| SOLAR GEOENGINEERING WEEKLY SUMMARY (20 MAY - 26 MAY 2024)Subscribe to our newsletter to receive monthly updates on Solar Geoengineering:
RESEARCH PAPERSVisioni, D., Quaglia, I., & Steinke, I. (2024). A living assessment of different materials for stratospheric aerosol injection—Building bridges between model world and the messiness of reality. Geophysical Research Letters, 51(10), e2024GL108314. Abstract There are obstacles in better understanding the climate impacts associated with new materials that could be used for Stratospheric Aerosol Injections (SAI), like the lack of an integrated framework that combines climate modeling across scales, laboratory studies and small-scale field experiments. Vattioni et al. (2023, https://doi.org/10.1029/2023gl105889) explored one aspect of using alternative, non-sulfate materials for SAI. They investigated how uncertain the response of stratospheric ozone would be to alumina injections for SAI. In their study, they quantify chlorine activation rates in the presence of alumina, and then cascade these uncertainties into estimates of ozone depletion, concluding that alumina might have less detrimental impacts on stratospheric chemistry than sulfate, but with large uncertainties. Their results provide a useful basis upon which future research endeavors combining indoor and outdoor experiments and modeling may be structured to produce robust assessments of SAI impacts, benefits and uncertainties, together with clarifying what kind of research needs to be prioritized.
Laakso, A., Visioni, D., Niemeier, U., Tilmes, S., & Kokkola, H. (2024). Dependency of the impacts of geoengineering on the stratospheric sulfur injection strategy–Part 2: How changes in the hydrological cycle depend on the injection rate and model used. Earth System Dynamics, 15(2), 405-427. Abstract This is the second of two papers in which we study the dependency of the impacts of stratospheric sulfur injections on the model and injection strategy used. Here, aerosol optical properties from simulated stratospheric aerosol injections using two aerosol models (modal scheme M7 and sectional scheme SALSA), as described in Part 1 (Laakso et al., 2022), are implemented consistently into the EC-Earth, MPI-ESM and CESM Earth system models (ESMs) to simulate the climate impacts of different injection rates ranging from 2 to 100 Tg(S) yr−1. Two sets of simulations were run with the three ESMs: (1) regression simulations, in which an abrupt change in CO2 concentration or stratospheric aerosols over pre-industrial conditions was applied to quantify global mean fast temperature-independent climate responses and quasi-linear dependence on temperature, and (2) equilibrium simulations, in which radiative forcing of aerosol injections with various magnitudes compensated for the corresponding radiative forcing of CO2 enhancement to study the dependence of precipitation on the injection magnitude. The latter also allow one to explore the regional climatic responses. Large differences in SALSA- and M7-simulated radiative forcing in Part 1 translated into large differences in the estimated surface temperature and precipitation changes in ESM simulations; for example, an injection rate of 20 Tg(S) yr−1 in CESM using M7-simulated aerosols led to only 2.2 K global mean cooling, while EC-Earth–SALSA combination produced a 5.2 K change. In equilibrium simulations, where aerosol injections were utilized to offset the radiative forcing caused by an atmospheric CO2 concentration of 500 ppm, the decrease in global mean precipitation varied among models, ranging from −0.7% to −2.4% compared with the pre-industrial climate. These precipitation changes can be explained by the fast precipitation response due to radiation changes caused by the stratospheric aerosols and CO2, as the global mean fast precipitation response is shown to be negatively correlated with global mean atmospheric absorption. Our study shows that estimating the impact of stratospheric aerosol injection on climate is not straightforward. This is because the simulated capability of the sulfate layer to reflect solar radiation and absorb long-wave radiation is sensitive to the injection rate as well as the aerosol model used to simulate the aerosol field. These findings emphasize the necessity for precise simulation of aerosol microphysics to accurately estimate the climate impacts of stratospheric sulfur intervention. This study also reveals gaps in our understanding and uncertainties that still exist related to these controversial techniques.
Axebrink, E., Sporre, M. K., & Friberg, J. (2024). High-resolution stratospheric volcanic SO 2 injections in WACCM. EGUsphere, 2024, 1-19. Abstract Aerosols from volcanic eruptions impact our climate by influencing the Earth’s radiative balance. The degree of their climate impact is determined by the location and injection altitude of the volcanic SO2. To investigate the importance of utilizing correct injection altitudes we ran climate simulations of the June 2009 Sarychev eruptions with three SO2 datasets, in the Community Earth System Model Version 2 (CESM2) Whole Atmosphere Community Climate Model Version 6 (WACCM6). We have compared simulations with WACCM’s default 1 km vertically resolved dataset M16 with our two 200 m vertically resolved datasets, S21-3D and S21-1D. The S21-3D is distributed over a large area (30 latitudes and 120 longitudes), whereas S21-1D releases all SO2 in one latitude and longitude grid-box, mimicking the default dataset M16. For S21-1D and S21-3D, 95 % of the SO2 was injected into the stratosphere, whereas M16 injected only 75 % to the stratosphere. This difference is due to the different vertical distribution and resolution of SO2 in the datasets. The larger portion of SO2 injected into the stratosphere for the S21 datasets leads to more than twice as high sulfate aerosol load in the stratosphere for the S21-3D simulation compared to the M16 simulation during more than 8 months. The temporal evolution in AOD from two of our simulations, S21-3D and S21-1D, follows the observations from the space-borne lidar instrument CALIOP closely, while the AOD in the M16 simulation is substantially lower. This indicates that the injection altitude and vertical resolution of the injected volcanic SO2 substantially impact the model’s ability to correctly simulate the climate impact from volcanic eruptions. The S21-3D dataset with the high vertical and horizontal resolution resulted in global volcanic forcing of -0.24 W/m2 during the first year after the eruptions, compared with only -0.11 W/m2 for M16. Hence, our study high-lights the importance of using high-vertically resolved SO2 data in simulations of volcanic climate impact, and calls for a re-evaluation of further volcanic eruptions.
Rowland, Z. C., Hoffmann, F., Glassmeier, F., Steinke, I., & Russchenberg, H. (2024). Sensitivities of Marine Cloud Brightening Studied with a Lagrangian Cloud Model (No. EGU24-4114). Copernicus Meetings. Abstract Marine cloud brightening (MCB) is a proposed climate engineering technique in which shallow liquid clouds are deliberately seeded with aerosol particles to increase their albedo and lifetime. Development of accurate models is essential to assess the feasibility of MCB; however, this is complicated by the large number of interacting microphysical processes that occur during cloud formation and the many environmental parameters that influence them. To simulate these microphysical processes in the required detail, a Lagrangian cloud model has been coupled to a simple adiabatic parcel model for this study. Using this modelling framework, a sensitivity analysis is performed to determine the susceptibility of MCB to the aerosol particle size distribution, meteorological conditions, and several cloud microphysical choices. Attention is paid to the effect of varying the number of giant cloud condensation nuclei (GCCN) in the aerosol distribution, as these are known to enhance precipitation, with potentially deleterious effects to MCB. The results of this analysis provide insight for understanding the susceptibility of cloud formation to environmental conditions and practical considerations for any possible future MCB implementation.
Chen, C. C., Richter, J. H., Lee, W. R., Tye, M. R., MacMartin, D. G., & Kravitz, B. (2024). Climate impact of marine cloud brightening solar climate intervention under a susceptibility based strategy simulated by CESM2. Authorea Preprints. Abstract The efficiency of marine cloud brightening in cooling Earth’s surface temperature is investigated by using a medium ensemble of simulations with the Community Earth System Model version 2 (CESM2). Various cloud seeding schemes based on susceptibility are examined to determine what area extent will be required to induce 1oC cooling under SSP2-4.5. The results indicate that cloud seeding over 5% of the ocean area is capable of achieving this goal. Under this seeding scheme, cloud seeding is mainly deployed over lower latitudes where strong surface temperature and precipitation responses are induced. The simulations also reveal that the 5% cloud seeding scheme induces an overall reduction in global precipitation, with an increase over land and a decrease over the ocean.
Laakso, A., Visioni, D., Niemeier, U., Tilmes, S., & Kokkola, H. (2024). Dependency of the impacts of geoengineering on the stratospheric sulfur injection strategy–Part 2: How changes in the hydrological cycle depend on the injection rate and model used. Earth System Dynamics, 15(2), 405-427.
WEB POSTSFrom Pollution to Solution (Cremieux Recueil) Cremieux RecueilCrémieux recently tweeted that peak pollution might have been reached. Among the jubilant voices in the comments, there were a few casting a keen eye towards the lack of sulfur dioxide (SO₂), a compound notorious for its role in acid rain. Beyond its infamous reputation, SO₂ holds a lesser-known potential as a powerful tool to combat global warming w… 3 days ago · 16 likes · 2 comments · Andrew Song
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YOUTUBE VIDEOSClimate Interventions: Solar Geoengineering | The Institute for Science & Policy "In our three-part Climate Interventions series, we look at the scientific understanding and uncertainties around a range of interventions to reduce greenhouse gas emissions and cool the planet, along with a robust discussion on ethics, risks, and governance. In this session, we are exploring solar geoengineering approaches, also known as solar radiation modification/management (SRM), which seek to cool the planet by reflecting some of the incoming energy back to space. To date, most of the research approaches have been restricted to computer modeling. Some proponents, however, are looking to field experiments, and perhaps ultimately, wide-scale deployment. While some options might help ameliorate the impacts of climate change, they also might pose serious risks. Join a panel of experts for breakfast at the Denver Museum of Nature and Science exploring the latest deliberations around research, governance, impacts, and more."
Can geoengineering help us solve climate change? | The Excerpt | USA TODAY "As the world warms and aspirations to reach net-zero carbon emissions slide further and further away, climate scientists and engineers are looking at solutions, that to some, might sound like they’re straight out of science fiction. By taking on climate control with technology, experts say geoengineering can be a tool to help mitigate and remove greenhouse gases from the climate system and may be essential to reducing global temperatures. Wake Smith, author of “Pandora’s Toolbox: The Hopes and Hazards of Climate Intervention,” and a lecturer at the Yale School of the Environment, joins The Excerpt to discuss these developments in climate intervention."
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