Poster's note: Reviewer 2 did a podcast on the paper: "*The Radiative and Cloud Responses to Sea Salt Aerosol Engineering in GFDL Models."* Title of podcast: Does MCB actually work? MahfouzReviewer 2 does geoengineering <https://podcasts.apple.com/us/podcast/reviewer-2-does-geoengineering/id1529459393>
*Some links to listen to the podcast: * https://podcasts.apple.com/us/podcast/does-mcb-actually-work-mahfouz/id1529459393?i=1000602560752 https://podcasts.google.com/feed/aHR0cHM6Ly9hbmNob3IuZm0vcy8zMjkzZDIzMC9wb2RjYXN0L3Jzcw/episode/OTgzZWVlN2ItMjFjNC00NmNkLTg3ZTUtNTRiYzQyMzY5YTMy?ep=14Naser https://open.spotify.com/show/2KSB1lU18qh5gYIRDYPJMb *Description: * "Mahfouz explains some big problems with MCB to @geoengineering1. Can we fill in the knowledge gaps, before it's too late to use MCB? Paper: "The Radiative and Cloud Responses to Sea Salt Aerosol Engineering in GFDL Models" ( https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2022GL102340)" On Fri, Feb 24, 2023, 1:46 PM Geoengineering News < geoengineeringne...@gmail.com> wrote: > https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2022GL102340 > > *Authors* > > Naser G. A. Mahfouz > <https://agupubs.onlinelibrary.wiley.com/action/doSearch?ContribAuthorRaw=Mahfouz%2C+Naser+G+A> > , Spencer A. Hill > <https://agupubs.onlinelibrary.wiley.com/action/doSearch?ContribAuthorRaw=Hill%2C+Spencer+A> > , Huan Guo > <https://agupubs.onlinelibrary.wiley.com/action/doSearch?ContribAuthorRaw=Guo%2C+Huan> > , Yi Ming > <https://agupubs.onlinelibrary.wiley.com/action/doSearch?ContribAuthorRaw=Ming%2C+Yi> > First published: *17 January 2023* > > https://doi.org/10.1029/2022GL102340 > > Abstract > > Marine cloud brightening is a proposal to counteract global warming by > increasing sea salt aerosol emissions. In theory, this increases the cloud > droplet number concentration of subtropical marine stratocumulus decks, > increasing cloud brightness and longevity. However, this theoretical > progression remains uncertain in coupled climate models, especially the > response of liquid water path and cloud fraction to aerosol seeding. We use > the GFDL CM4 climate model to simulate marine cloud brightening following > the published G4sea-salt protocol, in which sea salt aerosol emissions are > uniformly increased over 30 S–30 N in addition to standard forcings from a > SSP2-4.5 future warming scenario. The perturbed radiative and cloud > responses are temporally stable though spatially heterogeneous, and direct > scattering by the added sea salt predominates over changes to cloud > reflectance. In fact, feedbacks in the coupled simulation lead to a net > warming, rather than cooling, response by clouds. > Key Points > > > - > > Temporally stable climate response to increased sea salt aerosol in > GFDL’s AM4 and CM4 models following the G4sea-salt protocol > - > > Dominant role of direct aerosol effects in both models as the indirect > aerosol–cloud effects are counterbalanced by cloud feedbacks in CM4 > - > > Uncertain spatial radiative and cloud responses necessitating further > constraining to yield detailed mechanistic understanding > > Plain Language Summary > > With calls for climate action rising, some countries and groups may be > looking at counteracting global warming. As reducing emissions of > greenhouse gases remains elusive, and while the results of climate change > manifest in extreme events and weather records, state or private actors may > look for active engineering solutions which remain hypothetical and not > fully scientifically understood. Using premier climate models at NOAA GFDL, > we examine one form of climate engineering, marine cloud brightening, aimed > at increasing radiation reflected back to space by increasing sea salt > aerosol emissions in the marine tropics. We find the climate response to a > protocol of this scheme temporally stable over the time period of the > simulation, though spatially uncertain. Moreover, the response is largely > dominated by effects resulting from the direct interactions between aerosol > particles and solar radiation, and not via clouds. Our results paint a more > nuanced picture than previous studies and as such raise more questions and > uncertainties about proposals for marine cloud brightening, at least > through the prism of state-of-the-art climate models. > [image: Details are in the caption following the image] > <https://agupubs.onlinelibrary.wiley.com/cms/asset/d14456d4-e88c-452b-b43e-7f6b21814a38/grl65393-fig-0001-m.jpg> > Figure 1 > Caption > > Annual global-means shortwave radiation imbalance atop the atmosphere (SWR > TOA) from the fixed-sea surface temperature simulation (2020–2030) and the > coupled simulation (2020–2090). The all-sky (All) radiation is decomposed > into the conventional clear-sky (Clear) and the difference between all-sky > and clear-sky (All − Clear) as well as into the Ghan (2013 > <https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2022GL102340#grl65393-bib-0010>) > components: the cloud radiative (Cloud), surface albedo (Surface), and > direct radiative (Direct) effects. > > > [image: Details are in the caption following the image] > <https://agupubs.onlinelibrary.wiley.com/cms/asset/fd18f63b-f452-4a17-b526-3e9b4281eb77/grl65393-fig-0002-m.jpg> > Figure 2 > Caption > > As in Figure 1 > <https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2022GL102340#grl65393-fig-0001> > but > spatially averaged over 2020–2030 for AM4 and 2035–2065 for CM4, with > hatched regions corresponding to statistically insignificant differences. > > > [image: Details are in the caption following the image] > <https://agupubs.onlinelibrary.wiley.com/cms/asset/da7df979-800b-4bd6-b2cc-64f14924ab70/grl65393-fig-0004-m.jpg> > Figure 4 > Caption > > The regional (NP, SP, and SA) and global cloud properties and the Ghan > radiative components. > > *Source: AGU* > > > -- You received this message because you are subscribed to the Google Groups "geoengineering" group. 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