Any statement of the form "artificial stratospheric sulfate injection would induce significant X" is obviously wrong, given that at a minimum any effect depends on how much you do. And we need an assessment of the overall trade-offs, not mindless throwing out of options based on any one single effect.
In the case of ozone, there's lots of papers on this, and there will be more; the answer of course depends on how much you do, on what latitudes you inject at, on when you start, but there's also a lot more to it than just the heterogeneous chemistry response; when you include all of the dynamical and chemical responses then in some places total column ozone goes up (over Antarctic it consistently goes down - though if you start in 2035 to maintain temperatures at 2030 levels, then in CESM(WACCM) simulations, Antarctic ozone levels might drop to levels not seen since 2025... is that a reason to ignore SAI?) On Fri, Oct 17, 2025 at 12:45 PM Oeste <[email protected]> wrote: > Hi Clive and Oswald, > > The authors of the paper below state, that enhanced stratospheric sulfate > aerosol levels from volcanic eruptions or artificial stratospheric sulfate > injection would induce *significant* stratospheric ozone depletion. > > Volcanic sulfate injections are only during the volcanic maximum eruption > period active. These eruption periods last very seldom more than a month. > Stratospheric Aerosol Injection (SAI) periods are longer than 100 years. > Hence the skin cancer inducing UV-C radiation problem induced by > the stratospheric ozone depletion will also last for more than 100 years. > > Because we know some much more economic and efficient climate restoration > methods this should make no problems for climate restoration. > > Franz > > > Am 17.10.2025 um 13:32 schrieb Geoengineering News: > > https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2025JD043786?af=R > > *Authors: *Laila V. Howar, Ross J. Salawitch, David M. Wilmouth, Eric J. > Hintsa, Jennifer S. Hare, Thomas F. Hanisco, Jason M. St. Clair, Erin R. > Delaria, Elliot L. Atlas, Sue Schauffler, Kate R. Smith, Jessica B. Smith, > Bradley D. Hall, Fred L. Moore, Jasna V. Pittman, Bruce Daube, T. Paul Bui, > Yaowei Li, Frank N. Keutsch, David S. Sayres, Steven C. Wofsy, Jonathan > Dean-Day, Stephen Donnelly, Victoria A. Treadaway, James G. Anderson, > Cameron R. Homeyer, Kenneth P. Bowman > > *14 October 2025* > > https://doi.org/10.1029/2025JD043786 > > *Abstract* > Studies have suggested that ClO could be enhanced within convectively > influenced air masses in the North American Monsoon Anticyclone due to low > temperature and elevated water mixing ratio conditions that are conducive > to chlorine activation, potentially leading to significant loss of ozone in > the midlatitude lowermost stratosphere. We analyze in situ measurements of > temperature, pressure, ClO, ClONO2, H2O, NO2, aerosol surface area density > (SAD), and organic chlorine species obtained by instruments aboard the NASA > ER-2 over the continental US during the Dynamics and Chemistry of the > Summer Stratosphere (DCOTSS) campaign to show that chlorine activation > large enough to affect loss of ozone was not observed, for the summers of > 2021 and 2022. During both deployments, tropopause-overshooting convection > with water vapor and temperature conditions suitable for chlorine > activation were sampled. Due to their relatively young chemical age, most > of these cold and wet air masses had abundances of inorganic chlorine (Cly) > too low to support eventual enhancements of ClO that would lead to > widespread ozone depletion. Even in the few air masses with higher levels > of Cly, the abundance of nitrogen oxides was elevated and the ratio of > ClONO2 to Cly was observed to be very low, limiting the availability of > ClONO2 to react with HCl and sustain chlorine activation. However, we show > that for the average chemical and meteorological conditions of cold, wet, > overshooting air parcels observed during DCOTSS, significant chlorine > activation could occur if stratospheric sulfate SAD were enhanced by major > volcanic eruptions or *climate intervention efforts.* > > *Plain Language Summary* > Stratospheric ozone shields life on Earth from the Sun's harmful > ultraviolet rays. Mixed-phase chemical reactions, which typically occur > only at very low temperatures, produce large amounts of chlorine monoxide > (ClO), a chemical that rapidly depletes stratospheric ozone. Previous > studies have hypothesized that abundances of ClO, capable of leading to > substantial ozone depletion, could be found in the midlatitude stratosphere > when large storms inject water vapor high into the stratosphere. During the > Dynamics and Chemistry of the Summer Stratosphere (DCOTSS) NASA ER-2 > aircraft field campaign, magnitudes of ClO capable of causing significant > ozone depletion were not observed within cold and wet air masses. Although > large amounts of water vapor were injected into the stratosphere by these > storms, the air masses lacked the chemical conditions necessary for > chlorine activation to cause significant ozone loss. Additionally, our > modeling analysis of data collected during DCOTSS indicates that the > stratospheric injection of sulfate, in an effort to mitigate global > warming, could increase the risk of chlorine activation in the midlatitude > lower stratosphere. > > *Key Points* > > Observations of ClO from the Dynamics and Chemistry of the Summer > Stratosphere mission show no evidence of heterogeneous chlorine activation > > Chlorine activation was limited by the availability of inorganic chlorine > and the partitioning between the two major chlorine reservoirs > > Enhancement of sulfate aerosol surface area would increase the potential > for chlorine activation in the midlatitude stratosphere > > *Source: AGU* > > -- > 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 visit > https://groups.google.com/d/msgid/geoengineering/CAHJsh98R7S8W9cxJ_fhJYFPfU_eU-7DBwFS7dPbFr0cgc8sPQQ%40mail.gmail.com > <https://groups.google.com/d/msgid/geoengineering/CAHJsh98R7S8W9cxJ_fhJYFPfU_eU-7DBwFS7dPbFr0cgc8sPQQ%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > > -- > 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 visit > https://groups.google.com/d/msgid/geoengineering/490309d7-0d6a-4ef6-bf9e-f2ff7805afe1%40gm-ingenieurbuero.com > <https://groups.google.com/d/msgid/geoengineering/490309d7-0d6a-4ef6-bf9e-f2ff7805afe1%40gm-ingenieurbuero.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "geoengineering" group. 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