are a country with a lot of clout you may decide to proceed regardless of what your neighbors have to say. So geoengineering sounds scary if we/they do it, but how scary could it be if no one does it?

  15. As an environmental health scientist, I want to caution the scientific community about proposing various geoengineering fixes without considering possible adverse consequences on human health. Granted, climate change already has negative consequences. A World Health Organization report just published estimates 150,000 deaths per year already because of climate change. We just need to be sure, as much as possible, that any proposed solution will not have unintended consequences for life on earth. Environmental health has two sides: the effect of humanity on the health of the environment, and the effect of the environment on the health of humanity. We need to balance both sides of the equation. Thanks for this informative discussion.

  16. Ken Saunders

    Geoengineering should be studied and tested as a hedge against what seems like the very real possibility that — for whatever reason — the world just doesn’t reduce CO2 emissions enough to stabilize the world’s climates. We (Earth’s inhabitants) just don’t do it, period.

    Of course, I’m assuming that somehow (I actually don’t see how) it can be decided that climate stabilization is what we (again, Earth’s inhabitants) want to do.

    I do think it could be made to work, but the side effects might be worse than the cure.

    • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Scott Barrett

      Humans evolved in association with our climate, and our infrastructure was built to suit today’s climate. Small amounts of climate change can produce winners and losers but larger amounts would very likely trigger substantial losses all around. I think the case for limiting climate change is overwhelming, even if the precise limit is more difficult to pin down. To limit climate change, we can either limit concentrations or try geoengineering. The former approach gets at the problem fundamentally, but would require an unprecedented effort–reducing net emissions towards zero worldwide. The latter approach would be a “quick fix” and, as you say, would likely have unwanted side effects. Probably a combination is needed, perhaps with geoengineering being kept in reserve, to avoid catastrophe.

  17. DJ

    I have a couple of related questions. As atmospheric CO2 increases, it dissolves in water, including the ocean, producing H2C03, which is an acid that acidifies the ocean. Geoengineering seems to treat one symptom of increased atmospheric CO2, not ocean acidification. First, are there ways other than cutting emissions to treat the symptom of ocean acidification? Second, are there other symptoms of increased atmospheric CO2 in addition to ocean acidification and climate change? Thanks!

    • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Scott Barrett

      On your first question, reducing short wave radiation to cool the Earth would not address ocean acidification. It is not a perfect substitute for reducing atmospheric concentrations. A key technology, I think, is the direct removal of CO2 from the air. This technology would allow us to address the problem directly, but it is expensive. I think we’re most likely to use it if things look very bad, and we also dislike the full consequences of geoengineering. On your second question, the only other effect is “fertilization” of plant growth. CO2 is not a pollutant. Other greenhouse gases can have additional effects. For example, some deplete stratospheric ozone (which is itself a greenhouse gas!).

  18. Joan Riggs

    Hi Scott,
    I was in your classes at SAIS. Good to hear you doing such interesting work. The PRI story reminded me about our game theory exercises in class. This is a complex problem, with the divergent incentives.
    Joan Riggs

    • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Scott Barrett

      Dear Joan,

      Great to hear from you! I hope you are very well.

      Yes, this is game theory, being played out before our eyes.

      Best wishes,


  19. Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Elsa Youngsteadt

    Alex’s radio story mentioned several potential geoengineering technologies (mirrors in space, reflective particles, CO2-absorbing artificial trees, etc.) Apart from the ethical and political implications, which technologies are actually most developed and closest to potential testing?

    • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Scott Barrett

      Mirrors in space is the least likely option. It’s technically challenging, expensive, and risky. The artificial trees have already been tested as pilot projects. As I mentioned in an earlier reply, I think this technology has a future, even though it is very expensive. It’s the closest thing we have to a backstop technology for emission reductions. Reflective particles are extremely plausible. Mount Pinatubo showed us that sulfate particles thrown up into the stratosphere can cool the earth in a mater of months (and deplete stratospheric ozone in the bargain). There are lots of other ideas, and we’re only beginning to think about this. My guess is that the technology or technologies we end up developing one day will look different from the ones we’re considering today.

  20. Bruce W.

    Ryan said: “It’s foolhardy to pin the future on barely-studied concepts that could carry higher costs than making the effort to cut fossil carbon pollution to below Earth’s sink rate.”
    That is exactly what humanity has been doing in the 1850-present steam and internal combustion epoch. It has only been in the last 25 years that serious consideration has been given to changing that.
    Now, we need to reverse ill effects on the planet, not just slow them down. For instance, if the polar ice caps are melting, how do we “refreeze” them? Simplistically, a giant air conditioner would seem to be called for.
    We could sit for eons pondering how and what the cost and what side effects. It takes us ages to discuss and disagree and fuss and fume, all the while the situation gets worse.

  21. Amy S.

    Thanks for talking with us, Mr. Barrett. I don’t have a great deal of experience with this issue; my only good education on the subject was a general undergraduate class on climate change. I’m curious how we’ll implement this in a gradual way to observe the effects on human, animal, and plant health. The problem that I see with geoengineering is that once we’ve tried it, it seems like it’ll be a very difficult thing to reverse or alter if we find adverse effects. You could try to, say, release reflective particles in a specific location to allow study but the atmosphere will transport the particles around the planet, like we see in volcanic eruptions. How would that be addressed?

    • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Scott Barrett

      Amy, this is an interesting question. How do we test something like this?

      If we don’t test at all, we won’t know whether it will work or how to make it work better or what its side effects will be. If we do “little tests” we won’t know how it will work at scale. If we do “short term” tests we won’t know its long term consequences. So the distinction between testing and deploying can be blurred. This is one reason why I think we need to develop a governance arrangement for deployment as well as for research.

      Probably the most obvious test would be nature’s own–that is, to be prepared to examine very carefully the effects of volcanic eruptions.

  22. Richard Strauss

    I was quietly resting/dozing when the piece on Geoengineering started. My immediate thought was, a very good April-fools joke. Truly! As I listened I realized it was well past April 1st. Build a machine to do what trees already do for the planet??? Could this be a part of the “Build a Smarter Planet” campaign from IBM? We sure do think the planet must hold Homo sapiens, an experiment, too big to fail.

    Homo sapiens (Latin: “wise man” or “knowing man”). A prime example of a Latin joke?

  23. Richard Firestone

    Geoengineering is a dangerous concept that must be avoided at all costs. It is sheer folly to believe that we will ever understand the Earth’s climate well enough to manipulate it. Too many random, unexpected variables will come into play. We all fear and need to prepare for possible global warming. However the arrow of history clearly points us towards an ice age in the near future whose consequences will be infinitely worse. How do we know whether geoengineering won’t push us more quickly into that ice age. As Fred Hoyle has written, the natural state of Earth is an ice age and this cycle is only broken by periodic extraterrestrial impact events. Hoyle argued that global warming would actually forestall the ice age. Perhaps geoengineers will need to engineer a meteor impact.

  24. Doug J

    Every one of these “solutions” are a proposal to firstly secure a need for someone’s or some group’s expertise, product, or whatever “racket” they have going. Carbon sequestration is a typical case; oil drillers want to do more drilling and get paid for it. They could spend the remainder of their individual working careers being paid to monitor and repair subterranean CO2 feilds; job-security you see.

    Frankly all these folks need first of all to spend 6 months or so every year in the Canadian and Siberian sub-arctic planting trees. Then they should spend a few weeks every year bringing in the harvests, [manual labor, that is]

  25. Steve Jordan

    Engineering has done some wonderful things for people, but also some awful things. Engineering in general is devoted to making things work, not making them right in a broader sense. Two of the most scary proposals for geoengineering are seeding the oceans with iron to stimulate phytoplankton, and pumping sulfates into the atmosphere. The ecological and human consequences of those fixes would likely be worse than climate change. Any such proposals would need the most stringent scientific review. Beware of bright ideas and “common-sense” solutions. They are dangerous.

    • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Scott Barrett

      This is essentially why geoengineering poses a profound challenge to governance. The big question is, Who decides these things? A key thing to remember is that there are lots of countries capable of deploying a geoengineering project.

  26. David

    Do you really think at present, we have a sophisticated enough technology to even begin to approach working on the environment at a global scale?

    Our most powerful devices (atomic weapons) all fired simultaneously are no nowhere near the power of vulcanism.

    The idea of seeding oceans on a global scale would require huge amounts of energy and materials. Could they even be transferred fast enough to avert some ecological disaster? Would the effect of gathering, refining, and moving all the materials create more harm than they would be supposed to solve?

    (P.S: The chemtrails reference is to one of the conspiracy theories that “they” are injecting things into the atmosphere to “do things” to people.)

    • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Scott Barrett

      Engineers say that this can be done. You might see the Royal Society’s report at

      Whether geoengineering could avert a climate catastrophe depends partly on whether we have done any R&D on the technology before its deployment is thought to be needed.

      Might geoengineering cause more harm than good? Yes. This is why the R&D is needed. This is also why a governance arrangement is needed.

      (Thanks for the postscript.)

      • It is possible to do incremental engineering designed to do good. If it turns out bad it can be adjusted progressively. — Please see beta video of our design on You Tube, under pluvinergy. You can see extended argument at, pw: sise. If this process works it removes, CO2, produces water and energy, cools the planet directly. Of course a lot can go wrong. If first design is damaging in some way,next design can adjsut for that etc.

  27. Peter Morgan

    Interesting that you think the environment susceptible to the methods of game theory. Telecomms companies have learned, I think, that when governments (and bidders) use game theory to optimize their income from large-scale bandwidth auctions, the games can become very risky, creating big losers and big winners. Ditto stockmarkets. Unintended and unexpected correlations can bite. Geo-engineering is by definition government scale or larger, which seems to invite significant probabilities of very big losses. To add difficulty, testing, as you say above, merges into deployment, to which I would add that assessing and neutralizing the inertia and vested interests of the players involved in an intervention is nontrivial, complicating the design and implementation of effective exit strategies.

    • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Scott Barrett

      As you say, game theory has been used to design airwaves auctions. Some of these have succeeded spectacularly.

      For readers who are unfamiliar with the technique, game theory is simply the study of interdependent decision making. It’s relevant to climate change because concentrations of greenhouse gases depend on the sum of the emissions of all countries. Every country might be willing to cut emissions, but only if assured that others will cut theirs. It’s for this reason that countries met in Copenhagen last December to negotiate an agreement. Game theory can also help to understand why those negotiations were so difficult and why the end result will make little difference. I use game theory to learn how we could do better.


  28. Nick Turner

    I read your paper and I agree with your view that first and foremost, a protocol should be established to answer the “who decides” question of whether or not and how to implement.
    My question is this–you mention that geoengineering would not affect high carbon dioxide levels, and this would aid agriculture; would the decrease in sunlight penetrating the atmosphere harm agriculture? And if so, would it be enough to do damage? The world is already short enough food.
    Also, What are the potential risks of seeding algae blooms in the ocean?

    • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Scott Barrett


      Yes, the decrease in solar flux would harm agriculture, but one paper suggests that the CO2 fertilization effect would dominate, leading to an increase in net primary productivity. Of course, we also need to worry about other things. There could be regional and ecosystem-specific differences. Also, changes in rainfall will be very important. And higher CO2 levels in the atmosphere would spell greater ocean acidification. So, overall, the effects will be mixed. We need to understand them better.

      The supply of food overall will depend on more than climate change and geoengineering; it will also depend on agricultural R&D and related investments and policies.

    • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Scott Barrett

      The ecosystem risks of “ocean fertilization” are unknown, though blooms do occur naturally. The bigger problem may be the ocean’s limited capacity for CO2 removal (only some areas of the ocean are nutrient-deficient). Another problem is verification of the amounts removed.

      Finally, we should remember that the oceans are being damaged for many other reasons.

  29. Paul Heller

    Efforts to reduce CO2 have little leverage. They are slow and expensive and most importantly require major changes in how most people live and how most businesses operate. This won’t happen voluntarily and few governments could legislate such changes.

    Geoengineering has very high leverage. A poor country or even a rich individual could have noticeable impact on the climate. It seems quite possible that this could be monetized for private benefit through localized changes in wind, precipitation, or even temperature. Where there is the possibility of huge private benefit, it seems likely to happen. With two or three decades of government funded R&D, private interests will probably have several geoengineering opportunities to chose from. I am not optimistic that we can manage this.

  30. J Harmon

    The primary objective for geo-engineering is to simply minimize the cumulative effects of human presence on Earth. If geo-engineering can neutralize the harmful effects of our activity against the climate and its own regulatory processes, without further interfering with those same processes, then the natural climate can prevail. This approach also minimizes the concerns that unbounded geo-engineering would further upset the climate, e.g. due to unwise technological tampering with nature’s normal regulatory mechanisms. Therefore, the other important consideration is to establish a rational foundation for the “Cap and Trade” bills and treaties being considered, since these bills seem to be focusing more on taxation revenues and regulatory rule making vice promoting innovative enterprise.

  31. Rick Fisk

    Why not focus on “geoengineering” at the source point, ie each automobile becomes neutral, not adding or subtracting. These are more easily acheivable goals, incrementally implementable and do not pose the same risks for mis directed concern about global warming, profiteering or politicos.

    • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Scott Barrett

      How to make the car carbon neutral? One way is to change the energy source. For example, moving to the all electric car, with the power being produced by renewable or nuclear energy. Another way may be to remove CO2 from vehicle exhausts (a suggestion put to me by one of my students), but I don’t know if this would be economic compared to the alternative of offsetting vehicle emissions by direct removal of CO2 from the air. There are other options. For example, we could produce synthetic hydrocarbon fuels by producing hydrogen using renewable or nuclear energy and combining this with carbon removed from the air. A major issue as regards all these options is cost, and our willingness to pay the cost.

  32. Adam

    Given the unplanned and often unwise changes we impose on nature as side effects of agriculture and industry, I think it’s odd to try and avoid making planned changes directly to nature. A bit like accidentally installing malware onto a computer when downloading programs for your own use, but then refusing to install and run antivirus programs because that would be “tampering with your computer” and you might damage it.

    I think some type of sequestration is the best and safest way to go. I have a master’s in marine biology, so I worry about ocean acidification. CO2 sequestration addresses the root problem, while reflecting light only helps some symptoms (and seems a good deal less controllable). Of course, some source of cheap, carbon free power would also be an immense help.

    • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Scott Barrett

      These are all good points. The most “conservative” approach is not to put CO2 into the atmosphere in the first place, especially by conserving energy (replacing fossil fuels with nuclear energy would be equally effective in reducing emissions, but increase the risks associated with long term storage of nuclear waste and proliferation). Air capture and sequestration is a more perfect substitute for emission reductions than solar scattering, as you say, but there may be risks to storage–we need to learn more about that. “Solar radiation management” has an advantage over direct CO2 removal–it can change temperature quickly. Also, its financial costs are lower.

    • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Scott Barrett

      I also agree with you that having a source of cheap, carbon free power would be of enormous help. Google has the ambition of developing renewable energy that is cheaper than coal. If they can do this, a big part of the problem is solved. In some settings, renewable energy is already cheaper than coal. The problem is extending this to more and more settings. That won’t be easy for lots of reasons. Even if the efficiency of renewable energy is improved, storage and transmission also needs to be improved. Another thing is that, as renewable energy becomes more competitive with coal, the price of coal will fall, making more people want to burn coal. So this approach is somewhat self-limiting. I can’t see how we can reduce emissions without a carbon price.

    • Bert Vaughan

      But unlike a computer which is entirely a known-about, and finite, object, “Nature” – the weather for instance – in not. And if it were, just what brand of “anti-virus software” should we apply to “Our computer” – The Earth ?
      Your brand ? my brand? his brand, her brand ?
      Their brand ?
      In view of “Man’s ?” attempt at CO2 reduction – “Windfarms” – which are entirely counterproductive, btw, (but they don’t let this slow them down), why should I have faith in one of their even “greater” ideas ?

  33. Adeesh

    As I’ve come to understand geoengineering, it has two parts right? One the soft part and one the hard part (pardon my English please), where soft part will be to improve upon our current emissions and other wastage in terms of air, water etc. And the hard part being actively increasing ozone levels or reflecting back sunlight etc.
    I am a supporter of the soft part of this. It involves eliminating the meddling and might result in the environment itself working back towards it’s suitable equilibrium without us wasting resources trying. But living here in Indore, India, where already temperatures have reached record highs for April, I feel (and I admit I have no empirical reason to) that maybe more harsh measures may be of order because (contd in next post)

  34. Adeesh

    …my reason is that we already know some things about what the climate was like when the weather was two degrees colder. So if we can decrease the weather by two degrees, we should expect a more favorable climate minus the harsh consequences that are predicted right?

    I’d also like to ask you, what sources online are reliable sources concerning data on global warming. Is a good website to rely on?

    • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Scott Barrett

      Dear Adeesh,

      This is how I see things: Climate change is a risk. To limit the risk, we need to reduce reduce emissions; we need to develop new technologies that will allow us to reduce emissions more cheaply in the future; we need to adapt and to help vulnerable countries to adapt; we need to develop technologies that can remove CO2 directly from the air; and we need to contemplate using “geoengineering” to offset the effect or rising atmospheric concentrations by deflecting sunlight. As the problem is that atmospheric concentrations are getting too high, we need to limit this level. Other approaches are ways of limiting risk until we can do this.

    • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Scott Barrett

      As for online sources, I don’t know the web page you mention. Other people may have views about this or other suggestions.

      The IPCC offers the “consensus” view, which has strengths and weaknesses but is an important source:

      I rely on original sources, and read the journals Science and Nature (among others) which publish original, peer-reviewed articles and include summaries written for a general audience. Nature has a special section devoted to climate:

      I am an advisor to Earth & Sky, a radio program in the U.S., and like their work because they speak directly to scientists:

      You can’t find enough sources for this issue. Again, other readers may have other suggestions.

  35. Hi Scott – thanks for taking part in the Forum. You mention the benefit of being ready to measure the effects of volcanic eruptions (since such eruptions may model the effects of certain geoengineering techniques.) Just curious: do you know if anyone’s measuring the current eruption on Iceland?

    • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Scott Barrett

      Hi Alex,
      Thanks for the great story. I had thought of the same thing. I don’t know if this volcano is being studied with this purpose in mind, but it is a “natural experiment” that deserves our attention. Of course, geoengineering would be different. It would rely on particles designed for the purpose, and injected in a place intended to have the desired effect. But obviously we should learn what we can from this experience before considering “field experiments” of our own.

  36. Tim McGuire

    As I listened to the guest speaker yesterday–driving along in my SUV–he described the need for a device that could be created to pull carbon from the air and sequester it in the earth…

    I screamed: IT’S CALLED A TREE!

    Carbon-Dioxide in…
    Oxygen out… (BONUS)
    Carbon sequestered in the tree’s structure!

    Plant trees everywhere, now!

    • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Scott Barrett

      We should be doing lots of things, including tree planting. As you probably know, trees eat CO2 when they grow, but they emit CO2 when they decay or are burned. So there’s a limit to what tree planting can achieve. Unfortunately, there are no silver bullets for this particular problem. We have to do lots of things.

  37. Nancy Yuen

    I’ve been reading these posts from the last few days and see that it is primarily about a large-scale “manipulation” of climate, if such a thing can be engineered. Have people lost interest in managing emissions on a local level, ie, not using airplanes to fly everywhere for fun, or driving downtown on the freeway instead of being limited by public transit?
    I feel like this question may be missing the point. I think the only real way to affect the climate on a global scale, if at all possible, is for governments to sign a new treaty that reduces emissions on a relative and/or absolute. Granted, this won’t fix the atmosphere, but at least there is less harm done in the meantime. How do we convince the good people of the developed (industrial?) nations to ride the CNG bus and not drive?

    • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Scott Barrett

      Exactly. We’d be much better off collectively if emissions were cut very substantially, but the incentive countries have to cut their emissions individually are weak. A new treaty is needed to change these incentives, but obviously countries have been unable to figure out how to negotiate such an agreement. Improving on this situation has to be our priority.

      But even if countries were able to negotiate a remarkable treaty today, the risk of catastrophic climate change would remain. This is why we need to contemplate the possible deployment of geoengineering.

      • Error: Unable to create directory /home/worldsci/public_html//wp-content/uploads/2014/04. Is its parent directory writable by the server? Scott Barrett

        I’m writing this last note to thank everyone for their comments and questions. I hope you found the discussion illuminating.

        Addressing climate change is one of the great challenges of this generation. Whatever your views may be about geoengineering, I hope you will continue to stay engaged. A lot is at stake.

        Best wishes to you all, Scott

  38. Mike Pedersen

    I heard in the report, geo-engineering referred to as “desperate measures”, and for this purpose I believe we have to be open to all ideas. The distinct possibility exists that we, as humans, have already been too slow in responding to climate change. We still have a huge uphill battle and human nature is a difficult nut to crack.The reality is that we all need to learn to live with less: less energy, less entertainment and travel, less consumer goods and electronics. I’m still hearing comments in regards to climate change such as, “perhaps in a hundred years or so it will be a concern”. A concern?
    What will this concern look like? Inundated coastal cities, wildfires and drought, an inability to grow nourishing crops in a high CO2 environment? We may yet need “desperate measures.

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