Stratospheric aerosol geoengineering

 

2, upper left panel). The most well-researched SRM methodology is stratospheric aerosol injection (SAI), which involves increasing the concentration of aerosol particles in the stratosphere to reduce the amount of solar radiation reaching Earth’s surface. The last decade has seen broad exploratory research into stratospheric aerosol (SA) geoengineering, motivated by concern that reducing greenhouse gas emissions may be insufficient to avoid significant impacts from climate change. Another limitation was that in their warming scenarioonlyCO 2 concentrationschange Solar geoengineering, by adding aerosols to the stratosphere that reflect some sunlight, could be used to partially offset the climate change from increased carbon dioxide (CO 2). J. The Geoengineering Model Intercomparison Project, conducting climate model experiments with standard stratospheric aerosol injection scenarios, found that insolation has reduction could keep the global average temperature constant, but global average precipitation would reduce, particularly in summer monsoon regions around the world. $. Mar 20, 2020 · The effects of stratospheric aerosol geoengineering necessarily depend on how it would be deployed, particularly on choices about the spatial distribution and magnitude of the radiative forcing (Keith 2013, Kravitz et al 2016). Sep 11, 2019 · Research examines the possibility of spraying tiny particles into the stratosphere to block the sun a bit and cool the planet. For very large increases in stratospheric aerosol burden (4. We conclude by arguing that, while cheap, such an aircraft-based program Stratospheric aerosol injection is a commonly discussed geoengineering concept based on the idea that adding particles to the stratosphere could help cool the surface of the planet by reflecting Abstract Stratospheric aerosol geoengineering has been proposed as a potential solution to reduce climate change and its impacts. The reduction in mean precipitation expected for solar geoengineering is less important than the temperature-driven shift from solid to liquid precipitation for forcing Dec 15, 2021 · The climate simulation datasets from the Stratospheric Aerosol Geoengineering Large Ensemble (GLENS) Project dataset (Tilmes et al. , 1998). Stratospheric aerosol injection (SAI, also called stratospheric particle injection, SPI) is one of the bolder and more controversial methods of solar radiation management. We lay out a future solar geoengineering deployment scenario of halving the increase in anthropogenic radiative forcing beginning 15 years hence, by deploying material to altitudes as high as ~20 km. 2 Mt of SO2 in year 1 and ramp up linearly thereafter at 0. Yet physical risks and efficacy of stratospheric aerosol Nov 6, 2017 · An important question to address regarding solar geoengineering with stratospheric aerosols is the best estimate for the projected climate effects. Apr 4, 2019 · Abstract: We review the capabilities and costs of various lofting methods intended to deliver sulfates into the lower stratosphere. 17. , 2008; Stenchikov et al. 2018) were analysed for the study. Based on this research, it is plausible that a limited deployment of SA geoengineering, provided it is Solar geoengineering There are several proposed solar geoengineering technologies. Aug 17, 2023 · The geoengineering technique of solar geoengineering or solar radiation management (SRM) might be able to help (for more on geoengineering techniques, see here [5]). 8% compared to the representative concentration pathway 4. Jun 9, 2020 · By reflecting some incoming solar radiation, stratospheric aerosol intervention using SO 2 would reduce global mean temperature. We investigate the impacts of stratospheric aerosol injection (SAI) geoengineering on summer (June-August, JJA) temperature and precipitation over East Asia as well as the East Asian summer monsoon (EASM) by using model outputs archived in the G4 stratospheric aerosol injection Feb 23, 2024 · The numbers in the figure are the r-values of the stratospheric aerosol burden with tropical average (20°N and 20°S) stratospheric winds at 50 hPa (axis on the right) per each decade, with sulfate burden on the left and wind strength on the right, (b) the standard deviation of the global stratospheric aerosol burden divided by the mean values Dec 3, 2019 · Stratospheric aerosol geoengineering, by releasing sulfate aerosol particles or their precursors (SO 2) into the stratosphere to scatter more sunlight back to space, is a potential climate intervention option to counteract anthropogenic global warming. Because the Arctic receives little sunlight during the winter, stratospheric aerosols present in the winter at high latitudes have little impact on the climate, whereas Rutgers University May 1, 2008 · A technological, societal, or political crisis could halt a project of stratospheric aerosol injection in mid-deployment. Oct 2, 2013 · Most geoengineering technologies generally either reflect sunlight — through artificial ‘clouds’ of stratospheric aerosols, for example — or reduce the amount of greenhouse gases in the May 20, 2021 · The researchers found that all three potential solar geoengineering methods have a strong cooling effect that would benefit crop yields. Dec 21, 2022 · Solar radiation management (SRM) is a climate engineering strategy to reduce temperature increases due to global climate change. While climate simulations provide evidence that the long-term result of SAI could lead to stabilized global temperatures ( 17 ), the impacts of SAI may be regionally heterogeneous, with temperature stratospheric aerosol geoengineering. Apr 14, 2013 · Deliberating stratospheric aerosols for climate geoengineering and the SPICE project. Jan 31, 2011 · However, Robock et al. , 2017). This means that the cooling effect of stratospheric aerosol geoengineering would persist for many months after termination. Mar 29, 2021 · Stratospheric aerosol injection would make the sun’s light more diffuse, which could affect ecosystems, farms, and solar electricity installations. The decision to implement such a scheme would require a comparison of its benefits, dangers, and costs to those of other responses to global warming, including doing nothing. Because the radiative damping timescales are longer in the lower stratosphere than in the Mar 11, 2018 · From observations of the stratospheric aerosol burden following large volcanic eruptions, an e-folding time of roughly one year has been calculated (Robock et al. Here, we explore the responses of the Hadley circulation (HC) intensity and the intertropical convergence zone (ITCZ) using the strategic stratospheric aerosol geoengineering, in which sulfur dioxide was injected into the stratosphere at four different locations to Stratospheric aerosol geoengineering, by releasing sulfate aerosol particles or their precursors (SO 2) into the stratosphere to scatter more sunlight back to space, is a potential climate intervention option to counteract anthropogenic global warming. Such Nov 1, 2021 · As a potential approach to counteract global warming, geoengineering has attracted much attention in recent years. The deliberate injection of aerosols into the stratosphere is a solar-radiation management (SRM) scheme Mar 15, 2020 · It includes the Geoengineering Model Inter-comparison Project (GeoMIP), in which 19 climate modeling groups have simulated how the climate would respond to reduced insolation, creation of a stratospheric aerosol cloud, or brightened marine clouds to reduce climate change from various global warming scenarios. This proposal for ‘‘solar radiation management,’’ to reduce inso-lation with an anthropogenic stratospheric aerosol cloud in the same manner as episodic explosive volcanic eruptions, willbecalled‘‘geoengineering’’here,recognizingthatothers The Geoengineering Model Intercomparison Project, conducting climate model experiments with standard stratospheric aerosol injection scenarios, has found that insolation reduction could keep the global average temperature constant, but global average precipitation would reduce, particularly in summer monsoon regions around the world. May 22, 2023 · The Geoengineering Large Ensemble (GLENS, Tilmes et al. Earth system model (ESM) simulations confirm expectations from physical principles, that climate system thermodynamics will change when a reduction in shortwave (SW) radiative flux is designed to offset increases in longwave (LW Feb 28, 2023 · There is growing interest from scientists, governments and philanthropists in researching stratospheric aerosol injection, a form of solar radiation management, or SRM (Climatewire, Feb. Total pre-start costs to launch a hypothetical SAI effort 15 years from now are $3. Stratospheric aerosol geoengineering (SAI) seeks to mimic the effects of volcanic eruptions that inject sulfur compounds into the lower stratosphere11. But could the cure be worse than the disease? Understanding low probability, yet plausible, high-impact cases is critical to prudent climate risk management and SAI deliberation. 11. Apr 14, 2013 · Accordingly, acceptance of the test bed should not be misconstrued as unconditional acceptance of, or support for, either stratospheric aerosols or geoengineering more generally but rather a Nov 19, 2021 · Injecting particles into atmosphere to reflect sunlight, stratospheric aerosol injection (SAI), represents a potential technological solution to the threat of climate change. SCoPEx was designed to measure the stratospheric behavior of aerosols in plumes to advance scientific knowledge relevant to potential future implementation of solar geoengineering. Stratospheric aerosol injection (SAI) is the SRM strategy of releasing particles into the stratosphere to slow, pause, or reverse global warming . However, the climate impacts of such intervention are unclear. Abstract: Stratospheric aerosol geoengineering is a proposal to artificially thicken the layer of reflective aerosols in the stratosphere and it is hoped that this may offer a means of reducing average climate changes. Mar 30, 2022 · The Stratospheric Aerosol GLENS project is a 20-member ensemble of stratospheric sulfate aerosol geoengineering simulations between 2020 and 2099 and a 20-member ensemble of CRTL simulations over a reference period between 2010 and 2030 using the NCAR Community Earth System Model with the Whole Atmosphere Community Climate Model (WACCM) as its Dec 14, 2019 · Stratospheric aerosol injection (SAI) with sulfate aerosols is the most commonly simulated geoengineering proposal. 5 K, and slows down the global hydrological cycle. We further calculate the number of flights at ∼4000 in year one, linearly increasing by ∼4000 yr −1. Unlike for a reduction in solar constant, stratospheric aerosols absorb radiation as well as scatter it, producing a warming of the lower stratosphere that has important impacts on regional hydroclimate (Simpson et al 2019). The warming effect of greenhouse gases is Oct 13, 2022 · The White House is coordinating a five-year research plan to study ways of modifying the amount of sunlight that reaches the earth to temper the effects of global warming, a process sometimes Oct 2, 2009 · [1] Injecting sulfate aerosol precursors into the stratosphere has been suggested as a means of geoengineering to cool the planet and reduce global warming. Additionally, if we were to suddenly stop deploying stratospheric aerosols after relying on it for significant cooling, the rapid rebound to warmer temperatures could cause extreme weather or ecological changes. Stratospheric aerosol geoengineering cannot perfectly offset the effects of climate change. The climate effects depend on the spatial distribution of aerosols within the stratosphere, which is at least partially a design choice enabled by choosing how much mass to inject at multiple Mar 25, 2024 · Studies have shown that enhancements of the stratospheric sulfate aerosol layer from SAI would increase the aerosol surface area density, influencing halogen activation in the lower stratosphere and the removal of active nitrogen species in the middle stratosphere, thereby modulating chemical ozone loss (Bednarz et al. , season), and even what (the composition of the aerosols). There's no going back. Therefore, geoengineering by means of sulfate aerosols is predicted to accelerate the hydroxyl catalyzed ozone destruction cycles and cause a significant depletion of the ozone layer even Mar 18, 2024 · An Update on SCoPEx Monday, March 18, 2024 The Stratospheric Controlled Perturbation Experiment (SCoPEx) is a scientific effort initiated by Professors David Keith and Frank Keutsch at Harvard University. 122, 12616–12634 (2017). Geophys. Major volcanic eruptions have been used as natural analogues to large-scale deployments of stratospheric aerosol geoengineering, yet difference in climate responses to these forcings remains unclear. The large burden of sulfate aerosols injected into the stratosphere by the eruption of Mount Pinatubo in 1991 cooled Earth and enhanced the destruction of polar ozone in the subsequent few years. . 3±0. Atmos. Previous studies focused on the effect of aerosol injection on annual mean climate change. In this study, we use Geoengineering Model Intercomparison Project G4 experiment simulations from six models that counteract anthropogenic forcing under medium–low emissions Apr 11, 2021 · Stratospheric aerosol geoengineering focused on the Arctic could substantially reduce local and worldwide impacts of anthropogenic global warming. Abstract Stratospheric aerosol geoengineering focused on the Arctic could substantially reduce local and worldwide impacts of anthropogenic global warming. In this study, we compare two SAI simulations which inject at different altitudes to provide the same amount of cooling, finding that lower-altitude SAI requires 64% more injection. Mar 18, 2024 · The Stratospheric Controlled Perturbation Experiment (SCoPEx) is a scientific effort initiated by Professors David Keith and Frank Keutsch at Harvard University. Increasing concerns about the narrowing Nov 23, 2018 · We calculate early-year costs of ∼$1500 ton −1 of material deployed, resulting in average costs of ∼$2. 2 Mt SO2/yr would require average annual operating costs of $2. , 2023a, 2023b; Haywood et Jun 14, 2022 · Abstract. 27). Nov 1, 2018 · Abstract This paper describes the Stratospheric Aerosol Geoengineering Large Ensemble (GLENS) project, which promotes the use of a unique model dataset, performed with the Community Earth System Model, with the Whole Atmosphere Community Climate Model as its atmospheric component [CESM1(WACCM)], to investigate global and regional impacts of geoengineering. decreases with increasing stratospheric aerosol burden (Fig. The warming effect of greenhouse gases is Nov 3, 2023 · Abstract. ∼. , 2018a) and Assessing Responses and Impacts of Solar climate intervention on the Earth system with stratospheric aerosols (ARISE-SAI-1. These include marine cloud brightening, cirrus cloud thinning, space-based techniques, and stratospheric aerosol scattering, amongst others. Photo: ISS/NASA A new study finds that injecting SO 2 at higher latitudes, rather than in the tropics, could mitigate some undesirable side effects of SAI – but all options come with trade-offs. Here we use the state-of-the-art Community Earth System Model, version 1, with the Whole Atmosphere Community Climate Model as its atmospheric component (CESM1(WACCM)), to compare surface climate and stratospheric effects of two geoengineering strategies. Mar 11, 2019 · The most promising and affordable of these methods is stratospheric aerosol injection, which involves spewing tiny particles into the upper atmosphere. A program that would deploy 0. However, different choices for the aerosol injection latitude(s) and season(s) have been shown to lead to significant differences in We find stratospheric sulfate aerosol injection geoengineering, G3, can slow shrinkage of high-mountain Asia glaciers by about 50 % by 2069 relative to losses from RCP8. There would also be complex effects on Oct 29, 2018 · First simulations of designing stratospheric sulfate aerosol geoengineering to meet multiple simultaneous climate objectives. Crossref Jun 18, 2019 · Geoengineering with stratospheric sulfate aerosols can, to some extent, be designed to achieve different climate objectives. Despite offsetting global mean surface temperature, various studies demonstrated that stratospheric aerosol injection (SAI) could influence the recovery of stratospheric ozone and have important impacts on stratospheric and tropospheric circulation, thereby potentially playing an important role in modulating regional and seasonal climate variability. Res. Those particles would reflect sunlight May 30, 2024 · Stratospheric aerosol injection (SAI) is one of the widely studied methods of solar geoengineering 3, 4, 5, 6, which aims to reflect solar radiation by injecting aerosols or their precursors Apr 11, 2021 · Stratospheric aerosol geoengineering focused on the Arctic could substantially reduce local and worldwide impacts of anthropogenic global warming. Adding aerosols to the lower stratosphere would result in temporary global cooling. Previous research has shown that multiple injection latitudes can be used to maintain not only global mean temperature, but also interhemispheric and equator-to-pole temperature gradients. Jan 22, 2019 · Abstract. Stratospheric aerosol injection (SAI) may prevent tipping points that lead to widespread permafrost thaw and carbon release by cooling surface and soil temperatures, but it is unclear if or when permafrost could stabilize after SAI deployment. Solar radiation modification ( SRM ), or solar geoengineering, is a type of climate engineering (or geoengineering) in which sunlight ( solar radiation) would be reflected back to outer space to offset human-caused global warming. 3 of supplementary material). Jul 20, 2023 · Stratospheric aerosol injection (SAI) of reflective sulfate aerosols has been proposed to temporarily reduce the impacts of global warming. Based on this research, it is plausible that a limited deployment of SA geoengineering, provided it is used in Here, we test if this result holds for a more realistic representation of stratospheric aerosol geoengineering using the data from the geoengineering large ensemble (GLENS). Nick Pidgeon1*, Karen Parkhill1, Adam Corner1 and Naomi Vaughan2. The simulated stratospheric aerosol burdens show a weak dependence on the latitudinal spread of emissions. Chapter 24 in Resilience: The Science of Adaptation to Climate Change, Keith Alverson and Zinta Zommers, editors, (Elsevier, Amsterdam), 292-304, ISBN: 978-0-12-811891-7. There are multiple potential approaches, with stratospheric aerosol injection being the most-studied, followed by Mar 30, 2015 · The Geoengineering Model Intercomparison Project, conducting climate model experiments with standard stratospheric aerosol injection scenarios, has found that insolation reduction could keep the global average temperature constant, but global average precipitation would reduce, particularly in summer monsoon regions around the world. Jan 27, 2014 · Our simulations show that geoengineering injection of stratospheric aerosol can lead to dramatic changes in the QBO, prolonging the phase of easterly shear with respect to the control simulation. However, so far, most of the Jan 25, 2022 · Abstract. In recent years NCAR's state-of-the-art Whole Atmosphere Community Climate Model (WACCM) has been developed to include interactive coupling between aerosols, chemistry, radiation, and Oct 12, 2023 · Stratospheric aerosol injection (SAI) has been proposed as a possible response option to limit global warming and its societal consequences. 25 billion yr −1 over the first 15 years of deployment. J Geophys Res Atmos 122 , 12574–12590 (2017). Stratospheric aerosol intervention (SAI) geoengineering is a proposed scheme to counteract anthropogenic global warming, but the climate response to SAI, with great regional disparities, remains uncertain. Aug 21, 2020 · By injecting at 15°N, 30°N, 15°S, and 30°S in the Geoengineering Large Ensemble simulations performed with the Community Earth System Model (CESM1(WACCM)), it was possible to produce a stratospheric aerosol layer capable of reducing global mean temperatures over the course of the 21st century as well as restoring the inter-hemispheric and Apr 6, 2024 · Permafrost, or ground that is continuously frozen for at least 2 years, contains vast stores of organic soil carbon. Aug 12, 2012 · Many strategies and techniques for geoengineering Earth's climate have been suggested 1,2. 5. One is to simply reduce insolation (the solar radiation that reaches the Earth’s surface), which is easily implemented in a climate model by reducing the solar constant, or reducing insolation in certain re-gions. Jun 16, 2023 · Sulfate aerosols would also fall back to Earth as acid rain once they complete their lifespan in the stratosphere. 36 W m −2, reduces mean global temperature by ∼0. Stratospheric aerosol injection (SAI), as a possible supplement to emission reduction, has the potential to reduce some of the risks associated with climate change. Nov 8, 2018 · G4 stratospheric aerosol geoengineering lowers net radiation fluxes at the TOA by ∼0. 5 % per kelvin in response to G4 stratospheric aerosol injection (Ji et al. When sulfur dioxide enters the atmosphere, it reacts with water vapor to form droplets—aerosols that reflect sunlight away from Earth. , Corey Gabriel, Alan Robock, and Lili Xia, 2018: Ecological, agricultural and health impacts of solar geoengineering. 25 billion yr over 15 years. Using a linearized scaling of GLENS we find that halving warming with stratospheric aerosols moderates important climate hazards in almost all regions. Such an abrupt shift would result in rapid climate warming, which would produce much more stress on society and ecosystems than gradual global warming. Abstract: Injecting sulfate aerosol into the stratosphere, the most frequently analyzed proposal for solar geoengineering, may reduce some climate risks, but it would also entail new risks, including ozone loss and heating of the lower tropical stratosphere, which, in turn, would increase water vapor concentration causing additional ozone loss Apr 24, 2024 · After Mount Pinatubo in the Philippines erupted in 1991, sending 20 million tons of sulfur dioxide into the stratosphere, the Earth cooled by 0. Apr 5, 2024 · Under Stratospheric Aerosol Injection, the Arctic land with temperatures permanently below freezing decreased by 7. Oct 25, 2016 · A decision to deploy a geoengineering intervention is not binary: in the case of stratospheric aerosols, one can choose not only how much aerosol to add but also where (e. , latitude), when (e. Sep 13, 2019 · Since the spatial pattern of aerosol optical depth can be at least partially controlled, stratospheric aerosol geoengineering using multiple injection locations can improve how well geoengineering compensates for the spatial pattern of climate changes due to increased atmospheric CO 2 concentrations (MacMartin et al. Eight engineers and chemists give updates on their preceding day’s work: ordering parts, transferring software, untangling an administrative snafu. Previous research suggested that cooling temperatures brought on by stratospheric aerosol injection may also lead to less rainfall, which could result in yield loss for rainfed crops. point out that stratospheric geoengineering with sulphate aerosols could have unintended and possibly harmful consequences, including potential impacts on the hydrologic cycle and ozone depletion. Because the Arctic receives little sunlight during the winter, stratospheric aerosols present in the winter at high latitudes have little impact on the climate, whereas stratospheric aerosols present May 18, 2022 · Solar geoengineering, in particular stratospheric aerosol injection (SAI), has been debated as a possible intervention method to reduce some of the worst effects of global warming. The GLENS datasets were generated with the Community Earth System Model (CESM1), which uses the Whole Atmosphere Community Climate Model (WACCM) as its atmospheric component On average, the stratospheric aerosol burden and corresponding all-sky shortwave radiative forcing for the AM H 2 SO 4 scenarios are about 37 % larger than for the SO 2 scenarios. g. We provide an overview of geoengineering by stratospheric sulphate aerosols. The most considered and heavily Mar 30, 2015 · The Geoengineering Model Intercomparison Project, conducting climate model experiments with standard stratospheric aerosol injection scenarios, has found that insolation reduction could keep the global average temperature constant, but global average precipitation would reduce, particularly in summer monsoon regions around the world. For policymakers to be able to make informed decisions, the strength and patterns of these climate system responses need to be Aug 5, 2019 · Solar geoengineering has been suggested as a potential means to counteract anthropogenic warming. May 15, 2020 · Geoengineering, defined as the deliberate large-scale manipulation of earth’s energy balance to mitigate global warming 10, may present a viable proposition for stabilizing carbon storage in circum-Arctic permafrost. The performed simulations were Jan 7, 2019 · The climate response to stratospheric aerosol geoengineering can be tailored using multiple injection locations. Nov 6, 2023 · Stratospheric aerosol injection mimics the effect of a volcano by pumping gas into the sky that turns into aerosols, reflecting part of the sun's heat. SAI would recreate Pinatubo’s effect by shooting sulfur Dec 15, 2020 · The deliberate introduction of aerosols into the stratosphere as a means of solar geoengineering (SG) might reduce some climate risks. Global precipitation decreases by 2. Marine cloud brightening would attempt to brighten marine clouds to reflect more sunlight back into space. stratospheric geoengineering using sulfate aerosols. Here, we explore the responses of the Hadley circulation (HC) intensity and Jan 23, 2019 · The Stratospheric Aerosol Geoengineering Large Ensemble project is a 20-member ensemble of stratospheric sulfate aerosol geoengineering simulations between 2020-2099 and a 20-member ensemble of control simulations over a reference period between 2010-2030 using the NCAR Community Earth System Model with the Whole Atmosphere Community Climate Model as its atmospheric component (CESM1 WACCM Stratospheric geoengineering has been implemented in GCM studies mainly in two different ways. Every morning, the Keutsch Research Group gathers for a meeting. But analyses of such high impact outcomes May 15, 2020 · Stratospheric aerosol geoengineering (SAI) seeks to mimic the effects of volcanic eruptions that inject sulfur compounds into the lower stratosphere 11. , 2018). 5, Richter et al. Feb 15, 2024 · Abstract Stratospheric aerosol geoengineering has been proposed as a potential solution to reduce climate change and its impacts. Here, we explore the responses of the Hadley circulation (HC) intensity and the intertropical convergence zone (ITCZ) using the strategic stratospheric aerosol geoengineering, in which sulfur dioxide was injected into the stratosphere at four different locations to Trisos, Christopher H. 522-25km u z RT yy /H. , 2022) projects are the first large ensembles of Earth system model simulations that comprehensively represent processes most important Oct 1, 2023 · If stratospheric aerosols were used to offset the average warming caused by a quadrupling of CO 2 levels, the tropics would be 0. The heating from the geoengineering aerosol induces a warming of the lower stratosphere up to about 27 km altitude (Fig. 7 Tg-S), the lower tropical stratosphere is locked into a permanent westerly QBO phase. However, one of the concerns is that this does not affect the climate the same way that increased CO 2 does, leading to some regions cooling more than others. Feb 5, 2024 · Debates about this idea, a form of solar geoengineering called stratospheric aerosol injection (SAI), commonly focus either on small-scale outdoor research that seeks to understand the physical Apr 19, 2022 · Stratospheric aerosol geoengineering has been proposed as a potential solution to reduce climate change and its impacts. Comprehensive Earth System Models are required that represent the most important processes essential to simulate different potential geoengineering proposals. In 2019, the University established an external Apr 2, 2024 · The term refers to activities like stratospheric aerosol injections, an untested theory that the planet could be cooled by spraying particles into the stratosphere from high-altitude aircraft. 5˚ C. The continuous injection of sulfur into the stratosphere has been suggested as a “geoengineering” scheme to counteract global warming. More importantly, the sedimenting particles heat the tropical cold point tropopause and, hence, the stratospheric entry mixing ratio of H 2 O increases. 5 billion in 2018 US. 3 degree C cooler than in preindustrial times, but the polar The G4 stratospheric aerosol geoengineering was relatively less effective in increasing cold spell duration and decreasing warm spell duration in equatorial oceans than G1 solar dimming geoengineering, consistent with a relatively smaller cooling effect in coldest day and warmest night in equatorial oceans than in adjacent regions. The state of understanding about this topic as of early 2008 is reviewed, summarizing the past 30 years of work in the area, highlighting some very recent studies using climate models, and discussing methods used to deliver sulphur species to the stratosphere. Stratospheric aerosol geoengineering (SAI) seeks to mimic the effects of volcanic eruptions that inject sulfur compounds into May 30, 2008 · Abstract. tp ml by oq oa fs cc gp ik ft