| Subscribe to our newsletter to receive monthly updates on Solar Geoengineering:
RESEARCH PAPERSHoback, A. (2024). Effectiveness of Using Calcite as an Aerosol to Remediate the Urban Heat Island. Urban Science, 8(3), 124. Abstract The purpose of this study was to develop analytical tools to find the effectiveness of using aerosols to mitigate the urban heat island effect. Specifically, mineral calcite would be placed in a plume over cities to reflect solar radiation. A secondary goal is to compare the relative efficiencies of releasing the particles from tower heights or from aircraft heights. The aim is to reduce daytime temperatures at the surface. The method was to use a one-dimensional model or a single-column model to predict temperatures and weather conditions at all altitudes over a period of one month. The SCAM6 code was altered to incorporate the new capabilities for introduced aerosols. The pre-existing code considered only windblown dust, so the code was enhanced to handle aerosols that were intentionally produced. The key findings are that calcite as an aerosol does affect the weather. The models predict that in humid regions, calcite is less effective because it interacts with water clouds. In arid regions, calcite should be more effective since there are fewer water clouds to interact with. The result is that it is possible to predict reductions in air temperatures if solar insolation can be reduced. It was shown that temperatures can be reduced by 4 °C in arid regions. The conclusions are that calcite aerosol should be effective at mitigating urban heat islands. However, further work is needed related to economic, health, and ecological concerns.
Tilmes, S., Acharya, A., Bednarz, E., & Fadnavis, S. (2024). South Asian Summer Monsoon under Stratospheric Aerosol Intervention. Abstract The South Asian summer monsoon (SAM) bears significant importance for agriculture, water resources, economy, and environmental aspects of the region for more than 1.5 billion people. To minimize the adverse impacts of global warming, Stratospheric Aerosol Intervention (SAI) has been proposed to lower surface temperatures by reflecting a portion of solar radiation back into space. However, the effects of SAI on SAM are still very uncertain and demand more research. We investigate this using the Stratospheric Aerosol Geoengineering Large Ensemble datasets. Our study reveals a reduction in the mean and extreme summer monsoon precipitation under SAI in this scenario, driven by a combination of the SAI-induced lower stratospheric warming and the associated weakening of the northern hemispheric subtropical jet, changes in the upper-tropospheric wave activities, geopotential height anomalies, and the strength of the Asian Summer Monsoon Anticyclone. Local dust changes that can otherwise be important for SAM rainfall variability under climate change also contribute to changes under SAI. As the interest in SAI research grows, our results demonstrate the urgent need to understand SAM variability under different SAI scenarios, which is essential for sustainable development and disaster preparedness in South Asia.
Jeggle, K., Neubauer, D., Binder, H., & Lohmann, U. (2024). Cirrus formation regimes–Data driven identification and quantification of mineral dust effect. EGUsphere, 2024, 1-25. Abstract The microphysical and radiative properties of cirrus clouds are strongly dependent on the ice nucleation mechanism and origin of the ice crystals. Due to sparse temporal coverage of satellite data and limited observations of ice nucleating particles (INPs) at cirrus levels it is notoriously hard to determine the origin of the ice and the nucleation mechanism of cirrus clouds in satellite observations. In this work we combine three years of satellite observations of cirrus clouds from the DARDAR-Nice retrieval product with Lagrangian trajectories of reanalysis data of meteorological and aerosol variables calculated 24 h backward in time for each observed cirrus cloud. In a first step, we identify typical cirrus cloud formation regimes by clustering the Lagrangian trajectories and characterize observed microphysical properties for in situ and liquid origin cirrus clouds in midlatitudes and the tropics. On average, in situ cirrus clouds have smaller ice water content (IWC) and lower ice crystal number concentration (Nice) and a strong negative temperature dependence of Nice, while liquid origin cirrus have a larger IWC and higher Nice and a strong positive temperature dependence of IWC. In a second step, we use MERRA2 reanalysis data to quantify the sensitivity of cirrus cloud microphysical properties to a change in the concentration of dust particles that may act as INPs. By identifying similar cirrus cloud formation pathways, we can condition on ice-origin, region, and meteorological dependencies, and quantify the impact of dust particles for different formation regimes. We find that at cloud top median Nice decreases with increasing dust concentrations for liquid origin cirrus. Specifically, the sensitivities are between 5 % and 11 % per unit increase of dust concentration in logarithmic space in the tropics and between 12 % and 18 % in the mid-latitudes. The decrease in Nice can be explained by increased heterogeneous ice nucleation in the mixed-phase regime, leading to fewer cloud droplets freezing homogeneously once the cloud enters the cirrus temperatures and glaciates. The resulting fewer, but larger ice crystals are more likely to sediment, leading to reduced IWC, as for example observed for liquid origin cirrus in the mid-latitudes. In contrast, for in situ cirrus in the tropics, we find an increase of Nice median values of 21 % per unit increase of dust aerosol in logarithmic space. We assume that this is caused by heterogeneous nucleation of ice initiated by dust INPs in INP limited conditions with supersaturations between the heterogeneous and homogeneous freezing thresholds. Such conditions frequently occur at high altitudes, especially in tropical regions at temperatures below 200 K. Our results provide an observational line of evidence that the climate intervention method of seeding cirrus clouds with potent INPs may result in an undesired positive cloud radiative effect (CRE), i.e. a warming effect. Instead of producing fewer but larger ice crystals, which would lead to the desired negative CRE, we show that additional INPs can lead to an increase in Nice, an effect called overseeding.
Alagoz, B. B., Keles, C., Ates, A., & Baran, B. (2024). A Mathematical Modelling for Solar Irradiance Reduction of Sunshades and Some Near-future Albedo Modification Approaches for Mitigation of Global Warming. Journal of Atmospheric and Solar-Terrestrial Physics, 106337. Abstract To address the global warming problem, one of the space-based geoengineering solutions suggests the construction of an occluding disc that can work as a solar curtain to mitigate solar irradiation penetration to the earth atmosphere. A widely discussed concept needs the construction of a large-scale sunshade system near the Sun–Earth L1 equilibrium point in order to control the average global temperature. However, to improve the accuracy of theoretical estimations, more consistent modeling of the Sun-Curtain-Earth system and solar irradiance reduction rate are required. This study revisits the mathematical modeling of the solar irradiance reduction system and considers the fundamentals of shading physics. Simplified mathematical modeling of solar irradiance reduction rate is derived based on the solar flux density. For the climate control, controllability of the reduction rate by using some physical parameters (e.g., flux reflection rate and angle of the curtain) is discussed. Based on the results of this model, the technical challenges and feasibility of constructing a sunshade system at L1 Lagrange point are evaluated. Some technologically feasible, near-future options for the warming problem are discussed briefly.
Morrison, A. L., Pathak, D., Barnes, E. A., & Hurrell, J. W. Projected changes to Arctic shipping routes after stratospheric aerosol deployment in the ARISE-SAI scenarios. Frontiers in Climate, 6, 1426679. Abstract Rapid reductions in Arctic sea ice in response to warming have led to increased interest in using the Arctic Ocean for commercial shipping. As the world warms, however, different strategies are being considered to stabilize or reduce surface temperatures in order to prevent critical climate change impacts. One such strategy is stratospheric aerosol injection (SAI), a form of solar climate intervention. Projected changes to Arctic sea ice under SAI with specific regards to shipping have not yet been assessed. We compare output from two SAI simulations that have different global mean temperature targets with a non-SAI control simulation to provide the first assessment of Arctic Ocean navigability under potential SAI scenarios. We find that sea ice concentration and thickness quickly stabilize or increase after SAI deployment. When sea ice thickness stabilizes in response to SAI, the number of days when the Arctic Ocean is navigable remains fairly constant, but increasing sea ice thickness leads to reduced navigability compared to the non-SAI simulation. From 2035-2069, both the Northwest Passage and Northern Sea Route are accessible from July-November in all three simulations, but there are no navigable routes under either SAI scenario from April-June. When the Arctic is navigable, it can take 2-12 days longer to cross the Arctic Ocean in the SAI simulations than in the non-SAI control simulation, and there are large year-to-year variations in travel time. Overall, Arctic shipping may take longer and be more difficult in an SAI vs a non-SAI world because of relatively thicker sea ice, but the degree to which Arctic shipping may change in response to SAI is dependent on the particular climate intervention strategy.
WEB POSTS
UPCOMING EVENTSDiscovery workshop focussing on atmospheric science (SRM) | 18 October 2024 | Online Integrative synthesis workshop focusing on identifying gaps in current governance & ethics | 18 November 2024 | Online
Solar Geoengineering Events Calendar
JOB OPPORTUNITY"The Climate Systems Engineering initiative (CSEi) at the University of Chicago invites applications for the 2025 inaugural cohort of CSEi Postdoctoral Researchers, to be appointed at the rank of Research Associate. We seek outstanding early career scholars interested in any aspect of climate engineering. The University of Chicago is building a substantial research cluster (including an anticipated ten new faculty lines) on the science, technology, and public policy of Climate Systems Engineering. Our goal is to advance understanding of the benefits, risks, and governance of technologies that might reduce the impacts of accumulated greenhouse gases, and to educate students who will face the challenges of managing industrial civilization on a fragile planet. CSEi’s topical scope includes open-system carbon removal such as enhanced weathering, solar geoengineering, and interventions to limit loss of glacial ice. CSEi welcomes research from across fields including the sciences, humanities, social sciences, public policy, and law. The CSEi Postdoctoral Researchers program aims to develop the next generation of research leaders who will shape the future of climate systems engineering for the benefit of people and the planet. CSEi Postdoctoral Researchers will work closely with UChicago faculty mentors, but their research and funding are independent, and the program will help them develop strong research networks by facilitating collaboration among the postdoctoral cohort and by ensuring that they have ample opportunities to interact with the full community of CSEi-affiliated faculty and research leaders. Securing a faculty mentor in advance is strongly preferred, and applicants are encouraged to reach out early to engage a mentor. UChicago faculty members from any discipline may potentially serve as a mentor, regardless of whether they have prior experience with climate systems engineering."
PODCASTSGeoengineering part 1: the case to try modifying the climate (The Conservation Weekly) | Geoengineering part 1: the case to try modifying the climate The Conversation Weekly 28:31 |
"Geoengineering, the modification of the climate using technological interventions to reverse climate change, is a hugely divisive issue and we’ve decided to explore it in two episodes. In this first episode, we talk to scientists working on potential geoengineering technologies who argue the case for conducting research into these interventions. We speak to Shaun Fitzgerald, director of the Centre for Climate Repair at the University of Cambridge in the UK and Hugh Hunt, deputy director at the Centre, as well as Ben Kravitz, assistant professor of Earth and atmospheric sciences at Indiana University in the US. We're also joined by Stacy Morford, environment and climate editor at The Conversation in the US."
Geoengineering part 2: the case against reflecting sunlight to cool the earth (The Conservation Weekly) | Geoengineering part 2: the case against reflecting sunlight to cool the Earth The Conversation Weekly 31:30 |
"In the second of two episodes on geoengineering, we hear the case against trying to reflect sunlight to cool the Earth. Solar radiation modification has attracted attention and investment in recent years as a way to potential reverse the effects of climate change, but it remains a controversial idea. We hear from researchers pushing a non-use agreement for solar geoengineering who explain why they believe these types of technologies are a dangerous distraction from what needs to be done to reduce fossil fuel emissions."
YOUTUBE VIDEOSScience Basics of Climate Change and SRM for African Stakeholders: ACF-DSG Workshop (August 2024) | DSG "The Alliance for Just Deliberation on Solar Geoengineering (DSG) partnered with The African Climate Foundation (ACF) for a series of virtual workshops focusing on the critical issues surrounding the growing conversation around Solar Radiation Modification (SRM), from an African perspective. While the potential impacts for SRM on temperature are clear, global, regional and local impacts on precipitation, agriculture, geopolitics, socioeconomic security and multiple other facets remain uncertain. This first workshop provided a deep dive into the scientific aspects of climate vulnerability in the southern African context, foundational knowledge around SRM approaches, and the state of the science (globally and locally). As with all of DSG’s workshops, these workshops are not advocacy-oriented but are part of our broader effort to enhance the capacity and knowledge of African stakeholders in the field of SRM in an unbiased way, ensuring that their voices are heard in global research and governance discussions. Participants engaged with experts offering various views on these climate intervention techniques and learned how and where to contribute towards building African narratives on SRM."
State of SRM Governance and Future Frameworks | DSG "The Alliance for Just Deliberation on Solar Geoengineering (DSG) partnered with The African Climate Foundation (ACF) for a series of virtual workshops focusing on the critical issues surrounding the growing conversation around Solar Radiation Modification (SRM), from an African perspective. While the potential impacts for SRM on temperature are clear, global, regional and local impacts on precipitation, agriculture, geopolitics, socioeconomic security and multiple other facets remain uncertain. The second workshop focused on understanding the state of SRM in the context of overall climate policy, SRM governance frameworks, and SRM intersections with justice and human rights dimensions, and how these relate to South African policies and governance activities."
| |
