Hello all. I've just discovered this group and its companion (climateintervention) and have spent a happy hour digging through the archives. I'd like to first present a perspective on overall climate- change strategy, and then move directly to the specific issue which is my focus.
First, I'd simply like to put a name to a climate policy position that the world could have adopted. I call it the Triple-A strategy, of Aerosols, Air Capture, and Adaptation. After the subprime experience, dubbing something "AAA" may not seem the best marketing, but they do all start with "A". The reason why I think this strategy might have been optimal is that I expect cheap air capture to be possible long before any program of emissions reductions could make a difference to the world's overall welfare. (The historical imminence of cheap air capture technology is a theme I'll take up below.) And aerosol geoengineering seems to be the only thing we could do right away that would make a change to global temperature in the short term. As for adaptation, I assume I don't need to make a general case for planning ahead! So in short, the Triple-A strategy is one where air capture is the long-term solution, aerosols are used in the interim if a bit of cooling right now is deemed necessary, and all other efforts are focused on adaptation, e.g. anticipation of near-future impacts. I imagine that a few people in the geoengineering community have a view somewhat like this. Instead, the world is mostly embarked on the enterprise of coordinating national mitigation strategies through the Copenhagen negotiations, establishing a carbon price, and so forth. I'm not going to say we should dump Copenhagen and take up Triple-A, but I am interested in exploring the continuum of possible policies between the two approaches, opportunities for air capture to enter the emerging global system (e.g. as a recognized form of offset, as an adjunct to capture-at-source research like CCS, as an adjunct to biosequestration), and so forth. However, since this is an engineering list, and since the political viability of air capture as climate policy is mostly going to depend on its technical and economic viability, let me move on to the more technological discussion. I made a claim above about the historical imminence of cheap air capture technology. By imminent, I meant within a few decades. The real inspiration for this view comes from the "mechanosynthetic" school of nanotechnology associated with Eric Drexler. The idea is to combine the atomically precise positioning of submolecular reactants which can be achieved with atomic-force microscopy, with the atomically precise assembly of molecular components achieved by biological systems. (This description is not quite true to the historical origins of the idea, but I believe it conveys something of how mechanosynthesis is supposed to work.) One may find simulations of nanomechanical components, typically made of diamond and/or carbon nanotubes, which establish something of what their properties would be, without demonstrating that such structures can actually be synthesized. There is also a very small research community trying to find actual pathways to the fabrication of such structures. In years past there was some controversy over the very idea (see, for example, debates between Drexler and Nobel laureate Richard Smalley), but the debate seems to have died down. The existing situation is that "nanotechnology" refers to a very broad spectrum of applied chemistry, and the minority who want to pursue mechanosynthesis, specifically, are free to do so. (I should say that it's not an either/or situation, and that interest in both mechanosynthesis and self-assembly can coexist in the one researcher.) The thing which really caused problems for Drexler's early collaborators was their forecast that nanotechnology was going to revolutionize everything - medicine, space travel, industry, warfare. Also, this conception of nanotechnology has been popularized in ways that are problematic. I imagine that most people on this list have some familiarity with the pop-culture notion of a nanorobot, that can turn anything into anything else because everything is made of the same thing, atoms. If we consider a biological cell as a real-life nanobot, it can certainly perform remarkable material metamorphoses, but it is still constrained by thermodynamics, dependency on a particular chemical feedstock, and so forth. There has therefore developed a pop-culture critique of the pop-culture vision of nanotechnology, namely that it overlooks these and other limitations, which is a sort of shadow of the more rarefied discussions exemplified by Drexler vs Smalley. I'm saying all this just to set the scene for what follows, and to describe my own thinking. Basically, while cognisant of the ways in which the real world of atoms differs from a set of Lego blocks, I do think that ultimately something like a self-reproducing nanodevice, whose diamond-and-nanotube components are mechanosynthetically assembled in an evacuated interior space, ought to be possible. It is going to be a very complex and advanced technology, relative to where we are right now, but I do not see a law of nature that makes such an entity simply impossible. And yet this is the nanodevice-as-doomsday-machine scenario which Smalley in particular was keen to reject as impossible. I think the most straightforward discussion of how such a device constitutes a doomsday machine may be found under the name of "aerovores", devices which "eat the air" - carbon dioxide, specifically. (Aha, says the reader, the connection to air capture technology comes into view.) If you suppose, hypothetically, a nanodevice which can reproduce itself using only solar power for energy and atmospheric molecules for feedstock, then biological rates of replication will have it extracting *all* the carbon dioxide from the atmosphere very quickly, while also smothering the cooling earth in a layer of indigestible diamond dust. Since I do in fact think this is a technological possibility, I am very concerned (to put it mildly) about the prospect of human survival in a world of advanced nanotechnology. But there is one upside to this belief, and that is that air capture on scales capable of returning the atmosphere to its preindustrial condition no longer looks like it costs trillions of dollars. :-) Just one aerovore can do the trick; but you need to program it to stop reproducing after the appropriate number of generations. And good luck with that! I don't propose to hijack this list in order to discuss what to do about nanotechnology in general; there are other forums for that. But what interests me is whether better, cheaper, faster forms of air capture than those we know about can somewhere be found in the interior of the design space bounded by photosynthetic carbon fixation, mineral carbonate formation, air-scrubbing technology, and the vision of a mechanosynthetic replicator. Ultimately it's all chemistry. Is there something in there which has the ferocious carbon appetite of the hypothesized artificial replicator, but which is both less dangerous and more immediately attainable? That's the question occupying my mind. Thanks for your attention, Mitchell Porter Brisbane, Queensland, Australia --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "geoengineering" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en -~----------~----~----~----~------~----~------~--~---
