| SOLAR GEOENGINEERING WEEKLY SUMMARY (22 APRIL - 28 APRIL 2024) Subscribe to our newsletter to receive monthly updates on Solar Geoengineering:
RESEARCH PAPERSYu, F., Anderson, B. E., Pierce, J. R., Wong, A., Nair, A., Luo, G., & Herb, J. (2024). On Nucleation Pathways and Particle Size Distribution Evolutions in Stratospheric Aircraft Exhaust Plumes with H2SO4 Enhancement. Environmental Science & Technology. Abstract Stratospheric aerosol injection (SAI) is proposed as a means of reducing global warming and climate change impacts. Similar to aerosol enhancements produced by volcanic eruptions, introducing particles into the stratosphere would reflect sunlight and reduce the level of warming. However, uncertainties remain about the roles of nucleation mechanisms, ionized molecules, impurities (unevaporated residuals of injected precursors), and ambient conditions in the generation of SAI particles optimally sized to reflect sunlight. Here, we use a kinetic ion-mediated and homogeneous nucleation model to study the formation of H2SO4 particles in aircraft exhaust plumes with direct injection of H2SO4 vapor. We find that under the conditions that produce particles of desired sizes (diameter ∼200–300 nm), nucleation occurs in the nascent (t < 0.01 s), hot (T = 360–445 K), and dry (RH = 0.01–0.1%) plume and is predominantly unary. Nucleation on chemiions occurs first, followed by neutral new particle formation, which converts most of the injected H2SO4 vapor to particles. Coagulation in the aging and diluting plumes governs the subsequent evolution to a narrow (σg = 1.3) particle size distribution. Scavenging by exhaust soot is negligible, but scavenging by acid impurities or incomplete H2SO4 evaporation in the hot exhaust plume and enhanced background aerosols can matter. This research highlights the need to obtain laboratory and/or real-world experiment data to verify the model prediction.
Yu, F., Anderson, B. E., Pierce, J. R., Wong, A., Nair, A., Luo, G., & Herb, J. (2024). On Nucleation Pathways and Particle Size Distribution Evolutions in Stratospheric Aircraft Exhaust Plumes with H2SO4 Enhancement. Environmental Science & Technology. Abstract Sulfur-rich volcanic eruptions happen sporadically. If Stratospheric Aerosol Injection (SAI) were to be deployed, it is likely that explosive volcanic eruptions would happen during such a deployment. Here we use an ensemble of Earth System Model simulations to show how changing the injection strategy post-eruption could be used to reduce the climate risks of a large volcanic eruption; the risks are also modified even without any change to the strategy. For a medium-size eruption (10 Tg-SO2) comparable to the SAI injection rate, the volcanic-induced cooling would be reduced if it occurs under SAI, especially if artificial sulfur dioxide injections were immediately suspended. Alternatively, suspending injection only in the eruption hemisphere and continuing injection in the opposite would reduce shifts in precipitation in the tropical belt and thus mitigate eruption-induced drought. Finally, we show that for eruptions much larger than the SAI deployment, changes in SAI strategy would have minimal effect.
Smith, W., Bartels, M., Boers, J., & Rice, C. (2024). On thin ice: Solar geoengineering to manage tipping element risks in the cryosphere by 2040. Abstract Tipping elements are features of the climate system which can display self-reinforcing and non-linear responses if pushed beyond a certain threshold (the “tipping point”). Models suggest that we may surpass several of these tipping points in the next few decades, irrespective of which emissions pathway humanity follows. Some tipping elements reside in the Arctic and Antarctic and could potentially be avoided or arrested via a solar geoengineering program only at the poles. This paper considers the utility of proactively developing the capacity to respond to emergent tipping element threats at the poles as a matter of risk management. It then examines both the air and ground infrastructure that would be required to operationalize such capability by 2040 and finds that this would require a funded launch decision by a financially credible actor by roughly 2030.
CONFERENCE PAPERSChehab, M., Herbin, H., Gosselin, S., Bizet, V., & Petitprez, D. (2024). Aerosols complex refractive indices determination from far infrared to UV: application to dust and residual ashes of biomass burning (No. EGU24-10689). Copernicus Meetings. Abstract Due to their ability to absorb and scatter solar radiation, major injections of aerosols can have a significant effect on the atmosphere including impacts on the radiation balance of the Earth and changes in temperature. Given the variability and spatial heterogeneity of their concentration, size and chemical composition, it is important to quantify these aerosols, from remote sensing techniques, in order to better identify their sources and understand their environmental impact from regional to global scale. Satellite instruments, such as the Infrared Atmospheric Sounding Interferometer (IASI) and the Atmospheric Infrared Sounder AIRS for the thermal IR region and FORUM for the far infrared, can give us information about chemical composition (Alalam et al. 2022) and microphysical parameters of the aerosols such as the effective radius, concentration and mass (Deguine et al. 2023). Nonetheless, these techniques require accurate information about the optical properties, specifically the complex refractive index (CRI) .CRI databases available in the literature however, span over limited wavelength ranges and provide mainly reflectance measurements on bulk materials or pressed pellets. In particular, the latter can have several limitations such as the modification of the microphysical properties of the particles (size distribution and morphology). Furthermore, in pellet samples, the particles are present in a compressed matrix causing modifications of the vibrational modes. For bulk measurements, there is strong underestimation of the scattering signal. Therefore, the optical constants coming from such techniques are not fitted for aerosols and atmospheric applications (McPheat et al. 2002). We present an improved retrieval methodology combining an experimental setup that allows simultaneously the measurement of high spectral-resolution extinction spectra (up to 0.5 cm-1) from far infrared (FIR) (50 µm /200 cm-1) up to UV (0.25 µm /40,000 cm-1) and the recording of the size distribution of both fine and coarse particles (Hubert et al. 2017). Introducing these experimental measurements in a numerical iterative process, the real and imaginary parts of the CRI are retrieved using an optimal estimation method (OEM) associated to scattering theories and the single subtractive Kramers-Kronig (SSKK) relation (Herbin et al. 2017). Kaolinite, one of the main clays found in dust, has been used as a first application of this methodology. For the first time, homogenous values of CRI have been retrieved continuously from FIR to UV for suspended particles. This methodology is also being used to retrieved CRI of biomass burning aerosols (BBA). Preliminary result obtained from residual ashes will be present, showing IR extinction spectra as well as chemical analysis.
WEB POSTS
THESISAbstract This thesis argues that at least some forms of large-scale intentional modification of the climate (geoengineering) are compatible with core environmental ethics perspectives. Though environmental ethics has typically presumed against drastic alterations of the natural world, I argue that many core positions within the environmental ethics discipline do not provide grounds for a blanket rejection of geoengineering. Additionally, I argue that perspectives which do categorically reject geoengineering lack compelling reasons for acceptance. Recognising this allows environmentalists (those who would accept environmental ethics arguments) greater scope to participate in geoengineering project design; allowing them a seat at the table which they can occupy without a fundamental breach of their core ethical beliefs. I end with a discussion of principles that could govern a specifically environmentalist geoengineering.
JOB OPPORTUNITY
PODCASTS"Luke Iseman joins to talk about his project Make Sunsets, an ambitious solar geoengineering startup that aims to cool the planet by launching reflective clouds into the stratosphere.
In this episode, we chat about creating clouds, sci-fi author Neal Stephenson, living off-grid in Mexico,doomersding, spearfishing, Y Combinator, the Great Carbon Credit Tree Scam, volcano ash reflecting sunlight, wtf is solar geoengineering, how weather balloons work, reducing global temperatures, cooling credits, the difference between solarpunk and terrapunk, “propaganda of the deed”, greenwashing, combating climate doomerism, nervous scientists in ivory towers, cutting red tape, Kiribati, St. Lucia, citizenship by investment, how countries are reacting to geoengineering, NOAA, and the ethics of climate capitalism."
"Solar geoengineering — increasing the sunlight reflected back into space to cool the planet — is gaining the attention of people looking for climate solutions. But critics say it comes with risks."
YOUTUBE VIDEOSSolar Climate Intervention Virtual Symposium 10 (Dr. Ilaria Quaglia & Dr. Wake Smith) | Solar Climate Intervention Talks "Dr. Ilaria Quaglia (Cornell University, USA): "The potential of Stratospheric Aerosol Injection to reduce the climatic risks of explosive volcanic eruptions." Dr. Wake Smith (Yale University, USA): "Frosted Tips: An Alternative Rationale for Stratospheric Aerosol Injection."
E is for Earth Day, H is for Hope, B is for Books | Andrew Revkin "Three climate journalists lay out the state of the SRM sunblocking technofix, touch on methane capture and more."
Solar geoengineering: Can it solve the climate crisis? | Global News "On top of cutting down on emissions, solar geoengineering is being touted as an alternative approach to slow global warming — but it is also an unproven technology. Debate is especially growing about stratospheric aerosol injection, a type of solar geoengineering which could someday help slow the effects of climate change. Eric Sorensen explains the science, benefits and concerns of this potential solution to the climate crisis."
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