* * * Hello again Alan,
It is true that to absolutely KNOW things in this virgin and complex territory is extremely difficult, but to take your points:- I imagine a field experiment extending over perhaps 6 weeks, in order to encompass a variety of meteorological conditions.. Three days is a rough figure for the estimated average duration in the atmosphere of the sprayed seawater aerosol, almost all of which will fall back into the oceans. Unless this late-night calculation is wrong, the ratio of the area of the earth to the 100 x 100 km seeded area is about 50,000, although there is bound to be some influence outside this seeding area, as you surmise. The number of seawater aerosol introduced naturally into the oceanic atmosphere via white-capping etc would be much greater than that resulting from our spraying . If our technique worked as we hope ? which requires satisfactory resolution of technological and other problems ? the seeding could produce a local cloud-albedo enhancement of around 20 to 30%, which should be readily detectable via satellite and in-cloud measurements. Best Wishes, John. Quoting Alan Robock <[email protected]>: > Dear John, > > If you only do it for a few days, how will you detect a signal? And > how do you know that perturbing 10,000 km2 will not affect a larger > area? > > Alan Robock, Professor II (Distinguished Professor) > Department of Environmental Sciences > Rutgers University > 14 College Farm Road > New Brunswick, NJ 08901 > > [email protected] > http://www.envsci.rutgers.edu/~robock/ > Sent from my iPhone. +1-732-881-1610 > > On Sep 27, 2010, at 11:44 PM, John Latham > <[email protected]> wrote: > >> Hello Alan and colleagues, >> I agree with you, Alan, that mounting a comprehensive field study of >> the climatological ramifications of the deployment of SRM schemes >> would be a mammoth, highly protracted and perhaps impossible >> endeavour, but I would like to make the point that field-testing of >> the cloud brightening geoengineering idea could be undertaken >> without significant climatogical repercussions. >> A limited area (say 100 x 100 km) field experiment designed to >> assess the quantitative viability of this SRM scheme (and at the >> same time to examine aerosol-cloud interactions using advertently >> generated seawater aerosol) could be conducted without climatically >> damaging effects since the lifetime of the generated aerosol in the >> marine boundary layer is a few days. Such a study would be very >> similar to and no more complex than the highly successful >> international VOCALS field study of marine stratocumulus clouds >> conducted in 2008 off Chile & Peru, and directed by Rob Wood of the >> University of Washington. >> All Best, John. >> >> >> >> >> >> >> >> Quoting Alan Robock <[email protected]>: >> >> > Dear Ken, >> > >> > I think you are being rather picky with words. In any case, I never >> > said it cannot be tested. I said it cannot be fully tested in a >> > real-world in situ experiment without full-scale implementation, >> > because the climate signal will be drowned out by chaotic climate >> > variations and because injecting into a pristine stratosphere cannot >> > test injecting into an existing cloud. Of course computers can be >> > used for testing. That is what I do, and I advocate much more of it. >> > The statement below refers to in situ experimentation. >> > >> > >> > Alan >> > >> > Alan Robock, Professor II (Distinguished Professor) >> > Editor, Reviews of Geophysics >> > Director, Meteorology Undergraduate Program >> > Department of Environmental Sciences Phone: +1-732-932-9800 x6222 >> > Rutgers University Fax: +1-732-932-8644 >> > 14 College Farm Road E-mail: [email protected] >> > New Brunswick, NJ 08901-8551 USA http://envsci.rutgers.edu/~robock >> > >> > >> > On 9/27/2010 12:00 PM, Ken Caldeira wrote: >> >> Folks, >> >> >> >> Robock et al and Fleming have both asserted that "geoengineering >> >> cannot be tested". >> >> >> >> Robock et al (Science, 2010): /"We argue that geoengineering cannot >> >> be tested without full-scale implementation."/ >> >> Fleming (Slate): "/Global climate engineering is untested and >> >> untestable.../" >> >> >> >> These statements seem either trivially true or patently false, >> >> depending on interpretation. >> >> >> >> *Trivially true:* /If the only thing that you are willing to >> >> consider a test is the thing itself, then trivially there is no test >> >> other than the thing itself./ >> >> >> >> *Patently false:* /There are many tests that can be done that can >> >> help us understand possible consequences of a geoengineering >> >> deployment./ >> >> >> >> One could imagine someone saying in the United States in the 1950's, >> >> "There is no way you can test the proposed interstate highway >> >> system, because you will not understand all its effects until it has >> >> been deployed." This is true, in the sense that you could not >> >> predict in advance detailed effects that the interstate highway >> >> system would have on the spread of suburbia, traffic jams, the rise >> >> of the SUV, and so on. >> >> >> >> But, in the 1950's they could have tested the concrete, built a >> >> small stretch of road and learned about its construction and use >> >> etc. Would we say "/The interstate highway system cannot be tested >> >> without full-scale implementation?/" Would we say "T/he interstate >> >> highway system is untested and untestable?/" I think we would say, >> >> "There are plenty of tests we can do, but of course we will not >> >> understand the full consequences of our implementation until the >> >> implementation is complete." >> >> >> >> We perform tests to improve our understanding. We never have full >> >> understanding of consequences of our actions before we act. We >> >> hopefully act in ways that will have the greatest rational >> >> expectation of positive outcomes. We do research to avoid having >> >> rational expectations that do not accord with facts on the ground. >> >> >> >> Many people have regarded Mt Pinatubo as performing a natural >> >> experiment of geoengineering -- a test of the idea of solar >> >> radiation management. Like all tests, Mt Pinatubo was not a perfect >> >> test (e.g., the aersols were not maintained in the stratosphere, >> >> etc). Nevertheless, Mt Pinatubo has functioned as a natural test of >> >> some of the concepts underlying solar radiation management. >> >> >> >> In 2003, Alan Robock wrote a paper called "Introduction: Mt. >> >> Pinatubo as a test of climate feedback mechanisms". >> >> (http://climate.envsci.rutgers.edu/pdf/VEAChapter1_Robocknew.pdf). >> >> How is it logically possible that Mt Pinatubo could function as a >> >> test of climate feedback mechanisms, but not of geoengineering (ie >> >> SRM), when those climate feedback mechanisms are central to the >> >> climate system response to any geoengineering effort? >> >> >> >> Furthermore, hasn't Alan claimed to have tested geoengineering >> >> concepts in his climate models and found them wanting? How can you >> >> have it both ways: testing geoengineering concepts and claiming the >> >> concepts are untestable? >> >> >> >> The list of possible useful geoengineering tests could be a long >> >> one, and includes tests of small scale physics, climate model >> >> simulations, observations of climate variability, ecosystem >> >> experiments, observations of behavior of natural or introduced >> >> particles on stratospheric transport and chemistry, small scale or >> >> short-term deployments, etc. (I am not advocating all of these, just >> >> listing them.) >> >> >> >> It seems odd, when there are a number of people eager to perform a >> >> wide range of tests on geoengineering concepts, to have a small >> >> minority claiming that these concepts simply can't be tested >> >> (especially when members of that minority have themselves been >> >> involved in testing geoengineering concepts). >> >> >> >> So, do the people who say that "geoengineering can't be tested" mean >> >> something that is both true and substantive (i.e., couldn't also >> >> have been said of, for example, the development of the US interstate >> >> highway system)? If so, it would be interesting to hear what this >> >> non-trivial interpretation might be. >> >> Best, >> >> >> >> Ken >> >> >> >> >> >> ___________________________________________________ >> >> Ken Caldeira >> >> >> >> Carnegie Institution Dept of Global Ecology >> >> 260 Panama Street, Stanford, CA 94305 USA >> >> +1 650 704 7212 [email protected] >> >> <mailto:[email protected]> >> >> http://dge.stanford.edu/labs/caldeiralab @kencaldeira >> >> -- >> >> 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. >> > >> > >> -- >> John Latham >> >> [email protected] & [email protected] >> >> Tel. 303-444-2429 (H) & 303-497-8182 (W) > -- John Latham [email protected] & [email protected] Tel. 303-444-2429 (H) & 303-497-8182 (W) -- You received this message because you are subscribed to the Google Groups "geoengineering" group. 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