There's an intrinsic connection as SRM warms the tropopause A On 11 Aug 2014 04:24, "Nathan Currier" <[email protected]> wrote:
> Hi, Andrew - I fully agree, and really enjoyed your post "SRM > interaction with atmospheric anomalies (plus water)" > of several days ago, which had mentioned the importance of "folding > events." > > In this case, I was particularly trying to bring up whether there might be > evidence sitting right in front of us coming from > Pinatubo itself, but perhaps somewhat obscured from our thoughts by the > "questionable meme" of Pinatubo as a primary > demonstration of "cooling the planet", that stratospheric SRM might > inherently contain forcings of opposing signs - such > that its radiative effects would always be the net effects of both > negative and positive forcings from its various dynamics. > Folding events could potentially get messy with geoE, but I don't think > one could say there's any intrinsic connection > (at least I haven't heard of one). > > If it were true that both + and - forcings are always there with this kind > of SRM, it might of course still work, but this should lower our > confidence > level in the concept's ultimate viability considerably, because as I say, > you'd really have to keep track of all slight but longer-term positive > radiative > signals it is putting into the climate system (i.e., cooling the > stratosphere, warming us), since you certainly need some degree of > prolongation for the technique > to have much value......and of course, these are just the kinds of > things where we currently seem to know quite little......... > > Cheers, > > Nathan > > > > > On Sunday, August 10, 2014 5:17:04 AM UTC-4, andrewjlockley wrote: >> >> Great point, Nathan. However, you're ignoring an additional issue. >> Warming of the tropopause means it's easier for water to convect or fold in >> to the stratosphere. This is a potentially serious problem, and one I put >> on the list of unknowns already. >> >> Bulk air movements also bring more methane into the stratosphere, which >> ultimately end up as water. >> >> My view is that we need urgent improvements in our ability to monitor and >> model the tropopause, if we are to have a hope of making SRM predictable >> and safe. >> >> A >> On 10 Aug 2014 04:39, "Nathan Currier" <[email protected]> wrote: >> >>> One very widespread geoengineering 'meme' concerns stratospheric SRM >>> and Pinatubo. One reads about it continuously - "like Pinatubo," we will >>> “cool the planet” through stratospheric aerosols. How real is this? >>> Pinatubo clearly cooled the planet *initially*, but are we sure – really >>> sure – that it cooled the planet at all temporal scales? When you turn >>> on a conventional coal plant, it, too, “cools the planet”, if you care to >>> look only at the initial response. >>> >>> There is no discussion, as far as I remember, on the causes of the >>> increased stratospheric water vapor changes in Solomon et al 2010 that I >>> brought up recently at this group, a paper suggesting considerable climate >>> warming from increased stratospheric H2O. In the attached paper, there’s >>> discussion of how volcanic eruptions might impact stratospheric water >>> vapor, causing a pulse of increased water vapor over 5-10 years. Although >>> the volcano injects water vapor itself, its initial impact is actually to >>> *dry* the stratosphere, since the SO2 reaction uses up so much water >>> vapor, meaning that the much longer pulsed increase must come from >>> perturbations in the stratospheric chemistry/climate itself. One question I >>> wonder about is how intrinsically tied to the sulfur itself these H2O >>> pulses might be, perhaps because of changes in methane oxidation, of the >>> kind I was hypothesizing before? In the paper, the modeled increased >>> forcing of roughly +.1w/m2 might seem modest, compared to the initial >>> large negative forcing of –3w/m2 or so, but one lasts a year, the other >>> possibly a decade, and how accurate are these modeled estimates? It is >>> clearly far easier to recognize the sudden cooling from the eruption when >>> it takes place, than a slight warming signal persisting through a much >>> longer period of time in an already warming climate system. Yet clearly >>> this is vital to understand if anyone is going to be doing useful >>> geoengineering based on this. >>> >>> It’s interesting that in the Solomon the water vapor increase is noted >>> to have gone into a considerable decline around 2000-2003, around a decade >>> after Pinatubo. Further, it is important to note that the complex dynamics >>> leading to these entangled positive and negative forcings from a single >>> pulse will almost certainly be shifted by the sheer act of continuous >>> prolongation inherent in geoengineering, so the constant Pinatubo meme >>> becomes a little....empty? >>> >>> Cheers, Nathan >>> >>> On Tuesday, August 5, 2014 2:38:34 PM UTC-4, kcaldeira wrote: >>>> >>>> Folks, >>>> >>>> I am supposed to give a keynote talk at CEC14 in two weeks. For this >>>> talk, I would like to try to develop a list of oft-cited memes that many >>>> assume are established facts, but which may not in fact be true. >>>> >>>> I am thinking of things like: "With solar geoengineering, there will be >>>> winners and losers." "Termination risk is an important reason not to engage >>>> in solar geoengineering." "Solar geoengineering will cause widespread >>>> drying." >>>> >>>> I don't want to discuss all of these things here but simply to develop >>>> a list. You could help me by sending an email answering the questions: >>>> >>>> 2a. What memes are out there which many "experts" regard as >>>> well-established facts but which in fact might not be correct? >>>> >>>> 2b. Why do you suspect the correctness of that meme? >>>> >>>> 2c. (optional) Can you provide a citation or a link to where someone is >>>> assuming the meme is true? >>>> >>>> Thoughtful responses would be most appreciated. If you want to start >>>> discussion about a meme, please do so in a separate thread so that this >>>> thread can be easily used to develop a list. >>>> >>>> Thanks, >>>> >>>> Ken >>>> >>>> _______________ >>>> Ken Caldeira >>>> >>>> Carnegie Institution for Science >>>> Dept of Global Ecology >>>> 260 Panama Street, Stanford, CA 94305 USA >>>> +1 650 704 7212 [email protected] >>>> http://dge.stanford.edu/labs/caldeiralab >>>> https://twitter.com/KenCaldeira >>>> >>>> Assistant: Dawn Ross <[email protected]> >>>> >>>> -- >>> You received this message because you are subscribed to the Google >>> Groups "geoengineering" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to [email protected]. >>> To post to this group, send email to [email protected]. >>> Visit this group at http://groups.google.com/group/geoengineering. >>> For more options, visit https://groups.google.com/d/optout. >>> >> -- You received this message because you are subscribed to the Google Groups "geoengineering" group. 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