Oh! Could you point me towards those discussions, papers, etc, describing the mechanism of this? The volcanic H2O paper I just attached discusses lower stratospheric warming's role in it, but if true, what you mention would seem very likely to be involved.....and provide an example of the kind of thing I was wondering about.....Nathan
On Monday, August 11, 2014 3:24:47 AM UTC-4, andrewjlockley wrote: > > There's an intrinsic connection as SRM warms the tropopause > > A > On 11 Aug 2014 04:24, "Nathan Currier" <[email protected] <javascript:>> > 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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