Sandro Vattioni

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Vattioni

First Name

Sandro

ORCID

0000-0002-4099-3903

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03690 - Lohmann, Ulrike / Lohmann, Ulrike

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Publications 1 - 10 of 13

Near-future rocket launches could slow ozone recovery
Revell, Laura E.; Bannister, Michele T.; Brown, Tyler F.M.; et al. (2025)
npj Climate and Atmospheric Science
Rocket emissions thin the stratospheric ozone layer. To understand if significant ozone losses could occur as the launch industry grows, we examine two scenarios. Our 'ambitious' scenario (2040 launches/year) yields a -0.29% depletion in annual-mean, near-global total column ozone in 2030. Antarctic springtime ozone decreases by 3.9%. Our 'conservative' scenario (884 launches/year) yields -0.17% annual, near-global depletion; current licensing rates suggest this scenario may be exceeded before 2030. Ozone losses are driven by the chlorine produced from solid rocket motor propellant, and black carbon which is emitted from most propellants. The ozone layer is slowly healing from the effects of CFCs, yet global-mean ozone abundances are still 2% lower than measured prior to the onset of CFC-induced ozone depletion. Our results demonstrate that ongoing and frequent rocket launches could delay ozone recovery. Action is needed now to ensure that future growth of the launch industry and ozone protection are mutually sustainable.
Stratospheric injection of solid particles reduces side effects on circulation and climate compared to SO2 injections
Stefanetti, Fabrice; Vattioni, Sandro; Dykema, John A.; et al. (2024)
Environmental Research: Climate
Most research of stratospheric aerosol injection (SAI) for solar radiation modification has focused on injection of SO₂. However, the resulting sulfuric acid aerosols lead to considerable absorption of terrestrial infrared radiation, resulting in stratospheric warming and reduced cooling efficiency. Recent research suggests that solid particles, such as alumina, calcite or diamond, could minimize these side effects. Here we use, for the first time, the atmosphere-ocean-aerosol-chemistry-climate model SOCOLv4.0, incorporating a solid particle scheme, to assess the climatic impacts of SAI by these injection materials. For each substance, we model tropical SAI by means of constant yearly injection of solid particles, aimed to offset the warming induced by a high-GHG emission scenario over the 2020-2100 period by 1 K. We show that solid particles are more effective than sulfur at minimising stratospheric heating, and the resulting side-effects on the general atmospheric circulation, stratospheric moistening, and tropopause height change. As a result, solid particles also induce less residual warming over the arctic, resulting in greater reduction of GHG-induced polar amplification compared to sulfuric acid aerosols. Among the materials studied here, diamond is most efficient in reducing global warming per unit injection, while also minimizing side effects.
Side Effects of Sulfur-Based Geoengineering Due To Absorptivity of Sulfate Aerosols
Wunderlin, Elia; Chiodo, Gabriel; Sukhodolov, Timofei; et al. (2024)
Geophysical Research Letters
Sulfur-based stratospheric aerosol intervention (SAI) can cool the climate, but also heats the tropical lower stratosphere if done with injections at low latitudes. We explore the role of this heating in the climate response to SAI, by using mechanistic experiments that remove the effects of longwave absorption of sulfate aerosols above the tropopause. If longwave absorption by stratospheric aerosols is disabled, the heating of the tropical tropopause and most of the related side effects are strongly alleviated and the cooling per Tg-S injected is 40% bigger. Such side-effects include the poleward expansion of eddy-driven jets, acceleration of the stratospheric residual circulation, and delay of Antarctic ozone recovery. Our results add to other recent findings on SAI side effects and demonstrate that SAI scenarios with low-latitude injections of absorptive materials may result in atmospheric effects and regional climate changes that are comparable to those produced by the CO2 warming signal.
Microphysical Interactions Determine the Effectiveness of Solar Radiation Modification via Stratospheric Solid Particle Injection
Vattioni, Sandro; Käslin, Sina; Dykema, John; et al. (2024)
Geophysical Research Letters
Recent studies have suggested that stratospheric aerosol injection (SAI) of solid particles for climate intervention could reduce stratospheric warming compared to injection of SO2. However, interactions of microphysical processes, such as settling and coagulation of solid particles, with stratospheric dynamics have not been considered. Using a global chemistry-climate model with interactive solid particle microphysics, we show that agglomeration significantly reduces the backscatter efficiency per unit of injected material compared to mono-disperse particles, partly due to faster settling of the agglomerates, but mainly due to increased forward- over backscattering with increasing agglomerate size. Despite these effects, some materials substantially reduce required injection rates as well as perturbation of stratospheric winds, age of air and stratospheric warming compared to injection of SO2 SO2, with the most promising results being shown by 150 nm diamond particles. Uncertainties remain as to whether stratospheric dispersion of solid particles is feasible without formation of agglomerates.
In situ measurements of perturbations to stratospheric aerosol and modeled ozone and radiative impacts following the 2021 La Soufrière eruption
Li, Yaowei; Pedersen, Corey; Dykema, John; et al. (2023)
Atmospheric Chemistry and Physics
Stratospheric aerosols play important roles in Earth’s radiative budget and in heterogeneous chemistry. Volcanic eruptions modulate the stratospheric aerosol layer by injecting particles and particle precursors like sulfur dioxide (SO2) into the stratosphere. Beginning on 9 April 2021, La Soufrière erupted, injecting SO2 into the tropical upper troposphere and lower stratosphere, yielding a peak SO2 loading of 0.3–0.4 Tg. The resulting volcanic aerosol plumes dispersed predominately over the Northern Hemisphere (NH), as indicated by the CALIOP/CALIPSO satellite observations and model simulations. From June to August 2021 and May to July 2022, the NASA ER-2 high-altitude aircraft extensively sampled the stratospheric aerosol layer over the continental United States during the Dynamics and Chemistry of the Summer Stratosphere (DCOTSS) mission. These in situ aerosol measurements provide detailed insights into the number concentration, size distribution, and spatiotemporal variations of particles within volcanic plumes. Notably, aerosol surface area density and number density in 2021 were enhanced by a factor of 2–4 between 380–500 K potential temperature compared to the 2022 DCOTSS observations, which were minimally influenced by volcanic activity. Within the volcanic plume, the observed aerosol number density exhibited significant meridional and zonal variations, while the mode and shape of aerosol size distributions did not vary. The La Soufrière eruption led to an increase in the number concentration of small particles (<400 nm), resulting in a smaller aerosol effective diameter during the summer of 2021 compared to the baseline conditions in the summer of 2022, as observed in regular ER-2 profiles over Salina, Kansas. A similar reduction in aerosol effective diameter was not observed in ER-2 profiles over Palmdale, California, possibly due to the values that were already smaller in that region during the limited sampling period in 2022. Additionally, we modeled the eruption with the SOCOL-AERv2 aerosol–chemistry–climate model. The modeled aerosol enhancement aligned well with DCOTSS observations, although the direct comparison was complicated by issues related to the model’s background aerosol burden. This study indicates that the La Soufrière eruption contributed approximately 0.6 % to Arctic and Antarctic ozone column depletion in both 2021 and 2022, which is well within the range of natural variability. The modeled top-of-atmosphere 1-year global average radiative forcing was −0.08 W m−2 clear-sky and −0.04 W m−2 all-sky. The radiative effects were concentrated in the tropics and NH midlatitudes and diminished to near-baseline levels after 1 year.
An interactive stratospheric aerosol model intercomparison of solar geoengineering by stratospheric injection of SO2 or accumulation-mode sulfuric acid aerosols
Weisenstein, Debra K.; Visioni, Daniele; Franke, Henning; et al. (2022)
Atmospheric Chemistry and Physics
Studies of stratospheric solar geoengineering have tended to focus on modification of the sulfuric acid aerosol layer, and almost all climate model experiments that mechanistically increase the sulfuric acid aerosol burden assume injection of SO2. A key finding from these model studies is that the radiative forcing would increase sublinearly with increasing SO2 injection because most of the added sulfur increases the mass of existing particles, resulting in shorter aerosol residence times and aerosols that are above the optimal size for scattering. Injection of SO3 or H2SO4 from an aircraft in stratospheric flight is expected to produce particles predominantly in the accumulation-mode size range following microphysical processing within an expanding plume, and such injection may result in a smaller average stratospheric particle size, allowing a given injection of sulfur to produce more radiative forcing. We report the first multi-model intercomparison to evaluate this approach, which we label AM-H2SO4 injection. A coordinated multi-model experiment designed to represent this SO3- or H2SO4-driven geoengineering scenario was carried out with three interactive stratospheric aerosol microphysics models: the National Center for Atmospheric Research (NCAR) Community Earth System Model (CESM2) with the Whole Atmosphere Community Climate Model (WACCM) atmospheric configuration, the Max-Planck Institute's middle atmosphere version of ECHAM5 with the HAM microphysical module (MAECHAM5-HAM) and ETH's SOlar Climate Ozone Links with AER microphysics (SOCOL-AER) coordinated as a test-bed experiment within the Geoengineering Model Intercomparison Project (GeoMIP). The intercomparison explores how the injection of new accumulation-mode particles changes the large-scale particle size distribution and thus the overall radiative and dynamical response to stratospheric sulfur injection. Each model used the same injection scenarios testing AM-H2SO4 and SO2 injections at 5 and 25 Tg(S) yr−1 to test linearity and climate response sensitivity. All three models find that AM-H2SO4 injection increases the radiative efficacy, defined as the radiative forcing per unit of sulfur injected, relative to SO2 injection. Increased radiative efficacy means that when compared to the use of SO2 to produce the same radiative forcing, AM-H2SO4 emissions would reduce side effects of sulfuric acid aerosol geoengineering that are proportional to mass burden. The model studies were carried out with two different idealized geographical distributions of injection mass representing deployment scenarios with different objectives, one designed to force mainly the midlatitudes by injecting into two grid points at 30∘ N and 30∘ S, and the other designed to maximize aerosol residence time by injecting uniformly in the region between 30∘ S and 30∘ N. Analysis of aerosol size distributions in the perturbed stratosphere of the models shows that particle sizes evolve differently in response to concentrated versus dispersed injections depending on the form of the injected sulfur (SO2 gas or AM-H2SO4 particulate) and suggests that prior model results for concentrated injection of SO2 may be strongly dependent on model resolution. Differences among models arise from differences in aerosol formulation and differences in model dynamics, factors whose interplay cannot be easily untangled by this intercomparison.
Chemical and climatic impacts of solid particles for stratospheric solar climate intervention
Vattioni, Sandro (2024)
The increasingly dismal prospects for climate change mitigation are driving research on stratospheric aerosol injection (SAI), i.e., the injection of aerosols or their precursors into the stratosphere with the aim of increasing the Earth’s albedo to cool the global climate. SAI aims to quickly mitigate some of the adverse effects of climate change at low cost. The idea arose mainly from observations of the cooling effect of explosive volcanic eruptions, which explains why research on SAI has so far focused on the emission of SO₂, the main precursor of volcanic sulfuric acid aerosols in the stratosphere. However, SAI by means of sulfuric acid aerosols could lead to a number of negative side effects such as impacts on the ozone layer and stratospheric heating, and sizable effects on the large scale atmospheric circulation. A recent model intercomparison of chemistry-climate models with interactive stratospheric H₂SO₄/H₂O aerosol has revealed large uncertainties in how the microphysical aerosol processes are implemented. In particular, it was shown that compared to shortduration volcanic SO₂ emission, the continuous SO₂ injections in climate intervention scenarios can pose a greater challenge to the numerical implementation of microphysical processes such as nucleation, condensation, and coagulation. This thesis shows how simply changing the timesteps and the sequencing of microphysical processes in the sectional aerosol-chemistry-climate model SOCOL-AERv2 can result in globally averaged radiative forcing ranging from -2.3 to -5.3 W/m2 when 25 Mt/yr SO₂ is injected. This is mostly a result of a too long microphysical timestep in combination with the strong non-linearity of aerosol nucleation to H₂SO₄ supersaturation. Taken together these results underscore how structural aspects of model representation of aerosol microphysical processes become important under conditions of elevated stratospheric sulfur in determining atmospheric chemistry and climate impacts. Recent studies also suggest that the injection of solid particles such as calcite or alumina particles could lead to more effective cooling per aerosol burden compared to SAI via sulfuric acid aerosols. At the same time, solid particles could reduce some of the negative side effects such as ozone depletion or stratospheric heating due to their better optical, chemical and microphysical properties. However, this thesis shows that some of these studies relied on highly simplified aerosol model approaches or nonphysical assumptions on heterogeneous chemistry. Through experimental laboratory work and climate modeling, this thesis presents a holistic assessment of SAI using calcite and alumina particles and their uncertainties compared to SAI using sulfuric acid aerosols. Calcite particles have been proposed as potential injection candidates for SAI since they can react with acidic gases in the stratosphere (i.e., HCl, HNO₃ and H₂SO₄). Removal of HCl can lead to faster healing of the ozone layer. Conversely, strong removal of HNO3 could also result in enhanced ozone depletion due to decreased deactivation of chlorine. This work used in situ X-ray photoelectron spectroscopy (XPS) and elastic recoil detection analysis (ERDA) to measure the uptake of HNO₃ and HCl on calcite under near-stratospheric conditions, and determined their penetration into deeper layers below the surface and the subsequent chemical transformation of calcite into calcium chlorides and nitrates. Uptake coefficients ranging from γHNO₃ = 10⁻⁵ to 10⁻⁴ were measured for HNO₃ with XPS and ranging from γHNO₃, HCl = 10⁻⁶ to 10⁻⁵ for both HNO₃ and HCl measured with ERDA. Putting these results into context of SAI, the uptake of HCl and HNO₃ decreases with stratospheric exposure time due to the formation of product layers at the surface and subsequent limitation of the uptake by slow ion diffusion. The measurements indicate that exposure of these particles to typically 5 ppb HNO₃ and 1 ppb HCl over stratospheric residence times of about 1 year leads to mean uptake coefficients < 10⁻⁴ , which represents a strong constraint to the uptake. Owing to the limited gas uptakes, the effects of calcite SAI on ozone may be much smaller than previously thought. To investigate this in more detail, this work has developed an interactive microphysical scheme for solid particles and integrated it into the aerosol-chemistry climate-model SOCOL-AERv2 and the Earth System Model SOCOLv4. These models make it possible to investigate the risks and benefits of SAI of solid particles. The solid particles considered in these models are fully interactive with the stratospheric sulfur cycle via the models’ microphysical scheme. The models allow for uptake of sulfuric acid at the particle surface via coagulation with sulfuric acid aerosols and condensation of H₂SO₄(g) on the particle surfaces, as well as the formation of solid particle agglomerates via coagulation of solid particles. Furthermore, the solid particles are subject to advection, sedimentation and interactive wet and dry deposition in the troposphere. Most importantly, the models represent the interaction of the solid particles with the radiative transfer code of the model. Finally, they include the heterogeneous chemistry on the particle surface. The modular design of the models allows switching on and off the coupling of individual processes, which enables them to investigate the sensitivity and importance of the different processes relevant for the assessment of risks and benefits of SAI by means of solid particles. Using these models, we show that SAI with alumina and calcite particles achieves a larger effective radiative forcing (RF) compared to sulfuric acid aerosols only if the same aerosol burden is maintained, but not when referring to the same unit of injected mass. Reduced warming of the tropical lower stratosphere remains a major advantage of SAI of alumina and calcite particles over SO₂ injections, as well as reduced ozone depletion and reduced diffuse radiation. However, the effects on stratospheric composition are highly uncertain, as they largely depend on the assumptions made regarding the heterogeneous chemistry on the solid particles. The extremely limited availability of experimental studies on heterogeneous chemistry on alumina under the influence of stratospheric concentrations of HCl, HNO₃, H₂SO₄, and H₂O leads to large uncertainties in the impact of alumina injection on stratospheric ozone. In order to quantify these uncertainties, we integrated the currently available knowledge about the most important heterogeneous reaction ClONO₂ + HCl surf→ Cl₂ + HNO₃ into SOCOL-AERv2. The uncertainty in the resulting heterogeneous reaction rate is more than two orders of magnitude depending on the partitioning of HCl, H₂SO₄ and HNO₃ on the alumina surface. This could lead to global ozone column depletion ranging between almost negligible and up to 9%, which would be more than twice as much as the ozone loss caused by chlorofluorocarbons in the late 1990s. Given the current level of scientific understanding, sulfur-based SAI appears to have smaller uncertainties than solid particles, and could therefore be considered potentially safer. Conversely, SAI using solid particles has more potential for reduced side effects but also greater uncertainties. To constrain this structural uncertainty in models, both dedicated laboratory experiments as well as small scale field experiments will be required.
A fully coupled solid-particle microphysics scheme for stratospheric aerosol injections within the aerosol-chemistry-climate model SOCOL-AERv2
Vattioni, Sandro; Weber, Rahel; Feinberg, Aryeh; et al. (2024)
Geoscientific Model Development
Recent studies have suggested that injection of solid particles such as alumina and calcite particles for stratospheric aerosol injection (SAI) instead of sulfur-based injections could reduce some of the adverse side effects of SAI such as ozone depletion and stratospheric heating. Here, we present a version of the global aerosol–chemistry–climate model SOCOL-AERv2 and the Earth system model (ESM) SOCOLv4 which incorporate a solid-particle microphysics scheme for assessment of SAI of solid particles. Microphysical interactions of the solid particle with the stratospheric sulfur cycle were interactively coupled to the heterogeneous chemistry scheme and the radiative transfer code (RTC) for the first time within an ESM. Therefore, the model allows simulation of heterogeneous chemistry at the particle surface as well as feedbacks between microphysics, chemistry, radiation and climate. We show that sulfur-based SAI results in a doubling of the stratospheric aerosol burden compared to the same mass injection rate of calcite and alumina particles with a radius of 240 nm. Most of the sulfuric acid aerosol mass resulting from SO2 injection does not need to be lifted to the stratosphere but is formed after in situ oxidation and subsequent water uptake in the stratosphere. Therefore, to achieve the same radiative forcing, larger injection rates are needed for calcite and alumina particle injection than for sulfur-based SAI. The stratospheric sulfur cycle would be significantly perturbed, with a reduction in stratospheric sulfuric acid burden by 53 %, when injecting 5 Mt yr⁻¹ (megatons per year) of alumina or calcite particles of 240 nm radius. We show that alumina particles will acquire a sulfuric acid coating equivalent to about 10 nm thickness if the sulfuric acid is equally distributed over the whole available particle surface area in the lower stratosphere. However, due to the steep contact angle of sulfuric acid on alumina particles, the sulfuric acid coating would likely not cover the entire alumina surface, which would result in available surface for heterogeneous reactions other than the ones on sulfuric acid. When applying realistic uptake coefficients of 1.0, 10⁻⁵ and 10⁻⁴ for H₂SO₄, HCl and HNO₃, respectively, the same scenario with injections of calcite particles results in 94 % of the particle mass remaining in the form of CaCO₃. This likely keeps the optical properties of the calcite particles intact but could significantly alter the heterogeneous reactions occurring on the particle surfaces. The major process uncertainties of solid-particle SAI are (1) the solid-particle microphysics in the injection plume and degree of agglomeration of solid particles on the sub-ESM grid scale, (2) the scattering properties of the resulting agglomerates, (3) heterogeneous chemistry on the particle surface, and (4) aerosol–cloud interactions. These uncertainties can only be addressed with extensive, coordinated experimental and modelling research efforts. The model presented in this work offers a useful tool for sensitivity studies and incorporating new experimental results on SAI of solid particles.
Chemical Impact of Stratospheric Alumina Particle Injection for Solar Radiation Modification and Related Uncertainties
Vattioni, Sandro; Luo, Beiping; Feinberg, Aryeh; et al. (2023)
Geophysical Research Letters
Compared to stratospheric SO2 injection for climate intervention, alumina particle injection could reduce stratospheric warming and associated adverse impacts. However, heterogeneous chemistry on alumina particles, especially chlorine activation via ${\text{ClONO}}_{2}+\text{HCl}\stackrel{\text{surf}}{\to }{\text{Cl}}_{2}+{\text{HNO}}_{3}$, is poorly constrained under stratospheric conditions, such as low temperature and humidity. This study quantifies the uncertainty in modeling the ozone response to alumina injection. We show that extrapolating the limited experimental data for ClONO2 + HCl to stratospheric conditions leads to uncertainties in heterogeneous reaction rates of almost two orders of magnitude. Implementation of injection of 5 Mt/yr of particles with 240 nm radius in an aerosol-chemistry-climate model shows that resulting global total ozone depletions range between negligible and as large as 9%, that is more than twice the loss caused by chlorofluorocarbons, depending on assumptions on the degree of dissociation and interaction of the acids HCl, HNO3, and H2SO4 on the alumina surface.
Analysis of the global atmospheric background sulfur budget in a multi-model framework
Brodowsky, Christina V.; Sukhodolov, Timofei; Chiodo, Gabriel; et al. (2024)
Atmospheric Chemistry and Physics
A growing number of general circulation models are adapting interactive sulfur and aerosol schemes to improve the representation of relevant physical and chemical processes and associated feedbacks. They are motivated by investigations of climate response to major volcanic eruptions and potential solar geoengineering scenarios. However, uncertainties in these schemes are not well constrained. Stratospheric sulfate is modulated by emissions of sulfur-containing species of anthropogenic and natural origin, including volcanic activity. While the effects of volcanic eruptions have been studied in the framework of global model intercomparisons, the background conditions of the sulfur cycle have not been addressed in such a way. Here, we fill this gap by analyzing

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