Considering all effects, what's your view on the ideal height? Andrew
On Tue, 17 Dec 2019, 08:47 Govindasamy Bala, <[email protected]> wrote: > 26 km is probably not going to add any more benefit compared 25 km if you > consider the effect identified in our paper but it is better when > sedimentation effect is considered. More experiments with the NCAR WACCM > model would be good to precisely nail this down. > > On Tue, Dec 17, 2019 at 2:10 PM Andrew Lockley <[email protected]> > wrote: > >> Is 26k less good than 25? >> >> On Tue, 17 Dec 2019, 08:37 Govindasamy Bala, <[email protected]> wrote: >> >>> Andrew, >>> >>> Sedimentation effect works in the same direction as the effect we >>> identified in our study. Therefore, higher the altitude of injection, the >>> better. My judgement: 25 km would be good. >>> >>> On Mon, Dec 16, 2019 at 8:54 PM Andrew Lockley <[email protected]> >>> wrote: >>> >>>> So what's your judgement on the ideal injection altitude? >>>> >>>> Andrew >>>> >>>> On Mon, 16 Dec 2019, 10:36 Govindasamy Bala, <[email protected]> >>>> wrote: >>>> >>>>> Andrew, >>>>> Many modeling groups (e.g. Tilmes and others) have already performed >>>>> simulations that inject aerosols at different heights and thus have >>>>> included the sedimentation effects and many many other effects. These >>>>> studies simulate the NET effects and hence hard to interpret and quantify >>>>> the individual effects. The strength of our ESD paper is that it changes >>>>> only one variable and identifies its individual contribution to the total >>>>> problem. >>>>> >>>>> What we have learnt during the course is that there are too many >>>>> variables in the aerosol SRM problem (transport, location of injection, >>>>> aerosol-cloud interaction, aerosol-radiation interaction, aerosol micro >>>>> physics and the resulting size distribution of the aerosols, etc.) and the >>>>> resulting uncertainties could be too large. This is of course known to >>>>> many >>>>> of us for a long time...... >>>>> >>>>> On Mon, Dec 16, 2019 at 3:41 PM Andrew Lockley < >>>>> [email protected]> wrote: >>>>> >>>>>> If I understand from the email below , you used aerosols with no fall >>>>>> speed. Are experiments planned to simulate aerosol descent? >>>>>> >>>>>> Andrew >>>>>> >>>>>> On Mon, 16 Dec 2019, 05:43 Govindasamy Bala, <[email protected]> >>>>>> wrote: >>>>>> >>>>>>> Andrews, >>>>>>> >>>>>>> We did not do experiments with aerosols above 22 km. It is likely >>>>>>> that the cooling effect will be larger when aerosols are at 25 km. >>>>>>> Beyond >>>>>>> that it is likely that the additional cooling benefits disappear. We >>>>>>> need >>>>>>> more experiments to confirm this. >>>>>>> >>>>>>> The sensitivity to height in our paper arises mainly because of the >>>>>>> increases in stratospheric water vapor (which partly offsets the cooling >>>>>>> efficiency of the aerosols) that is associated with the stratospheric >>>>>>> heating by the aerosols. This increase in stratospheric water vapor is >>>>>>> largest when the aerosols (and the heating) is close to the tropopause. >>>>>>> >>>>>>> In our paper, we have isolated the effect of just one factor. As >>>>>>> Doug has pointed out, the sedimentation effect would also lead to more >>>>>>> cooling if aerosols are injected at higher altitudes... >>>>>>> >>>>>>> Best, >>>>>>> Bala >>>>>>> >>>>>>> On Sun, Dec 15, 2019 at 9:05 PM Douglas MacMartin < >>>>>>> [email protected]> wrote: >>>>>>> >>>>>>>> This is a great study to understand the effectiveness per unit mass >>>>>>>> **in the stratosphere**. Also keep in mind that there’s an >>>>>>>> additional factor, that at lower altitudes it takes higher injection >>>>>>>> rates >>>>>>>> to achieve the same burden in the stratosphere (i.e., lower lifetime at >>>>>>>> lower injected altitude). >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> If the only thing you cared about was cost, then since there are >>>>>>>> existing studies demonstrating that you can design an aircraft to get >>>>>>>> to >>>>>>>> ~20-21km, we roughly know that it could be done, but higher altitude >>>>>>>> injection means less total sulfur injected and hence smaller side >>>>>>>> effects, >>>>>>>> and should be better understood both on the modeling and implementation >>>>>>>> cost as the trade may well be worth it. >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> doug >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> *From:* [email protected] < >>>>>>>> [email protected]> *On Behalf Of *Govindasamy Bala >>>>>>>> *Sent:* Saturday, December 14, 2019 9:38 PM >>>>>>>> *To:* Andrew Lockley <[email protected]> >>>>>>>> *Cc:* geoengineering <[email protected]> >>>>>>>> *Subject:* Re: [geo] Climate system response to stratospheric >>>>>>>> sulfate aerosols: sensitivity to altitude of aerosol layer >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> Dear Andrew, >>>>>>>> >>>>>>>> Thanks for the posting. The heights studied were 16, 19 and 22 km, >>>>>>>> height that are relevant to solar radiation modification problem.. The >>>>>>>> final paragraph in the paper is worth reading to get more quantitative >>>>>>>> information from this modeling study. >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> "To summarize, for the same mass, the efficiency (defined >>>>>>>> >>>>>>>> as changes in surface temperature per Tg S) of volcanic >>>>>>>> aerosol is less when it is prescribed at lower altitudes in the >>>>>>>> stratosphere (Fig. 9). For example, in our simulations, there is >>>>>>>> a surface cooling of 0.44K for each teragram of sulfur placed >>>>>>>> in the stratosphere at about 16 km altitude (100 hPa). There >>>>>>>> is an additional surface cooling of 0.15K per Tg S when the >>>>>>>> prescribed altitude is increased from about 16 km to about >>>>>>>> 22 km (37 hPa)." >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> On Sat, Dec 14, 2019 at 12:55 AM Andrew Lockley < >>>>>>>> [email protected]> wrote: >>>>>>>> >>>>>>>> Poster's note : this has significant implications for the >>>>>>>> engineering of delivery systems. I can't do the pressure altitude >>>>>>>> conversion in my head, but it's a lot higher than what's generally been >>>>>>>> planned for. We're gonna need a bigger boat. >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> https://www.earth-syst-dynam.net/10/885/2019/ >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> Climate system response to stratospheric sulfate aerosols: >>>>>>>> sensitivity to altitude of aerosol layer >>>>>>>> >>>>>>>> *Krishna-Pillai Sukumara-Pillai Krishnamohan et al. *Received: 01 >>>>>>>> May 2019 – Discussion started: 23 May 2019 – Revised: 24 Oct >>>>>>>> 2019 – Accepted: 08 Nov 2019 – Published: 13 Dec 2019 >>>>>>>> >>>>>>>> Abstract >>>>>>>> >>>>>>>> top <https://www.earth-syst-dynam.net/10/885/2019/#top> >>>>>>>> >>>>>>>> Reduction of surface temperatures of the planet by injecting >>>>>>>> sulfate aerosols in the stratosphere has been suggested as an option to >>>>>>>> reduce the amount of human-induced climate warming. Several previous >>>>>>>> studies have shown that for a specified amount of injection, aerosols >>>>>>>> injected at a higher altitude in the stratosphere would produce more >>>>>>>> cooling because aerosol sedimentation would take longer. In this >>>>>>>> study, we >>>>>>>> isolate and assess the sensitivity of stratospheric aerosol radiative >>>>>>>> forcing and the resulting climate change to the altitude of the aerosol >>>>>>>> layer. We study this by prescribing a specified amount of sulfate >>>>>>>> aerosols, >>>>>>>> of a size typical of what is produced by volcanoes, distributed >>>>>>>> uniformly >>>>>>>> at different levels in the stratosphere. We find that stratospheric >>>>>>>> sulfate >>>>>>>> aerosols are more effective in cooling climate when they reside higher >>>>>>>> in >>>>>>>> the stratosphere. We explain this sensitivity in terms of effective >>>>>>>> radiative forcing: volcanic aerosols heat the stratospheric layers >>>>>>>> where >>>>>>>> they reside, altering stratospheric water vapor content, tropospheric >>>>>>>> stability, and clouds, and consequently the effective radiative >>>>>>>> forcing. We >>>>>>>> show that the magnitude of the effective radiative forcing is larger >>>>>>>> when >>>>>>>> aerosols are prescribed at higher altitudes and the differences in >>>>>>>> radiative forcing due to fast adjustment processes can account for a >>>>>>>> substantial part of the dependence of the amount of cooling on aerosol >>>>>>>> altitude. These altitude effects would be additional to dependences on >>>>>>>> aerosol microphysics, transport, and sedimentation, which are outside >>>>>>>> the >>>>>>>> scope of this study. The cooling effectiveness of stratospheric sulfate >>>>>>>> aerosols likely increases with the altitude of the aerosol layer both >>>>>>>> because aerosols higher in the stratosphere have larger effective >>>>>>>> radiative >>>>>>>> forcing and because they have higher stratospheric residence time; >>>>>>>> these >>>>>>>> two effects are likely to be of comparable importance. >>>>>>>> >>>>>>>> -- >>>>>>>> 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 view this discussion on the web visit >>>>>>>> https://groups.google.com/d/msgid/geoengineering/CAJ3C-04wbNfg0E3q_8GtwXay88n_2r%2BhzYfVfrNPjq9SpJd9pg%40mail.gmail.com >>>>>>>> <https://groups.google.com/d/msgid/geoengineering/CAJ3C-04wbNfg0E3q_8GtwXay88n_2r%2BhzYfVfrNPjq9SpJd9pg%40mail.gmail.com?utm_medium=email&utm_source=footer> >>>>>>>> . >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> -- >>>>>>>> >>>>>>>> With Best Wishes, >>>>>>>> >>>>>>>> ------------------------------------------------------------------- >>>>>>>> G. Bala >>>>>>>> Professor >>>>>>>> Center for Atmospheric and Oceanic Sciences >>>>>>>> Indian Institute of Science >>>>>>>> Bangalore - 560 012 >>>>>>>> India >>>>>>>> >>>>>>>> Tel: +91 80 2293 3428; +91 80 2293 2505 >>>>>>>> Fax: +91 80 2360 0865; +91 80 2293 3425 >>>>>>>> Email: [email protected]; [email protected] >>>>>>>> Web:http://dccc.iisc.ac.in/dr_govindasamy_bala_profile.html >>>>>>>> ------------------------------------------------------------------- >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> -- >>>>>>>> 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 view this discussion on the web visit >>>>>>>> https://groups.google.com/d/msgid/geoengineering/CAD7fhV%3Dc5Q4XVod8rAide3VNOmN1uyPbp6B6TCRKij474F_Meg%40mail.gmail.com >>>>>>>> <https://groups.google.com/d/msgid/geoengineering/CAD7fhV%3Dc5Q4XVod8rAide3VNOmN1uyPbp6B6TCRKij474F_Meg%40mail.gmail.com?utm_medium=email&utm_source=footer> >>>>>>>> . >>>>>>>> >>>>>>> >>>>>>> >>>>>>> -- >>>>>>> With Best Wishes, >>>>>>> >>>>>>> ------------------------------------------------------------------- >>>>>>> G. Bala >>>>>>> Professor >>>>>>> Center for Atmospheric and Oceanic Sciences >>>>>>> Indian Institute of Science >>>>>>> Bangalore - 560 012 >>>>>>> India >>>>>>> >>>>>>> Tel: +91 80 2293 3428; +91 80 2293 2505 >>>>>>> Fax: +91 80 2360 0865; +91 80 2293 3425 >>>>>>> Email: [email protected]; [email protected] >>>>>>> Web:http://dccc.iisc.ac.in/dr_govindasamy_bala_profile.html >>>>>>> ------------------------------------------------------------------- >>>>>>> >>>>>>> >>>>> >>>>> -- >>>>> With Best Wishes, >>>>> >>>>> ------------------------------------------------------------------- >>>>> G. Bala >>>>> Professor >>>>> Center for Atmospheric and Oceanic Sciences >>>>> Indian Institute of Science >>>>> Bangalore - 560 012 >>>>> India >>>>> >>>>> Tel: +91 80 2293 3428; +91 80 2293 2505 >>>>> Fax: +91 80 2360 0865; +91 80 2293 3425 >>>>> Email: [email protected]; [email protected] >>>>> Web:http://dccc.iisc.ac.in/dr_govindasamy_bala_profile.html >>>>> ------------------------------------------------------------------- >>>>> >>>>> >>> >>> -- >>> With Best Wishes, >>> >>> ------------------------------------------------------------------- >>> G. Bala >>> Professor >>> Center for Atmospheric and Oceanic Sciences >>> Indian Institute of Science >>> Bangalore - 560 012 >>> India >>> >>> Tel: +91 80 2293 3428; +91 80 2293 2505 >>> Fax: +91 80 2360 0865; +91 80 2293 3425 >>> Email: [email protected]; [email protected] >>> Web:http://dccc.iisc.ac.in/dr_govindasamy_bala_profile.html >>> ------------------------------------------------------------------- >>> >>> > > -- > With Best Wishes, > > ------------------------------------------------------------------- > G. Bala > Professor > Center for Atmospheric and Oceanic Sciences > Indian Institute of Science > Bangalore - 560 012 > India > > Tel: +91 80 2293 3428; +91 80 2293 2505 > Fax: +91 80 2360 0865; +91 80 2293 3425 > Email: [email protected]; [email protected] > Web:http://dccc.iisc.ac.in/dr_govindasamy_bala_profile.html > ------------------------------------------------------------------- > > -- 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 view this discussion on the web visit https://groups.google.com/d/msgid/geoengineering/CAJ3C-04xNuvoL4t217_9MG8UCzfFG3-PXe%3DbX9Fmcx%2B69nKPkA%40mail.gmail.com.
