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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. [ABSTRACT FROM AUTHOR]

Beijing is undergoing multiple challenges including urbanization, warming and aging. The Beijing megalopolis of 20 million people now suffers more cold‐related than heat‐related deaths. Stratospheric aerosol injection (SAI) geoengineering is designed to lower surface temperatures, so if SAI were ever done, it may reduce future heat‐related mortality, while also increasing cold‐related mortality. Here we use four Earth System Models (ESM) downscaled to 10 km resolution with the Weather Research and Forecasting (WRF) system to capture urban temperature, humidity and wind speeds. Temperature‐related mortality risk were calculated using a distributed lag nonlinear model (DLNM) of the elderly (over 65s) under the dynamically downscaled moderate (RCP4.5) and extreme (RCP8.5) greenhouse gas, and the G4 SAI scenarios. We used population demographics for all five shared socioeconomic pathways (SSP) and various adaptation measures. Heat‐related excess deaths under G4 are 630∼3,160 per year fewer than RCP4.5, while cold‐related deaths are 370∼1,990 more than RCP4.5 during 2060–2069, with a marginally significant net reduction. G4 significantly reduces the excess deaths relative to RCP8.5. Both heat‐related and cold‐related mortality will increase by 240∼490% when the aging population is accounted for, and decrease by 11%, 23% and 44% under low, medium and high adaptation relative to a no adaptation scenario. Dynamical downscaling produces better quality climate simulations than commonly used statistical approaches, and in the case of Beijing, significantly fewer heat‐related deaths. The marginal health benefits of modest future SAI in Beijing may be representative of the population impacts in the extra‐tropics where deaths due to cold are more than those caused by heat. Plain Language Summary: Climate warming has increased the intensity and frequency of extreme weather has consequences for human health in the 21st century. Stratospheric aerosol injection (SAI) geoengineering can, to some extent, slow down global warming, but its impact on human health is unclear. Beijing is one of the most populous and developed cities in China and is undergoing dual challenges of warming and aging which amplify the health risks to the elderly population. It is therefore of both local significance and wider relevance for developing world cities to explore the impact of SAI geoengineering on the mortality of elderly people in Beijing. We project heat‐related and cold‐related excess deaths under different climate, population and adaptation scenarios in Beijing during the 2060s. SAI geoengineering could reduce approximately 630∼3,160 heat‐related excess deaths, but it could also increase 370∼1,990 cold‐related excess deaths. There are large uncertainties in projection of excess deaths under different shared socioeconomic pathways. Key Points: Stratospheric aerosol injection (SAI) geoengineering on both heat‐related and cold‐related mortality for the elderly in Beijing was simulatedGeoMIP G4 SAI reduces heat‐related excess deaths, but also increases cold‐related excess deaths, with little net negative differences from RCP4.5Dynamical downscaling significantly reduces projecting future heat‐related excess deaths relative to statistical methods [ABSTRACT FROM AUTHOR]

Heat transported in Circumpolar Deep Water is driving the break‐up of ice shelves in the Amundsen Sea sector of Antarctica, that has been simulated to be unavoidable under all plausible greenhouse gas scenarios. However, Solar geoengineering scenarios remain largely unexplored. Solar geoengineering changes global thermal radiative balance, and atmospheric and oceanic transportation pathways. We simulate stratospheric aerosol injection (SAI) designed to reduce global mean temperatures from those under the unmitigated SSP5‐8.5 scenario to those under the SSP2‐4.5 scenario with six CMIP6‐class Earth System Models. These consistently show intensified Antarctic polar vortex and sub‐polar westerlies, which mitigates changes to easterly winds along the Amundsen Sea continental shelf compared with greenhouse gas scenarios. The models show significantly cooler Amundsen Sea waters and lower heat content at 300–600 m under SAI than with either solar dimming or the SSP5‐8.5 unmitigated greenhouse gas scenarios. However, the heat content increases under all scenarios compared with present day suggesting that although vulnerable ice shelves would continue to thin, the rate would be lower for SAI even with SSP5‐8.5 specified greenhouse gases, than for the moderate (SSP2‐4.5) scenario. The simulations here use solar geoengineering designed to meet global temperature targets; interventions targeted at preserving the frozen high latitudes have also been proposed that might be expected to produce bigger local effects, but potentially deleterious impacts elsewhere. Considering the huge disruptions to society of ice sheet collapse, more research on avoiding them by intervention technology is a moral imperative. Plain Language Summary: The Amundsen Sea sector of Antarctica is important because major ice sheet outlet glaciers are at, or close to, the tipping point threshold when greenhouse gas concentrations become irrelevant to their fate. Multi‐meter sea level rises are essentially inevitable once past this tipping point, forcing hundreds of millions of people to relocate (mainly in the Global South), and costing around $40 billion per year per meter of sea level rise through the rest of the century in coastal defense systems. Hence any methods that may avoid ice sheet collapse should be researched. In this article we use 6 state of the art earth system models to simulate putting aerosols into the stratosphere (mimicking volcanic eruptions), might affect the heat carried by the oceans to the vulnerable glaciers in the Amundsen Sea. The stratospheric aerosols change the winds that drive warm deep water toward the glaciers, lowering the expected melting compared with the no greenhouse gas mitigation scenario, and even the lowered emissions pledged by the international community. This result contrasts with earlier work suggesting the ice sheets were doomed and encourages more sophisticated climate system interventions scenarios targeted toward to high latitudes. Key Points: We simulate the effect of stratospheric aerosol injection (SAI) and greenhouse gas scenarios on ocean heat flow in the Amundsen SeaSAI impacts stratospheric winds that propagate into ocean circulation changes that reduce heat flow to the ice edgeResearching ideas, that can complement mitigation, may provide alternatives to avoid crossing damaging social tipping points [ABSTRACT FROM AUTHOR]

The frozen elements of the high North are thawing as the region warms much faster than the global mean. The dangers of sea level rise due to melting glacier ice, increased concentrations of greenhouse gases from thawing permafrost, and alterations in the key high latitude physical systems spurred many authors, and more recently international agencies and supra-state actors, to investigate “emergency measures” that might help conserve the frozen North. However, the efficacy and feasibility of many of these ideas remains highly uncertain, and some might come with significant risks, or could be even outright dangerous to the ecosystems and people of the North. To date, no review has evaluated all suggested schemes. The objectives of this first phase literature survey (which can be found in a separate compendium (), are to consider all proposed interventions in a common evaluation space, and identify knowledge gaps in active conservation proposals. We found 61 interventions with a high latitude focus, across atmosphere, land, oceans, ice and industry domains. We grade them on a simple three-point evaluation system across 12 different categories. From this initial review we can identify which ideas scored low marks on most categories and are therefore likely not worthwhile pursuing; some groups of interventions, like traditional land-based mitigation efforts, score relatively highly while ocean-based and sea ice measures, score lower and have higher uncertainties overall. This review will provide the basis for a further in-depth expert assessment that will form phase two of the project over the next few years sponsored by University of the Arctic. [ABSTRACT FROM AUTHOR]

Some argue that complementing climate change mitigation measures with solar radiation management (SRM) might prove a last resort to limit global warming to 1.5 °C. To make a socially responsible decision on whether to use SRM, it is important to consider also public opinion, across the globe and particularly in the Global South, which would face the greatest risks from both global warming and SRM. However, most research on public opinion about SRM stems from the Global North. We report findings from the first large-scale, cross-cultural study on the public opinion about SRM among the general public (N = 2,248) and students (N = 4,583) in 20 countries covering all inhabited continents, including five countries from the Global South and five ‘non-WEIRD’ (i.e. not Western, Educated, Industrialised, Rich, and Democratic) countries from the Global North. As public awareness of SRM is usually low, we provided participants with information on SRM, including key arguments in favour of and against SRM that appear in the scientific debate. On average, acceptability of SRM was significantly higher in the Global South than in the ‘non-WEIRD’ Global North, while acceptability in the ‘WEIRD’ Global North was in between. However, we found substantial variation within these clusters, especially in the ‘non-WEIRD’ Global North, suggesting that countries do not form homogenous clusters and should thus be considered individually. Moreover, the average participants’ views, while generally neither strong nor polarised, differed from some expert views in important ways, including that participants perceived SRM as only slightly effective in limiting global warming. Still, our data suggests overall a conditional, reluctant acceptance. That is, while on average, people think SRM would have mostly negative consequences, they may still be willing to tolerate it as a potential last resort to fight global warming, particularly if they think SRM has only minor negative (or even positive) impacts on humans and nature. [ABSTRACT FROM AUTHOR]

Abstract Beijing is undergoing multiple challenges including urbanization, warming and aging. The Beijing megalopolis of 20 million people now suffers more cold‐related than heat‐related deaths. Stratospheric aerosol injection (SAI) geoengineering is designed to lower surface temperatures, so if SAI were ever done, it may reduce future heat‐related mortality, while also increasing cold‐related mortality. Here we use four Earth System Models (ESM) downscaled to 10 km resolution with the Weather Research and Forecasting (WRF) system to capture urban temperature, humidity and wind speeds. Temperature‐related mortality risk were calculated using a distributed lag nonlinear model (DLNM) of the elderly (over 65s) under the dynamically downscaled moderate (RCP4.5) and extreme (RCP8.5) greenhouse gas, and the G4 SAI scenarios. We used population demographics for all five shared socioeconomic pathways (SSP) and various adaptation measures. Heat‐related excess deaths under G4 are 630∼3,160 per year fewer than RCP4.5, while cold‐related deaths are 370∼1,990 more than RCP4.5 during 2060–2069, with a marginally significant net reduction. G4 significantly reduces the excess deaths relative to RCP8.5. Both heat‐related and cold‐related mortality will increase by 240∼490% when the aging population is accounted for, and decrease by 11%, 23% and 44% under low, medium and high adaptation relative to a no adaptation scenario. Dynamical downscaling produces better quality climate simulations than commonly used statistical approaches, and in the case of Beijing, significantly fewer heat‐related deaths. The marginal health benefits of modest future SAI in Beijing may be representative of the population impacts in the extra‐tropics where deaths due to cold are more than those caused by heat.

Abstract Heat transported in Circumpolar Deep Water is driving the break‐up of ice shelves in the Amundsen Sea sector of Antarctica, that has been simulated to be unavoidable under all plausible greenhouse gas scenarios. However, Solar geoengineering scenarios remain largely unexplored. Solar geoengineering changes global thermal radiative balance, and atmospheric and oceanic transportation pathways. We simulate stratospheric aerosol injection (SAI) designed to reduce global mean temperatures from those under the unmitigated SSP5‐8.5 scenario to those under the SSP2‐4.5 scenario with six CMIP6‐class Earth System Models. These consistently show intensified Antarctic polar vortex and sub‐polar westerlies, which mitigates changes to easterly winds along the Amundsen Sea continental shelf compared with greenhouse gas scenarios. The models show significantly cooler Amundsen Sea waters and lower heat content at 300–600 m under SAI than with either solar dimming or the SSP5‐8.5 unmitigated greenhouse gas scenarios. However, the heat content increases under all scenarios compared with present day suggesting that although vulnerable ice shelves would continue to thin, the rate would be lower for SAI even with SSP5‐8.5 specified greenhouse gases, than for the moderate (SSP2‐4.5) scenario. The simulations here use solar geoengineering designed to meet global temperature targets; interventions targeted at preserving the frozen high latitudes have also been proposed that might be expected to produce bigger local effects, but potentially deleterious impacts elsewhere. Considering the huge disruptions to society of ice sheet collapse, more research on avoiding them by intervention technology is a moral imperative.

The term “climate engineering” is an ambiguous label for two categories of technologies for mediating global warming, Carbon Dioxide Removal (CDR) and Solar Radiation Modification (SRM). Whether CDR and SRM should be grouped together under a common umbrella term, or whether they should be treated as two disparate problems in need of disparate solutions, has long been a matter of debate. This paper first provides an empirical analysis of disaggregation. Topic modelling the scientific literature on climate engineering, I highlight a trend towards disaggregation driven by growth in the specialized literature on CDR. Second, I explore inconsistencies in the theoretical rationale for disaggregation and challenges in its practical implications. Third, I elaborate on the theoretical and practical utility of maintaining an integrated concept of climate engineering for highlighting the challenges of governing large-scale, hypothetical technological interventions into the climate system subject to deep uncertainties and mitigation deterrence.

Ocean iron fertilization (OIF) aims to remove carbon dioxide (CO2) from the atmosphere by stimulating phytoplankton carbon‐fixation and subsequent deep ocean carbon sequestration in iron‐limited oceanic regions. Transdisciplinary assessments of OIF have revealed overwhelming challenges around the detection and verification of carbon sequestration and wide‐ranging environmental side‐effects, thereby dampening enthusiasm for OIF. Here, we utilize five requirements that strongly influence whether OIF can lead to atmospheric CO2 removal (CDR): The requirement (a) to use preformed nutrients from the lower overturning circulation cell; (b) for prevailing iron‐limitation; (c) for sufficient underwater light for photosynthesis; (d) for efficient carbon sequestration; (e) for sufficient air‐sea CO2 transfer. We systematically evaluate these requirements using observational, experimental, and numerical data in an "informed back‐of‐the‐envelope approach" to generate circumpolar maps of OIF (cost‐)efficiency south of 60°S. Results suggest that (cost‐)efficient CDR is restricted to locations on the Antarctic Shelf. Here, CDR costs can be <100 US$/tonne CO2 while they are mainly >>1,000 US$/tonne CO2 in offshore regions of the Southern Ocean, where mesoscale OIF experiments have previously been conducted. However, sensitivity analyses underscore that (cost‐)efficiency is in all cases associated with large variability and are thus difficult to predict, which reflects our insufficient understanding of the relevant biogeochemical and physical processes. While OIF implementation on Antarctic shelves appears most (cost‐)efficient, it raises legal questions because regions close to Antarctica fall under three overlapping layers of international law. Furthermore, the constraints set by (cost‐)efficiency reduce the area suitable for OIF, thereby likely reducing its maximum CDR potential. Key Points: Iron fertilization efficiency is constrained mainly by carbon transfer efficiency into Antarctic Bottom Water and air‐sea CO2 exchangeIron fertilization could cost below 100 US‐Dollar per tonne CO2 on Antarctic shelves but may be much more expensive off shelves(Cost‐)efficient Iron Fertilization is restricted to relatively small parts of the Southern Ocean that are protected by international law [ABSTRACT FROM AUTHOR]

Under global warming scenarios, extreme climate events in South Asia will occur more frequently which will seriously threaten the safety of local residents. South Asia faces dual pressures of the obligation of carbon emissions reduction globally and the demand for a better life for huge populations. Stratospheric Aerosol Injection (SAI) climate engineering provides a potential solution to this dilemma. We compared the evolution of 12 climate extreme indices under historical scenarios, two future scenarios (SSP245, SSP585) and an implementation scenario of SAI climate engineering (G6sulfur). We showed that the intensity and frequency of extreme climates under a G6sulfur scenario would be significantly higher than those under historical scenarios, and that the difference in extreme climates under three scenarios (SSP245, SSP585, and G6sulfur) would be widely varying, with some indices being considerably mitigated while others would reflect a worse set of circumstances than would be the case without SAI climate engineering. Therefore, SAI climate engineering is not an effective tool to mitigate future climate extremes in South Asia under global warming scenarios. [ABSTRACT FROM AUTHOR]

Meteorological hazards can lead farmers to resort to strategies such as weather modifications. In this paper, we study how the use of such strategies, in this case silver iodide ground generators aimed at protecting vineyards from hail, caused a conflict between farmers (wine producers and cattle breeders) in Burgundy, France. The conflict emerged as the installation of these generators coincided with 3 years of severe droughts (2018, 2019 and 2020), which incurred additional expenses and organisational difficulties for local cattle breeders and led them to suspect a potential link between the generators and the droughts. We followed a transdisciplinary research approach, based on local stakeholder input and their need to mitigate the negative impacts of the conflict. Based on this approach, we studied the links between generator use and precipitation, and carried out in-depth interviews to study farmers’ experiences of climate, generators and conflicts in the region. Whilst the climatic analysis shows no local or regional effects of the generators on precipitation volumes, the sociological study highlights the vulnerability of farmers to successive droughts, found to be part of a wider pattern of climate change based on water balance variables (temperature, precipitation, evapotranspiration potential, soil wetness index) over a long period (1959–2020). Our results suggest that the use of technical solutions to mitigate meteorological hazards, within a broader context of climate engineering, can lead to conflicts at the regional level, and that the climate change challenge in the context of agriculture requires a focus on wider social issues including vulnerability. [ABSTRACT FROM AUTHOR]

Global air temperatures continue to rise despite efforts to curb greenhouse gas emissions. Supplementary technological interventions may become necessary to avoid harmful consequences resulting from unabated temperature increases. One such intervention involves the artificial reduction of incoming solar radiation through the release of reflective particles into the stratosphere: stratospheric aerosol injection (SAI). The American public is generally unfamiliar with SAI, despite increasing media coverage. We conducted a content analysis of frames in US news focused on SAI between 2014 and 2022 to identify and catalogue the most prominent dimensions that are employed in news coverage. We then use these dimensions to design a two-wave survey experiment evaluating how combinations of positive and negative frames that appear in recent journalistic accounts affect the American public’s beliefs about SAI and support for research. The results demonstrate how exposure to framed communications can exert a powerful and durable impact on the public’s beliefs and general support for SAI. [ABSTRACT FROM AUTHOR]

Deliberations are underway to utilize increasingly radical technological options to help address climate change and stabilize the climatic system. Collectively, these options are often referred to as "climate geoengineering." Deployment of such options, however, can create wicked tradeoffs in governance and require adaptive forms of risk management. In this study, we utilize a large and novel set of qualitative expert interview data to more deeply and systematically explore the types of risk–risk tradeoffs that may emerge from the use of 20 different climate geoengineering options, 10 that focus on carbon dioxide or greenhouse gas removal, and 10 that focus on solar radiation management and reflecting sunlight. We specifically consider: What risks does the deployment of these options entail? What types of tradeoffs may emerge through their deployment? We apply a framework that clusters risk–risk tradeoffs into institutional and governance, technological and environmental, and behavioral and temporal dimensions. In doing so, we offer a more complete inventory of risk–risk tradeoffs than those currently available within the respective risk‐assessment, energy‐systems, and climate‐change literatures, and we also point the way toward future research gaps concerning policy, deployment, and risk management. [ABSTRACT FROM AUTHOR]

Climate change poses grave risks to food security, and mitigation and adaptation actions have so far been insufficient to lessen the risk of climate-induced violations of the right to food. Could safeguarding the right to food, then, justify some forms of geoengineering? This article examines geoengineering through the analytical lens of the right to food. We look at the components of food security and consider how the acceptability of geoengineering relates to the right to food via its impacts on these components. Our examination shows that results vary greatly between different forms of geoengineering: while some forms of geoengineering fail to respect the right to food, certain other forms may even become obligatory to protect the right to food. It appears that there is no support for aerosol-based solar radiation management, whereas some carbon dioxide removal methods can help protect or promote the right to food. The ethical challenges related to carbon dioxide removal methods are, we note, similar to those that will also be faced in the course of climate change mitigation. [ABSTRACT FROM AUTHOR]

Stratospheric aerosol injection (SAI) would involve the addition of sulfate aerosols in the stratosphere to reflect part of the incoming solar radiation, thereby cooling the climate. Studies trying to explore the impacts of SAI have often focused on idealized scenarios without explicitly introducing what we call ‘inconsistencies’ in a deployment. A concern often discussed is what would happen to the climate system after an abrupt termination of its deployment, whether inadvertent or deliberate. However, there is a much wider range of plausible inconsistencies in deployment than termination that should be evaluated to better understand associated risks. In this work, we simulate a few representative inconsistencies in a pre-existing SAI scenario: an abrupt termination, a decade-long gradual phase-out, and 1 year and 2 year temporary interruptions of deployment. After examining their climate impacts, we use these simulations to train an emulator, and use this to project global mean temperature response for a broader set of inconsistencies in deployment. Our work highlights the capacity of a finite set of explicitly simulated scenarios that include inconsistencies to inform an emulator that is capable of expanding the space of scenarios that one might want to explore far more quickly and efficiently.

Negative emissions technologies and solar radiation management techniques could contribute towards climate stability, either by removing carbon dioxide from the atmosphere and storing it permanently or reflecting sunlight away from the atmosphere. Despite concerns about them, such options are increasingly being discussed as crucial complements to traditional climate change mitigation and adaptation. Expectations around negative emissions and solar radiation management and their associated risks and costs shape public and private discussions of how society deals with the climate crisis. In this study, we rely on a large expert survey (N = 74) to critically examine the future potential of both negative emission options (e.g., carbon dioxide removal) and solar radiation management techniques. We designed a survey process that asked a pool of prominent experts questions about (i) the necessity of adopting negative emissions or solar radiation management options, (ii) the desirability of such options when ranked against each other, (iii) estimations of future efficacy in terms of temperature reductions achieved or gigatons of carbon removed, (iv) expectations about future scaling, commercialization, and deployment targets, and (v) potential risks and barriers. Unlike other elicitation processes where experts are more positive or have high expectations about novel options, our results are more critical and cautionary. We find that some options (notably afforestation and reforestation, ecosystem restoration, and soil carbon sequestration) are envisioned frequently as necessary, desirable, feasible, and affordable, with minimal risks and barriers (compared to other options). This contrasts with other options envisaged as unnecessary risky or costly, notably ocean alkalization or fertilization, space-based reflectors, high-altitude sunshades, and albedo management via clouds. Moreover, only the options of afforestation and reforestation and soil carbon sequestration are expected to be widely deployed before 2035, which raise very real concerns about climate and energy policy in the near- to mid-term. [ABSTRACT FROM AUTHOR]

Under global warming scenarios, extreme climate events in South Asia will occur more frequently which will seriously threaten the safety of local residents. South Asia faces dual pressures of the obligation of carbon emissions reduction globally and the demand for a better life for huge populations. Stratospheric Aerosol Injection (SAI) climate engineering provides a potential solution to this dilemma. We compared the evolution of 12 climate extreme indices under historical scenarios, two future scenarios (SSP245, SSP585) and an implementation scenario of SAI climate engineering (G6sulfur). We showed that the intensity and frequency of extreme climates under a G6sulfur scenario would be significantly higher than those under historical scenarios, and that the difference in extreme climates under three scenarios (SSP245, SSP585, and G6sulfur) would be widely varying, with some indices being considerably mitigated while others would reflect a worse set of circumstances than would be the case without SAI climate engineering. Therefore, SAI climate engineering is not an effective tool to mitigate future climate extremes in South Asia under global warming scenarios.

Climate change is worsening cyclone disaster risk. Current risk reduction responses focus on reducing vulnerability and exposure. However, these approaches are not keeping up with climate change. Intervening in the cyclone hazard itself has the potential to prevent deaths and destruction, and reduce the costs of disaster recovery. We provide a technical review of these interventions. This unifies an otherwise sparse and disconnected literature, providing a starting point for further discussion by academics and policymakers. Potential interventions include cloud seeding, using pipes to inject cool water into cyclone hotspots, injecting particles into the upper atmosphere and atmospheric aerosol injections. Approaches have different logistical requirements, side effects and promise. Understanding the effectiveness and associated risks of different interventions will inform prudent cyclone risk management and research. Our review points to the promise of aerosol injection and high-altitude particle injection as first research directions. We also discuss potential governance risks and requirements of cyclone interventions. Cyclone interventions raise many issues, ranging from robust monitoring of ecological side effects, to geopolitics and politicisation. Current international climate governance is ill-suited for potential technologies on the horizon. Good decision-making is required to maximise benefits and reduce negative impacts. Cyclone interventions could be a potentially transformative response to climate change, and should be a priority for future research.

The impacts of global climate change on international security and geopolitics could be of historic proportion, challenging those of previous global threats such as nuclear weapons proliferation, the Great Depression, and terrorism. But while the evidence surrounding the security impacts of climate change is fairly well-understood and improving, less is known about the security risks to climate-technology deployment. In this study, we focus on the geopolitical, security, and military risks facing negative emissions and solar geoengineering options. Although controversial, these options could become the future backbone of a low-carbon or net-zero society, given that they avoid the need for coordinated or global action (and can be deployed by a smaller group of actors, even non-state actors), and that they can “buy time” for mitigation and other options to be scaled up. We utilize a large and diverse expert-interview exercise (N = 125) to critically examine the security risks associated with ten negative emission options (or greenhouse gas removal technologies) and ten solar geoengineering options (or solar radiation management technologies). We ask: What geopolitical considerations does deployment give rise to? What particular military applications exist? What risks do these options entail in terms of weaponization, misuse, and miscalculation? We examine such existing and prospective security risks across a novel conceptual framework envisioning their use as (i) diplomatic or military negotiating tools, (ii) objectives for building capacity, control, or deterrence, (iii) targets in ongoing conflicts, and (iv) causes of new conflicts. This enables us to capture a far broader spectrum of security concerns than those which exist in the extant literature and to go well beyond insights derived from climate modelling or game theory by drawing on a novel, rich, and original dataset of expert perceptions.

Since the early 2000s, proposals to deliberately modify the Earth's climate have gained political traction as a controversial last resort measure against dangerous global warming. The article provides a 'longue durée' picture of such climate engineering proposals. It traces their historical trajectory from the late 1950s to their most recent arrival on mainstream climate policy agendas. This perspective suggests that the history of climate engineering unfolds not only along historically specific modes of understanding climatic change. It also corresponds to changing alliances between climate science and the state. By bringing together historical scholarship with contributions from sociology and science policy studies, the article sheds new light on the rise of climate engineering proposals. It recontextualizes these proposals within the bigger history of the political cultivation of climate science. This perspective highlights how deeply entwined efforts to understand and efforts to govern climatic change have always been. This article is categorized under:Climate, History, Society, Culture > Ideas and KnowledgeThe Social Status of Climate Change Knowledge > Sociology/Anthropology of Climate KnowledgeThe Social Status of Climate Change Knowledge > Knowledge and Practice [ABSTRACT FROM AUTHOR]

Making informed future decisions about solar radiation modification (SRM; also known as solar geoengineering)--approaches such as stratospheric aerosol injection (SAI) that would cool the climate by reflecting sunlight--requires projections of the climate response and associated human and ecosystem impacts. These projections, in turn, will rely on simulations with global climate models. As with climate-change projections, these simulations need to adequately span a range of possible futures, describing different choices, such as start date and temperature target, as well as risks, such as termination or interruptions. SRMmodeling simulations to date typically consider only a single scenario, often with some unrealistic or arbitrarily chosen elements (such as starting deployment in 2020), and have often been chosen based on scientific rather than policy-relevant considerations (e.g., choosing quite substantial cooling specifically to achieve a bigger response). This limits the ability to compare risks both between SRM and non-SRM scenarios and between different SRM scenarios. To address this gap, we begin by outlining some general considerations on scenario design for SRM. We then describe a specific set of scenarios to capture a range of possible policy choices and uncertainties and present corresponding SAI simulations intended for broad community use. [ABSTRACT FROM AUTHOR]

In ethical reflections on new technologies, a specific type of argument often pops up, which criticizes scientists for "playing God" with these new technological possibilities. The first part of this article is an examination of how these arguments have been interpreted in the literature. Subsequently, this article aims to reinterpret these arguments as symbolic arguments: they are grounded not so much in a set of ontological or empirical claims, but concern symbolic classificatory schemes that ground our value judgments in the first place. Invoking symbolic arguments thus refers to how certain new technologies risk undermining our fundamental symbolic distinctions by which we organize and evaluate our interactions with the world and in society. Such symbolic distinctions, moreover, tend to be resilient against logical argumentation, mainly because they themselves form the basis on which we argue in the cultural and ethical sphere in the first place. Therefore, effective strategies to evaluate and counter these arguments require another approach, showing that these technologies either do not challenge these classifications or, if they do, how they can be accompanied by the proper actions to integrate these technologies into our society. [ABSTRACT FROM AUTHOR]

Researchers disagree on the extent that brief survey methods accurately reflect citizens' opinions of unfamiliar scientific concepts. We examine whether encouraging participants to engage in more reflective thinking affects their perceptions of emerging climate technologies. Drawing on dual-process theories of reasoning, we apply experimental manipulations to encourage fast, intuitive thinking or slow, reflective thinking when responding to an online survey. Similarities in concept evaluation time between the Control and the Intuitive treatment groups indicates that citizens default to fast intuitive judgements to form opinions. However, despite a successful manipulation check, the reflective treatment group did not show any substantively different results. Therefore, encouraging additional thinking is unlikely to shift public perceptions. Post hoc analysis suggests participants with stronger views may nonetheless take more time to consider their response, without prompting. These findings support the validity of surveys as a method for eliciting stable and meaningful public perceptions of emerging technologies. [ABSTRACT FROM AUTHOR]

Solar geoengineering is gaining prominence in climate change debates as an issue worth studying; for some it is even a potential future policy option. We argue here against this increasing normalization of solar geoengineering as a speculative part of the climate policy portfolio. We contend, in particular, that solar geoengineering at planetary scale is not governable in a globally inclusive and just manner within the current international political system. We therefore call upon governments and the United Nations to take immediate and effective political control over the development of solar geoengineering technologies. Specifically, we advocate for an International Non‐Use Agreement on Solar Geoengineering and outline the core elements of this proposal. This article is categorized under:Policy and Governance > International Policy Framework [ABSTRACT FROM AUTHOR]

Calls for moratoria are a frequent response to controversial issues in international diplomacy and control of technology, and are now prominent in debates over governance challenges posed by climate engineering (CE) – intentional modification of the global climate to reduce changes caused by human emissions of greenhouse gases. Based on twelve historical cases of moratoria in other areas of diplomatic conflict or controversial science and technology, we present a novel analytic framework to examine purposes, design characteristics, and conditions for effectiveness of moratoria, based on a taxonomy of three ideal moratorium types: risk-management moratoria, principled-conflict moratoria, and bargaining moratoria. We use this framework to examine potential contributions and design conditions for a moratorium on CE. A moratorium for CE could seek primarily to advance risk-management aims or bargaining aims, with distinct implications for its timing, scope, associated actors, and conditions for termination. Beyond the current, high-stakes case of CE, the proposed analytic framework has broader implications for critical examination of moratorium proposals, current and future, in other areas of controversial research, technology, and governance challenges.

The Anthropocene is giving rise to novel challenges for global environmental governance. The barriers and opportunities shaping the ways in which some of these complex environmental challenges become governable on the global level are of increasing academic and practical relevance. In this article, we bring neo-institutionalist and post-structuralist perspectives together in an innovative framework to analyse how both institutional and discursive structures together bound and shape the global governance opportunities which become thinkable and practicable in the face of new global environmental challenges. We apply this framework to explore how governance of climate engineering – large scale, deliberate invention into the global climate system – is being shaped by discursive and institutional structures in three international forums: The London Convention and its Protocol, the Convention on Biological Diversity, and the United Nations Environment Assembly. We illustrate that the 'degree of fit' between discursive and institutional structures made climate engineering (un)governable in each of these forums. Furthermore, we find that the ' type of fit' set the discursive and institutional conditions of possibility for what type of governance emerged in each of these cases. Based on our findings, we critically discuss the implications for the future governance of climate engineering at the global level. • Climate engineering presents a novel challenge for global environmental governance • Institutional and discursive structures co-shape global environmental governance • A lack of joint analyses of both structures impedes understanding of governance emergence • A joint neo-institutionalist and post-structuralist analysis addresses this gap • Varying structures shape differing climate engineering governance decisions in several forums [ABSTRACT FROM AUTHOR]

The most recent IPCC report considers Carbon Dioxide Removal (CDR) as an unavoidable climate change mitigation measure, although controversial discussions about CDR have taken place in the past. This study contributes to the ongoing debate by providing insights into academic expert opinions about Bioenergy with Carbon Capture and Storage (BECCS) and Direct Air Carbon Capture and Storage (DACCS). An online survey was conducted to examine how academic experts ( N = 172) perceive and to what extent they support BECCS and DACCS. Overall, the results show rather high expert support for research on and the deployment of BECCS and DACCS. Perceived feasibility of the technologies consistently predicted support for BECCS and DACCS, with means in the upper medium range. Further significant predictors were the extent to which experts perceived the technologies to be necessary, the experts’ amount of academic experience, the associated moral hazard, and the perceived tampering with nature.

In recent years, the idea of geoengineering, understood as large‐scale interventions in the planet's climate to counteract anthropogenic climate change, has steadily increased its visibility. Presented explicitly as an approach to climate change, geoengineering is positioned as a response, a reactive fix. Geoengineering, however, has a longer and broader history than the current climate crisis. It has long been an umbrella term for large‐scale projects in which various Earth sciences meet dreams about human ecosphere interventions, especially regarding lithosphere and climate and weather modifications. In this paper, we review the history of geoengineering, focusing specifically on climate geoengineering and lithosphere geoengineering. We draw attention to the difference between "proactive" ("high‐modernist"), aimed at mastery over nature, and "reactive" forms of geoengineering, hoping to address anthropogenic environmental degradation technologically. Additionally, we trace historical (dis)continuities between the older, proactive, form of geoengineering and their recent reframing as a technological fix—specifically around the question to what extent nature's complex systems can be known and controlled. Finally, we argue for the need to further research the intersections and shared histories between various forms of geoengineering. This article is categorized under:Climate, History, Society, Culture > Ideas and Knowledge [ABSTRACT FROM AUTHOR]