Mike, Andrew (cc List)
1. Thanks for continuing this dialog. The part I find most encouraging in the last several messages (below) is Andrew's statement in his last paragraph re "Bright Water": "..... It's the most exciting new geoeng idea for a long time......". The next most encouraging thing is that every one seems to agree that a lot more exploratory R&D is needed. No-one is urging immediate deployment. I don't see much discussion on the costs and the urgency . 2. I have just started reading some of the many dozens of the technical references that Russell has provided. Besides being impressed by that number, I am impressed by the depth of past work on bubbles and especially ocean bubbles. This is a field with a substantial, credible and continuing literature - both theoretical and experimental- albeit not for albedo modification. We will not be starting at ground zero to answer the good questions being raised about "Bright Water". 3. Three other so far unstated aspects of starting R&D soon: First, almost everyone reading this could find a place to do something useful at moderate cost on this technology. A square meter is probably mot enough, but no-one needs a hectare. Second, we don't need to cover the whole globe to have a sizeable effect in the location most urgently needing attention - the Arctic. A "Bright Water" covering in the Arctic will have a profoundly different impact than the same covered area near the equator. Lastly, if we concentrate on the Arctic (being the most likely place to see a tipping point soon), we only need to cover the open-water (which is not much at this time of the year), and we need only be concerned for the summer months. As Dr. McCracken points out , this perhaps can be coupled with summertime cloud formation in the Arctic - not worldwide (providing further analysis deems that a worthy gamble in the Arctic). If it works out, the next logical location is probably the Antarctic. 4. If we were in a proper "war-time" mood, any developed country could probably get an answer in a year about proceeding to a first full scale effort. Maybe at worse, two years. But we are not in such a mood. The only hope I can see is that one of the few countries with a significant annual budget surplus (China?. Brazil? Norway?) can jump in. I have zero hope for the USA doing anything in the next few years. However, one enlightened billionaire might hear about how small the dollar need is right now - for the only SRM approach I see that can give us the needed (Arctic) breathing room. I am not saying "Bright Water" is a sure bet. Only that I agree with Andrew: ". . It's the most exciting new geoeng idea for a long time......". Thanks to Andrew and Mike for keeping this important dialog alive. If the Arctic ice loss solution is not "Bright Water", what is? Ron Begin forwarded message: From: Mike MacCracken < [email protected] > Date: April 16, 2011 8:37:24 PM MDT To: Geoengineering < [email protected] > Cc: "Russell Seitz (2)" < [email protected] > Subject: Re: [geo] Re: for Geoe E group Bright Water the movie Reply-To: [email protected] Hi Andrew—On your objection about the biology of bright water, I’d like to better understand your concern. How do you think the effect of the bubbles on a clear day would compare to the effects of a thick cloud cover? Countering a pretty significant increase in CO2 warming would require, if it could be done, only a several percent increase in cloud cover [our roughly 50% cloud cover contributes to reflection of 25% of solar radiation; if what we need to do is get a 1.8% reduction in the solar constant where we have a 30% albedo, which is the same as reducing absorbed radiation by about 4 W/m2, then what we need is the equivalent of an increase in cloud cover from 50% to a bit less than 53%, or something like that]. Are you suggesting that an increase in cloud cover from 50 to 53% would have a devastating effect on marine ecosystems? Let me try the calculation another rough, idealized way: If the 50% of clear sky is responsible for increasing the global albedo from 25% to 30%, then, allowing for say 10% atmospheric absorption of solar radiation going each way (forget compounding effect), and two-thirds of this takes place over the 1/3 of area that is land and ice (so average albedo of land is 4 times that of ocean), then average ocean albedo is 6%. To then increase the global average outgoing solar radiation, I calculate that the average ocean albedo has to go from about 6% to a bit over 10%, which would reduce the available radiation in the water from 94% to 90% of incoming solar radiation (accounting only for the effect in clear sky region). While I realize that BrightWater envisions making the albedo a good bit higher, this would mean that I would need to do less elsewhere. Given there are large areas of the ocean where there is little biological activity due to low nutrient levels, perhaps I could concentrate the water brightening in those areas. So, let’s hypothesize that I aim to raise the ocean albedo from 6% to 15% over the half of the ocean area with the lowest biological activity (and I think the low biological activity areas are larger than the marine stratus areas so the pattern of flux change would be less sharp than for the Salter-Latham approach that can get a global counter-balancing. With bubble lives limited, unlikely it would be a problem of bubbles drifting into biologically active areas. Now, let’s think about combining the BrightWater and the Salter-Latham approaches, giving us more even coverage—with the boats shooting up sea salt sprays when below marine stratus and injecting bubbles when in clear skies, so maybe half of the albedo effect proposed is needed by each approach. So, maybe the amount of solar reaching the ocean goes down a couple of percent. Are you really suggesting that this would devastate marine ecosystems—and indeed be worse than reflecting a similar amount of radiation using a global stratospheric aerosol layer? It is true that the combined approaches would be concentrating their influence over the oceans as opposed to the global stratospheric layer that spreads the effect over the globe, but the sulfate aerosols are such inefficient backscatterers that one ends up with a quite high proportion of forward scattered radiation. I am not saying there will not be effects—we’ll need a good bit of research to get a sense of things—but, assuming that I have things properly estimated (and I do agree accounting for Sun angle might well require another adjustment), I do not see how one can rule out the Brightwater approach (on its own or coupled with Salter-Latham) thinking that the impact on marine ecosystems would be large and could not be minimized by choosing carefully where one used the approach. Best, Mike MacCracken ******* So, given these On 4/16/11 9:41 PM, "Andrew Lockley" < [email protected] > wrote: Russell, My comments below relate to your 'brightwater' proposal. Out of courtesy, I've removed the thread - so I'm not re-posting your comments without consent. If bubble residency times are high, induced densities can be low. If residency times are low, you'll have to greatly increase local concentrations to cause a globally significant, persistent effect. I quote: " Seitz admitted that scaling it to cover an entire ocean would be technically difficult, not because of the energy < http://www.physorg.com/news189059955.html > requirement, which he said would be equivalent to about 1000 windmills, but because of the fact that the bubbles may not last long enough to effectively spread over large areas. " The risk is, therefore, that very much greater local effects may be induced than is desirable, in order to create the necessary global cover. Not only might this affect primary productivity, but also more subtle biological events such as migration, navigation, feeding and breeding. Bioluminescence is likely to be a notable casualty. 'Hot spots' (or should that be cold spots) of concentrated treatment are therefore likely best avoided. The hot-spot effect is not unlike covering a forest in a dense blanket of fog, when the local weather never naturally causes such an effect. I would expect the ecosystem impacts to be very significant, or even catastrophic, especially if the treatment were persistent. Your video and images show the bubble plumes spreading laterally and vertically, rather like slicks. They also show a high optical density, far higher than I would regard as desirable in open ecosystems. Were the bubbles' residence time longer, the local concentrations could be relatively reduced, thus reducing the localised optical impact. Churning the bubbled water into untreated volumes would be desirable, and a towed streamer design with many small bubblers would be beneficial in this regard. Oil survey vessels use such a system, which I understand relies on hydrodynamic forces to distribute hydrophones over a wide track. The behaviour of microbubbles in high concentrations may be entirely different to that in lower concentrations - not least because of the limitations of locally available substances to dwell on the bubble surfaces. I think it would be extremely brave to make detailed predictions when such a large range of complex factors can affect the behaviour of the bubbles (to such an extent that the idea could easily be rendered impractical). Not only are optical effects a consideration, but you also need to consider the ecosystem impact of the surface physics and chemistry. If the microbubbles affect the movement or cycling of detritus and microorganisms, the ecosystem impact could be severe. I've also briefly looked over the maths you're proposing, and I'm not fully reassured by the calculations. I haven't checked the detail of the model you're using, but I'm concerned by the assertion that "The backscattering coefficient (bb) of hydrosols of micron-sized bubbles depends on the fraction of incident light that is intercepted and returned between 90º and 180º." - as, at high densities, there's a significant chance of rescattering of once-reflected light. I can't see how this has been accounted for in your model. Of further serious concern is your proposal to create 'icecaps' in the tropics. Such a localised cooling has the potential to strongly affect ocean overturning circulation, and could possibly induce an anoxic event. I don't think your modelling is robust enough to eliminate this possibility. Furthermore, by concentrating cooling in waterbodies, an intuitive analysis suggests that a reduction in evaporation will result. This has potentially major implications for terrestrial ecosystems and agriculture. Specific research in this regard is merited. I'm sure many of my criticisms have already been considered and discounted, so perhaps you can fill me in? Please don't get me wrong - I like your idea, and I want it to work. It's the most exciting new geoeng idea for a long time. But we need to be honest about the practical limitations of our predictive powers here, and the range of factors which need further study before we can start to hang our hats on these proposals. We also need to make sure that we don't unwittingly advocate a technique which could possibly cause a local or global environmental disaster. A -- 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 . -- 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.
