Public perceptions on solar geoengineering from focus groups in 22 countries

Solar geoengineering—a set of hypothetical or unscaled proposals for offsetting global warming by reflecting incoming sunlight and lowering temperature at regional to planetary scales—maintains a vocal presence as a stop-gap measure in future climate and sustainability action¹. Recent years have been marked by indications of solar geoengineering’s rising profile and high stakes. Under such circumstances, a key dimension of assessment has been the conduct of public perceptions studies and wider forms of engagement. Public perception exercises have been largely funded by and conducted within the US, northern Europe, and Japan; yet, with prospectively planetary impacts, there is an arguable need to expand meaningful debate globally². Still, many fear that geopolitical and commercial imperatives will further complicate how solar geoengineering is advocated for and developed, and how engagement and consent from public across the global North and South will be sought^3,4.

Public perceptions of solar geoengineering have been predominantly conducted through surveys, seeking aggregate preferences of national publics on several key themes: topical familiarity, support for solar geoengineering in comparison to other forms of climate action, the conduct and location of field experiments, prospective risks and benefits, and trust in kinds of governance actors^{5,6,7,8,9,10,11,12}. A smaller body of works has explored these questions through deliberative focus group^{13,14,15,16,17} or mixed methods^18,19, seeking additionally to trace rationales and reasonings behind preferences, and to counter acquiescence bias and other framing issues that emerge in survey work. To focus group efforts can be added engagements that focus not only on general members of the public but include experts and decision-makers^20,21 or participants with expertise or organized interests²², to gauge situated or context-specific perspectives.

Our study seeks to reinforce two broad movements. Firstly, a first wave of engagements emphasizing technical questions of affordability, effectiveness, safety, and timeliness as the basis for public preferences was criticized, and partially replaced, by a second wave emphasizing open-ended deliberation of socio-political concerns, grounding in the larger context of climate action, and ‘uncoupling’ from the perceived necessity of integration into policy²³. Secondly, responding to calls to correct the endemic shortfall of global South representation in assessment^{2,24,25,26,27}, studies are increasingly expanding in that direction^{12,17,28,29,30}. Our assessment explicitly focuses on positions of the global South compared with the global North.

To ground our study, we engage with the public perceptions literature to see how a broadened set of publics nuances its most prevalent findings. Publics tend to cite lower familiarity and support for solar geoengineering in comparison to other climate action measures^18,19, citing a failure to reduce emissions or unsustainable behavior at source, geopolitical implications, and environmental impacts, as well as revealing a bias towards naturalistic framings of climate action^{7,14,17,31,32}. On the other hand, public support is impacted by perceptions of the seriousness of climate impacts^7,32,33, exposure to media coverage and prominent frames that have emerged in different contexts^30,33,34,35, and whether solar geoengineering is viewed distracting from mitigation efforts. This lattermost dimension is known in expert assessment as mitigation deterrence^36,37 although some studies contest its veracity^38,39,40, and others argue that recognizing the possibility should spur stronger climate action⁴¹.

Another key theme is on preferences for governance. There is a longstanding literature on proposed forms and functions of solar geoengineering assessment⁴² and governance⁴³, ranging from frameworks for research⁴⁴ and experimentation⁴⁵ to templates based on international treaty regimes⁴⁶, to more polycentric arrangements⁴⁷. Public perception studies show support for international coordination over upstream stages of research and field tests as well as deployment^14,31,47, or map trust for different political institutions and actors, including industry and academia^6,8,32. Comparatively few (but contemporarily relevant) studies focus on perceptions of the implications of (hypothetical) field experiments in Japan¹⁷ and the UK^16,48, which (elsewhere) have spurred social opposition and debate over appropriate governance⁴⁵. Common themes include the degree of trust in the actors conducting the experiment, and how the near versus longer-term and physical versus societal implications of the experiment are defined and deliberated.

In this paper, we explore a range of public perceptions and deliberations across the global North and global South regarding prospective benefits, risks, and corresponding governance of three major types of solar geoengineering. The first, stratospheric aerosol injection (SAI), dominates discussion—assessed as having planetary scope, comparatively low direct implementation costs, and high leverage in lowering temperatures^{49,50,51,52,53,54}. The second is marine cloud brightening (MCB), a regional approach that proposes to heighten cloud albedo^{52,55,56,57,58}. The third is space-based geoengineering, a newer entrant to the field proposing a reflective shield constructed in outer space between the Earth and the sun—supported as part of longer-term efforts to economize or populate space but questioned for its infrastructural requirements^59,60. The political implications of all three types remain deeply uncertain. Summarized in Table 1, we choose these three approaches for a balance between planetary versus regional scopes of deployment, high versus low attention in major reports, and characteristics and locales of infrastructure.

We engage with 44 focus groups (1 urban, 1 rural) in 22 countries, representing every inhabited continent (9 in Europe, 1 in North America, 3 in Latin and South America, 3 in Africa, 2 in the Middle East, and 4 in the Indo- and Asia-Pacific). To nuance our geographic and political representation, we divide these countries into three groupings: the global North (Australia, Austria, Germany, Switzerland, Poland, Spain, Italy, Norway, Sweden, the United Kingdom or UK, and the United States or US), the emerging South (South Africa, India, China, Indonesia, Chile, Brazil, Turkey, and Saudi Arabia), and the developing South (Kenya, Nigeria, and the Dominican Republic). We use the rough distinction between emerging and developing economies used by the International Monetary Fund’s World Economic Outlook reports⁶¹ to imperfectly acknowledge intra-South differences.

Our study follows a prior survey-based study³⁰ as part of a mixed-methods framework—with the survey sourcing nationally-representative preferences, and focus groups uncovering rationales and processes of reasoning that underpin preferences. Participants totaled 323, with 5–8 per group. Overt climate denialism was screened out from prospective participants, and groups were further screened for splits across gender, age cohorts, education level, income, occupation type, and region of residence (the latter four tailored by country). Informational materials (translated into national languages) were distributed to participants a week before meeting, with encouragement to discuss with one’s local community. In-meeting questioning and deliberation was based on prospective benefits and risks, as well as corresponding governance; the guiding logic was to focus conversation on actors, actions, and agendas at the most tangible scale possible. The recorded transcripts were analyzed in two parts: using qualitative data analysis software MaxQDA to code cross-country themes organized according to the questions, followed by country-by-country analyses.

Highlighting similarities and differences between the global North, emerging South, and developing South, we map how technical and societal issues raised by focus groups translate to preferences and degrees of trust for actors from different sectors (scientific, civic, industry, policy) and scales (local, national, intergovernmental), mechanisms of assessment, funding, innovation, and policy, and governance rationales. Our discussion compares focus group perspectives on the prospective development or deployment of solar geoengineering approaches to expert debates and on-the-ground developments regarding foundational assessments and experiments, research governance, and governmental or intergovernmental decision-making. In conclusion, we outline four rationales to guide further assessment, based on matching our results against our evaluation of the current governance landscape.

Rather than creating separate sub-sections for SAI, space-based geoengineering, and MCB, we report on all three together. This is because (with certain exceptions), participants discussed complexes of hope, concern, and preferred governance that are robust across solar geoengineering approaches. In Table 2, we show that focus groups referred to solar geoengineering as a broad climate action strategy or category as much as or more than individual approaches, and saw overarching, shared characteristics of solar geoengineering as meaningful. Most often, these describe the process (shading sunlight) or envisioned implications (reducing or multiplying climatic or societal harms), as well as how solar geoengineering broadly affects efforts to reducing emissions or could be affected by corporate motives, geopolitics, or civic action. In Table 3, we show differences that emerged between approaches were variations on the same theme.

We structure our results as follows. Firstly, we highlight potential synergies or trade-offs with wider climate and sustainability action. Secondly, we highlight key hopes and concerns. Finally, we move to prospective or existing governance, and the roles, processes, and rationales of overlapping sectors in assessment, industry and innovation, (inter)governmental action, and public. Our reporting navigates two needs: summarization versus allowing participants to speak in their own words. In text, we deploy summary descriptions of themes, but make use of extensive quotations in Table 4 (climate and sustainability action), Table 5 (hopes and concerns), and Table 6 (governance) to give a sense of the diversity and depth of deliberations.

Synergies or trade-offs with wider climate and sustainability action

A clear juxtaposition emerged on the relative importance and relation between tackling the symptoms versus root causes of climate change and unsustainability. Emerging global South groups exhibited comparatively stronger representation for tackling the symptoms of global warming, primarily citing the need to dampen the severity of experienced or projected impacts, and secondarily implying that there was (or should be) no clear trade-off between reducing impacts and emissions. For a smaller but North–South crosscutting plurality, solar geoengineering might buy time for more comprehensive decarbonization efforts, implying a potential synergy between tackling symptoms and causes. This perspective had key nuances in the global South context, with participants arguing that the global North holds primary responsibility for historical emissions and future reductions (Brazil, Urban), or that solar geoengineering might buy space for developing countries to further industrialize (China, Urban). The largest plurality—across North and South groups, and from most emerging South countries—posed a trade-off between symptoms and causes: that there is not only a need to address underlying systems of resource extraction and human industry and consumption, but that solar geoengineering might prolong such activities (the well-documented ‘mitigation deterrence’ concern).

Scale and leverage

Another key juxtaposition emerged on scale and leverage as criteria for preferences between planetary versus regional approaches. For some participants—represented strongly within urban groups in the South—global reach and swift climatic effects were cited as a benefit, with MCB being relatively deprioritized due to its more regional scale. For some (e.g., Kenya, Urban), this was connected to a sense of unequal deployment capacity, and that vulnerable regions might benefit from a global deployment led by technologically capable countries. Others—with comparatively stronger representation in global North groups—emphasized the double-edged nature of planetary approaches: that they would also implicate a greater range of geopolitical rationales and complications (see Geopolitics and inequity). In this sense, MCB was favored as an archetype of local-to-regional action, and envisioned as more targeted, contained, and if need be, more incrementally scalable.

Harms alleviated

Efforts to envision the key harms of climate change that would ideally be alleviated by solar geoengineering were surprisingly vague, given how precise background deliberations on experienced or projected climate impacts were. The most common response was a hope for widespread benefits: that human civilization and nature, broadly stated, could holistically benefit. This hints at some difficulty in imagining the reality of an engineered climate or the processes of sunlight reflection. At the same time, the most cited envisioned benefits were the alleviation of heat stress and improving food security. The latter was particularly well represented across the emerging and developing South as a direct concern, but with global North groups also citing food security as a systemic issue across global supply chains. Some, however, questioned the benefits and motives for large agribusinesses (Brazil, Urban), as well as whether an engineered climate would force growers to alter crops that they had adapted to a warming climate (Spain, Rural).

Side effects and infrastructure demands

An overwhelming majority of global North groups skeptically referred to solar geoengineering as science fiction—to space-based geoengineering first, SAI close behind, and MCB a distant third. By comparison, three global South groups did so. An obvious context is that science fiction is primarily a cultural medium in the global North, but it also hints at connecting deliberations in which global South groups—particularly urban groups in the emerging South—demonstrated a stronger optimism in technological innovation and capacity. Moreover, there were minority uses of this trope beyond expressing skepticism: positively, with some noting that sociotechnical systems once described as science fiction are now everyday realities, as a tool for anticipating future politics, or for comparing climate action options.

Every group deliberated on the potential side effects, uncertainties, and knowns of deploying or even considering solar geoengineering. The greatest degree of questioning emerged on unequal cooling and deeply uncertain knock-on environmental and societal effects, with many groups extending this concern beyond unintended side effects to deliberately induced unequal effects tied to geopolitical agendas (see Geopolitics and inequity). A key concern (re)emerged on food security, with concerns about unequal impacts on regional agricultural conditions offsetting previously noted hopes. Some noted that uncertainty over impacts disadvantaged vulnerable countries or populations with lower capacity to adapt to change, especially in the context of food security.

Groups across the global North and South widely questioned the energy and infrastructural costs of solar geoengineering options. Unsurprisingly, the greatest degree of skepticism was reserved for the space-based option, with participants struggling to comprehend the scale of its associated economy, and further questioning how much space debris might be created. However, participants applied comparable critique to SAI and MCB, questioning the costs and material demands for adapted aircraft or ships, the degree of innovation required, the locations for basing these vehicles (and the politics of siting), and the energy costs and emissions that would result from building and deploying such systems over extended periods. For some, this re-connected to concerns that all solar geoengineering options pose a trade-off with the fundamental logic of addressing the root causes of global warming.

Geopolitics and inequity

Most of the global North and developing South groups highlighted geopolitics: that wealthier, technology-capable states would inevitably shape deployment to their own benefits, or that incentives to do so would spur unilateral, club-based, and/or competing deployments and ensuing conflict. These concerns were shared by a strong plurality of emerging South groups – although (interestingly) no one in Indian or Chinese groups spoke to them. Other key themes emerged on the potential for a technology arms race, the underpinning context of resonant geopolitical rivalries (with combinations of China, the US, and Russia being the most cited, though not by Chinese and American participants), fears of weaponization or militarization, and potential conflicts over the location of infrastructure (e.g., bases and launch sites, or deployment zones).

Unequal capacities were acknowledged by groups from most countries, including all three developing South states, questioning if poorer countries would have the capacity to deploy any of the three approaches, or influence the planning of states that could. Groups from across North and South expressed hope that wealthier countries would seek a globally equitable set of climate outcomes in deployment. In global North groups, this was more often coupled with skepticism. Developing South groups could be more optimistic, sometimes citing economic development projects and aid.

Assessments and experiments

Groups from almost every country supported the conduct of systemic and multi-dimensional assessment, regardless of approach. Rationales covered technical and socio-political queries, as well as distributive and procedural demands: determining the distribution and impacts of shading across and within countries, calculating infrastructural costs and (extraction and location of) material resources, a whole systems perspective that emphasized impacts on different countries and societies through relief or worsening of vulnerabilities (e.g., health, agriculture, political corruption, introducing or exacerbating conflict), and constructing processes to integrate such assessments with international decision-making.

Two broad themes emerged. Input was stronger on function than form: perhaps unsurprisingly, participants deliberated with greater confidence and detail on what an ideal mode of assessment should do, rather than the processes or institutions by which it should be. Secondly, whether participants were hopeful or skeptical of solar geoengineering, envisioning the conduct and feasibility of coordinated global assessment tended to be more cautious than instrumental towards deployment. This reflected strong trust in scientists or expertise (broadly stated) – but less confidence in the capacity for intergovernmental cooperation or industry motives, to which scientific assessment was often contrasted.

Groups from a strong plurality of countries across North and South – with most countries from the emerging South – supported the conduct of small-scale field experiments, but most often with an incongruous provision: to test widespread impacts. This applied to all three approaches – but since participants understood MCB as a comparatively regional approach, they appeared to be more interested in testing the impacts of the planetary approaches. Participants tended to intuit the scaling difficulties of a space-based sunshield as infrastructure whose full impacts could not be tested at limited scales, which provided additional rationales for skepticism. However, participants tended to envision SAI field tests as contained demonstration pilots, resembling local infrastructural projects, or compared to weather modification (e.g., rain-making) schemes. Alternatively, a smaller number of groups called for testing in remote or uninhabited regions or on single countries, for an akin purpose of testing impacts while minimizing potential harms for people. This has especial implications for current controversies over small-scale field tests, which we address in discussion.

Industry

A large number of groups across the global North and South saw primary benefits for first-movers in innovation and manufacturing for all three approaches, subject to the understanding that deployment infrastructures would have to be designed and constructed. The greatest attention was paid to the space-based sunshield and to SAI, with primary benefits envisioned for the aerospace sector, and with nuances attached to a range of national aerospace industries and private companies. The US National Aeronautics and Space Administration and other national/regional agencies – the Indian Space Research Organization, or the European Space Agency – tended to be cited with greater trust. Elon Musk and SpaceX were highly cited but polarizing archetypes of a visibly emerging era of privately funded and commercialized space exploration, linking to background deliberation about the imperatives of innovation on science, technology, engineering and mathematics (STEM) in the modern global economy, and the material, intellectual and cultural resources that billionaires, major corporations, and advanced economies can marshal. Though not universally, the tone of discussion in certain emerging South groups (especially India) was characterized by greater optimism surrounding government-industry collaboration and innovative capacities – although these are complicated by concerns over unequal technological capacities in other emerging and developing South groups.

Skepticism was comparatively more prevalent (though again, not universal) in global North groups regarding excessive leeway given to advanced STEM industries, or inertial control of charismatic leaders (e.g., Elon Musk) in those industries over public discourse and policy-making. Grappling with the technical possibilities of planetary versus regional solar geoengineering, participants envisioned latent profiteering motives in patenting activities or garnering investment. An interesting dimension was noted for MCB, as an archetype of an approach with arguably more localized potential: that deployment services could be commercialized, and best benefit those able to pay. These discussions extended beyond first-mover innovators and the commercialization of deployment to benefits gained a wider range of carbon-dependant industries latching onto the prospect of solar geoengineering to continue business-as-usual – often discussed as an extension of greenwashing, and once again implicating mitigation deterrence.

Global multilateral framework

Three key rationales emerged for managing the research, development, and deployment of solar geoengineering approaches. The most widespread rationale was to ensure coordination or collaboration to forestall geopolitical contestation - groups from all global North and developing South countries spoke to this, but only half the countries from the emerging South. This rationale was underpinned by deliberations over multiple dimensions: that solar geoengineering deployment would to a large degree be a function of interstate planning; that national sovereignty and military capacity will be important factors in siting infrastructure, planning logistics, and designing deployments; that technology-capable countries (or hosting such sectors) would attempt to shape deployment to their own benefits; and that there would be complex dynamics surrounding forging alliances between states, and gaining (diplomatic, infrastructural, or military) support. A key component was the sense of deployment within a global commons, in which unilateral motivations and actions must be forestalled.

This transitions into a second – though lesser held – rationale that those affected should participate in governance, as opposed to support for technology-capable clubs – with the clearest implications emerging for the planetary-scope approaches of SAI and the space-based shield demanding global outreach and representation. Reflecting the preceding rationale over coordination, this perspective was widely held in the global North, but received much fewer mentions in the (emerging) South. The third rationale was held by a small but North–South crosscutting number of groups; aimed at technologically capable countries, it called for responsibility to help vulnerable countries. This ranged from developing solar geoengineering approaches as emergency mechanisms to alleviate or forestall climate harms, evoking disaster aid and response, to how deploying solar geoengineering could synergize with or distract from responsibility over historic emissions or forthcoming mitigation efforts.

Accordingly, there was an almost universal preference for a global multilateral organization or framework as ideal to fit these multiple functions. The envisioned functions of such a multilateral framework often extended beyond the management of geopolitics to multiple sectors and/or extended over all stages from research to deployment. Accordingly, such a body should house international expert assessments, and initiate processes for informing and consulting publics. Participants also cited the need to involve industry voices, both to encourage and coordinate technological innovation and transfer, as well as to curb profit-seeking motives.

The United Nations (UN), or the generic mention of an international body housed within the UN system, received broad citation. The most positively cited institution itself was the World Health Organization, which in the context of the Covid-19 pandemic was seen as an example of impartial science and information dissemination, and a fraught but ultimately successful navigation of political agendas in the face of global harms (e.g., vaccine politics, the origins of the virus, measures over mitigation and border control). The United Nations Framework Convention on Climate Change, by comparison, was treated more skeptically due to mixed successes and visible contestations at that institution.

A key nuance to multilateral governance was differentiation between scales. Key rationales – e.g., geopolitical management, or integrating those affected into decision-making – were commensurate to the scale of deployment between planetary (e.g., SAI and the space shield) and regional archetypes (e.g., MCB). MCB, for example, was often exempted from the need for a global level of multilateral governance, with more limited and regional arrangements – e.g., in the South Pacific or Mediterranean – deemed sufficient as long as they were representative and equitable within their zones of deployment. This reflected the juxtaposition between local-to-regional versus planetary scale and leverage, with MCB treated as being more contained in physical impacts and geopolitical implications—but it was not always assumed that agreement would be easier to reach within regional zones of deployment.

Indeed, a plurality cutting across all three country groupings highlighted the difficult of consensus or compromise within multilateral frameworks to determine an issue as complex as determining what should constitute ideal global climatic conditions. Participants most strongly cited the primacy of national sovereignty, the unclear capacities or previous failures of international law and the UN system to manage global governance issues, and harkened back to complex geopolitical and corporate agendas. On the whole, groups from the majority of global North and developing South saw multilateral governance as highly necessary – though with an unclear balance of hope in idealized global cooperation and examples of qualified success (e.g., pandemic governance), matched against resignation regarding realpolitik.

Publics

Calls for stronger consultation of publics in risk assessment were widespread, particularly across most global South countries – underpinned by rationales in favor of affected populations being included in systemic assessment and in decision-making. In turn, these contained nuances between national and global levels of consultation, and between constructive and disruptive action. Groups gravitated most towards national-to-local processes for information dissemination and public input, ranging from town halls to consultation processes or campaigns sponsored by combinations of universities, industry and government, to the election or support of political representatives. At a global level, many cited advances in the Internet and social media as platforms through which to elicit and compare preferences across national publics. Less commonly, groups cited more direct forms of (democratic) action such as (protest-based) social movements or referenda. This sense of disruptive urgency – underpinned by rationales of deep uncertainty regarding systemic risks, as well as by mistrust over government and corporate agendas – should not be lightly regarded.

These calls for public involvement and topical literacy were offset by strong skepticism over the value of public engagement – held likewise in groups across the global North and South. The most common rationale was the supposed incapacity of laypersons to grasp the technical complexity of solar geoengineering. Adjacent rationales included a lack of tolerance and/or nuance in public discourse: local or national parochialism, or a tendency towards manipulation by media trends towards polarization and sensationalism. These concerns reflected fears of the high geopolitical stakes of solar geoengineering, as well as – for groups in the global North – recent years of deep polarization regarding right-wing populism, dynamics of splintering within the European Union, social responses to pandemic management measures, and the Russo-Ukrainian War. The implications of skepticism further diverged into two camps: either offset by trust in expertise and one’s government (particularly strong within the Chinese and Saudi groups), or heightened by a sense of powerlessness and a lack of trust that governments would take public concerns into account (more common, and spread across North and South groups).

Does the Global South prefer solar geoengineering (particularly, SAI)? There is a longstanding debate among experts over the proposed benefits and risks of solar geoengineering – predominantly of SAI – for vulnerable populations, especially in the global South. Proponents emphasize that globally optimized schemes for SAI could reduce key climate risks for the most vulnerable⁶². Critics counter that SAI would likely be used by major emitters to delay decarbonization or induce geopolitical conflicts over ideal regional climatic conditions – which would disproportionately end up harming the most vulnerable³. Contentions of peremptorily speaking on behalf of Global South interests are made towards both critics³ and advocates².

Calls for public engagement in the global South²⁴ have resulted in a handful of exercises^{7,12,21,28,29,30}. Most highlight that global South participants are more supportive about the prospect of solar geoengineering¹² in comparison to those in the global North^7,29,30. Our results nuance these insights: global South focus groups exhibit greater hope but an arguably richer range of concerns for solar geoengineering, in the context of observable inequities in climate action and potential geopolitical conflict. We highlight three dimensions.

Firstly, in global South groups, there was a qualitatively stronger sense of vulnerability and immediacy that generated demand, hope, and desperation around solar geoengineering (reflecting previous work²⁸); in all groups, demand was offset by a fear of entrenching unsustainable practices. Global South groups more commonly raised the need to dampen the effects of a warming climate. For comparison, some northern European groups noted that climate impacts are (for now) less locally relevant, and that their concerns were more systemic and global. However, just as much as in global North groups, global South groups highlighted the need to reduce carbon emissions and unsustainable behavior, and warned of what experts have termed mitigation deterrence.

Secondly, the support of global South groups �� particularly from developing states – were conditioned by awareness of North–South inequities in funding, technology (transfer), commitments, and action towards decarbonization (reflecting previous work²¹). Nor was this limited to climate action, but expanded into other global governance issues—e.g., pandemic management – and geopolitical contestations. For (especially, developing) global South groups, there was a widespread demand for major powers and emitters to broadly lead on climate action, and to carry that ethic into the assessment, funding, development, technology transfer, and political coordination of solar geoengineering approaches –accompanied by considerable skepticism that they would. There was very limited discussion in developing South groups (e.g., Nigeria) on whether emerging South powers (e.g., China) could drive solar geoengineering governance in an arguably more equitable manner, acknowledging Chinese investment projects abroad as a possible reason in favor.

Finally, there was variation between the Indian, Chinese, and Saudi groups vis-à-vis Brazil, South Africa, and the rest. Discussions in the former grouping were marked by a stronger sense of national innovative capacity (e.g., aerospace) and state-industry coordination that was comparable to discussions from groups in northern Europe, Switzerland, and the US. There was also brief discussion in the Chinese and Indian groups of whether solar geoengineering might permit further space to industrialize – this discussion was not present in other groups (previous work bears the same result regarding Chinese respondents⁷). A final factor setting groups from China, India, and Saudi Arabia apart was the absence of discussion over geopolitical agendas – of their own government(s) or any other. Global North and other (more developing) South groups tended to agree on the centrality of geopolitics, with discussions reflecting the perspectives of haves and have-nots.

How do publics view early-stage field experiments? A recent companion study in our project finds that that global South publics favor further field tests in comparison to global North publics, and that no publics favor banning solar geoengineering in comparison to further assessment and testing³⁰. We engage with this finding, but first lay out the context.

Debate over the necessity and governance of early-stage, small-scale tests of solar geoengineering in the open environment – as distinct from lab-based assessments – is extremely polarized. Such tests are the first stage and scale of a longer typology of outdoor activity, ranging from initially reduced scales of testing components, deployment mechanics, and environmental processes, then moving further to time-limited impacts testing, and finally to a sustained period of deployment⁵².

There is longstanding contestation over the permissibility of small-scale tests. A lack of clear governmental guidance has contributed to an ad-hoc system of self-regulation by scientific and commercial actors, and a lack of widely accepted governance for field tests. This particularly regards the conduct of public engagement. For example, researchers disagree about whether engagement design should focus public input on localized, near-term technical and physical issues of the field trial itself, or the wide-ranging, long-term sociopolitical implications of where experiments might eventually lead⁴⁵. This has clear implications for bounding what risks are presented to publics as relevant. Critics are concerned about a ‘slippery slope’ from early-stage testing to inevitable deployment, the potential for mitigation deterrence, and deep disruptions to global governance. Proponents contend that these concerns overplay long-term anticipation ahead of what they see as ‘mundane’ basic research, and some do not see the need for public engagement at all^17,45.

In the meanwhile, considerable civic and expert opposition has followed early-stage SAI and MCB field tests. SAI tests have either been canceled in the face of civic opposition and expert dispute^45,48, or been criticized for introducing commercial motives through the sale of unilaterally defined ‘cooling credits’ or for being conducted in a clandestine manner⁶³. The most successful test was on MCB, which found a facilitative framing as (preliminarily testing) a regional form of ecosystems protection, as part of a long-term effort – an Australia-wide consortium of governmental, academic, and innovation actors – to improve the resilience of the Great Barrier Reef against climate change and other threats (the Reef Restoration and Adaptation Programme^64,65). Due in part to the infrastructural requirements, no strident calls exist for feasibility testing of (components of a) space-based sunshield that resemble debates over open-air testing for SAI and MCB⁵⁹.

Studies about public preferences regarding field tests – as opposed to deployment – are few (in Japan¹⁷, the UK^16,48, and Germany⁶), but illuminating. Participants strongly prefer that the (technical) risks should be contained and reversible, but are divided on whether the political risks could be contained – for example, the prospect of a ‘slippery slope’ from testing to deployment^16,17. Indeed, the long-term consequences of tests are treated as seriously as the immediate impacts, for both good and ill: relieving impacts on the vulnerable or future generations, or delaying mitigation and entrenching Anthropocentric hubris^6,17,48. Finally, participants are in favor of transparent governance of early-state research over moratoria or bans^16,63.

Our results confirm that global South groups favor small-scale field tests in comparison to global North groups, and add that similar rationales in favor of tests are found across global North and global South groups. However, we emphasize that public rationales delivered in the focus groups have two key contextualizing dimensions that should temper interpretations of broad support. Firstly, latter-stage climatic and geopolitical consequences are primarily of interest, rather than early-stage technical testing. Secondly, tests should be contained or remote, initially limited to smaller locales, or to particular countries – how such countries are to be identified remains an open question.

This is a mismatch between public expectation and the capacity of preferred tests, and it is particularly relevant to SAI as a more technically feasible approach with a necessarily planetary scope. In SAI assessment, small-scale, time-limited tests can examine aspects of atmospheric physics or (scaled-down) deployment mechanisms. However, gauging the differentiated physical (and political) impacts of SAI over time requires a scale and length of ‘testing’ that is equivalent to planetary deployment^52,66. Public hopes for local-to-national scales, remote locations, and contained implications^6,16,17 are impossible to meet, given the planetary scope necessitated for impacts-testing. This is similarly true of the space-based sunshield – although publics discussed the testing of this option far less, as they found imagining its infrastructure to be daunting. It is unclear if large-scale testing for MCB as a more regional approach might still meet the criteria for limited scope and containability – not least in light of the relationship with tipping points⁵⁸. The recent efforts in the Great Barrier Reef offer the insight that framing efforts around targeted regional protection could help to alleviate concern.

A caveat is necessary: participants largely did not appear aware of or discuss the distinct capacities of different stages and scales of field tests. Our study did not provide informational materials on such a typology. In the absence of such direct steering, the misconception about the capacity of contained tests to gauge transboundary risks unintentionally persisted. Nevertheless, the misconception is revealing, and prompts future work to ask: what range and scales of field tests would be deemed permissible, if publics understood that no such tests below global deployment would answer their most salient concerns? How would public expectations over the knowability of future outcomes be adjusted? Would public support in the global South or North be altered for SAI or solar geoengineering more broadly?

Our results do not imply that publics would oppose early-stage, small scale field tests with limited technical objectives. It is worth noting that many participants – more in the global North than South – stated that they would oppose any indication of solar geoengineering development, implying the inclusion of field tests. However, our results show that participants across the global North and South would conditionally support tests – though far more in the South than North – as part of systemic risk assessment that combines technical and socio-political inquiry, demonstrates international collaboration, and eschews commercial motives (reflecting previous work¹⁶). Engagements over field tests in particular locales also offer opportunities to extrapolate and explore how ‘whole systems’ of development and deployment⁶⁷ might be distributed: each solar geoengineering approach, and variations of deployment schemes within each approach, would have resource demands and locations for infrastructure that would directly affect certain actors over others⁶⁸.

Moreover, the misconception over the capacity of contained field tests was not universal, with a smaller number of inputs acknowledging the impossibility of field-testing for long-term differentiated impacts, and in its place, noting the need for extensive simulations (reflecting previous work^16,17). Certainly, this validates an expanding range of earth systems modeling studies⁵⁴ that is beginning to inquire after impacts relevant to global South countries and regions^69,70,71. At the same time, a prominent strand of modeling works on constructing idealized deployment schemes to construct globally optimal climatic outcomes⁵¹. While providing a basis for international coordination, optimized scenarios are at odds with conflicting, geopolitically-motivated agendas and non-ideal deployments – which are not only a strong focus of our focus group deliberations, but remain greatly underassessed in both modeling and broader assessments^44,72,73. It will be necessary to bridge climate modeling with expert, policy, and public engagement to construct a range of geopolitically cooperative and conflicting scenarios^74,75,76.

Multilateral, multi-purpose, and multi-stage governance is seen as ideal. Our results show support for the pursuit of multilateral agreements between states – most often citing a UN-based framework as template – from groups in the global North and developing South, as well as in groups from half the emerging South countries (including China and Brazil). Moreover, publics were concerned not only with managing the geopolitics of deployment, but discussed the need to coordinate assessment, development, and – especially for global North groups – screening out commercial motives. These results broadly confirm previous studies that show support for international coordination over upstream stages of research and field tests as well as deployment^14,31,77, and show that support is conditioned by trust in political institutions and actors, including industry and academia^6,8,32.

Three adjoining insights are notable. Firstly, the scope of inclusion in decision-making was almost always fitted to the geographic/geopolitical scope of the approach’s impacts, but with differentiated rationales. For global North groups, the key guiding principle was explicitly based on all affected populations and countries being represented in decision-making, rather than just technology-capable countries. In contrast, groups from all three African countries and the Dominican Republic voiced a hope that decision-making would include countries lacking technological capacity and with greater climate vulnerabilities. Emerging South deliberations almost completely lacked either rationale – this fits with the comparatively lower support for formal multilateralism expressed therein, and speaks to the logics of an emerging multi-polar international system.

Secondly, unilateralism, coalitions of the willing, and competing deployments^78,79,80 were spoken to as plausible across global North and South groups, but we warn against extrapolating interpretations of support for them. Concerns about multilateral frameworks were most often based on skepticism that they could work. However, this never translated into open consensus in any group for unilateralism or coalitions of tech-capable major powers – even in countries where multilateral governance was not clearly supported. Some developing South groups questioned if they might benefit from being sponsored by more powerful actors in ad hoc or mini-lateral arrangements, but were more often concerned about a lack of geopolitical leverage. Meanwhile, groups in the North or the emerging South treated such arrangements with a combination of caution and ambivalence: if deployments might not be collectively optimal, would they be singularly (dis)advantageous? Much depended on how participants trusted the capacities of their national governments.

Thirdly, no groups discussed moratoria or bans for any kind of solar geoengineering as a governance option – either in support, or against. We again note results that moratoria and bans have seen less public support in comparison to further assessment and even development – although support for moratoria and bans constitute strong minorities globally, and tend to be higher in the global North^16,30,63. Unfortunately, our results could not provide clarity on such preferences. A key reason was likely the design of the focus groups: participants were explicitly asked to consider what actions needed to be taken “before there is consideration to implement this approach” (see Methods), which created less discursive room for prohibitive frameworks. We might also consider how high levels of skepticism toward SAI and the space-based sunshield, especially in the global North, might have translated in deliberations that compared permissive and prohibitive frameworks. Nevertheless, there is a clear gap between public and expert understandings of the value of (temporary) bans, which have received a degree of support from both proponents of further research and testing (applying only to deployment⁸¹) as well as critics (applying to government funding, testing, and deployment³).

In sum: for the majority of groups, a prevailing need for nose-to-tail collaboration across stages and scales of activity was strongly offset by geopolitical issues and skepticism over the capacity for such collaboration. Some of this is mirrored by how expert conversations have evolved in the last two decades from legal, international regulation of deployment⁷⁸, towards combinations of international institutions as templates for a range of permissive or prohibitive functions⁴⁶, and finally towards more pragmatic, polycentric arrangements of research governance^43,47. This has been due to two factors: a lack of clear fit with the mandate of any single existing multilateral governance institution (a situation that persists), and because there was until recently little appetite at various global bodies to consider solar geoengineering governance. For example, efforts to introduce such discussions in 2018 at the UN Environment Programme (UNEP) failed⁴⁷. In the near term, the most relevant governance mechanisms remain those of the Convention on Biological Diversity^82,83 and London Convention and Protocol on marine pollution (specifically, on geoengineering approaches in marine environments^84,85), which maintain rules on the scope of legitimate research.

The situation may be shifting. The European Commission, the UN Educational, Scientific and Cultural Organization (UNESCO), UNEP, and the UN Human Rights Council have drafted anticipatory principles or reports to ground future engagement – which remain preliminary and precautionary in nature^86,87,88,89. Nevertheless, it reopens a discussion about whether a piecemeal, sum-of-parts coordination between institutions could plausibly be found⁴³, or whether the challenges of planetary forms of solar geoengineering would distort existing regime mandates and agendas³. Moreover, distinctions between approaches imply different architectures. Regimes such as the Outer Space Treaty of 1967, which establishes outer space as the “province of all mankind”, and the UN Commission on Peaceful Uses of Outer Space, which promotes that benefits of space technologies be extended to all, might be applicable to space-based geoengineering⁵⁹. MCB may eventually qualify as a form of marine geoengineering (currently, only ocean fertilization does); the London Convention and Protocol has the clearest regulations of any institution on the scope of field testing. SAI – arguably the most visible of all options – has no clear landing spot, and key advocates underplay the need for one⁴³. It remains unclear from our results whether global publics would see a polycentric variant of international governance as desirable or pragmatic, compared to arrangements with clearer mandates and oversight.

Finally, publics often expressed powerlessness regarding any meaningful role in consultation or decision-making. The degree of scepticism over the value of public consultation across global North and global South groups regarding the two planetary approaches – SAI and the space-based sunshield – was surprising. Our results show a widespread recognition that individuals and communities would likely play no direct role in decision-making – complexes of powerful governments and (private) industries would inevitably shape innovation and deployment. This echoes an old debate in SAI governance: whether a planetary technology necessitates a more aspirational, direct, and deliberative shape of democratic control¹⁴, or whether democratic input can assume a less ideal, more conventional shape, filtered through political representatives and an evolving range of norms and institutions⁹⁰.

Our results show that under conditions of deep uncertainty, global North groups (with implicit trust in their nations’ geopolitical and innovative capacity rather than the sitting government) and some emerging South groups (with explicit trust in their political system) seem either resigned to or comfortable with the latter shape of democratic input. In addition, confidence in technocracy – for example, positive references to Elon Musk – played a minor but strident role. However, we should also note countervailing mistrust regarding both government and industry.

Indeed, there are further reasons for concern that should provide impetus for designing new, more ambitious forms of public input. Groups cited a variety of additional rationales reflecting doubt in the value of public consultation: technical complexity, national or local parochialism, media sensationalism, and the high geopolitical stakes involved. Each rationale is a concerning dimension of public discourse. Taken together, they betray a lack of confidence in public discourse itself. Falling trust in public discourse – or at least, greater ambiguity – is particularly discernible in global North groups, who cite recent political events in which public (mis)information played crucial roles.

Given this troubling implication, future research might consider innovating processes for public consultation^2,24 that avoids leaning into the functional entrenchment of solar geoengineering into policy⁹¹ through framings of climate emergency⁹². There may be benefits to generating a global public discourse at this foundational stage: recall the rationales that all affected should be consulted (more prevalent in global North groups) and that the powerful should incorporate the needs of the powerless (more prevalent in developing South groups), as well as concerns about powerlessness cutting across all groups. At the same time, the logistics are daunting – particularly for the planetary approaches. Our study offers a template for a global scope of study, although it is limited by the time and funding available to academic grants (as well as the limited topical familiarity of publics). Again, there are few calls for such engagements to take place regarding a space-based sunshield. But for SAI, non-government organizations are conducting and planning engagements in the global South^93,94. Conversations amongst research advocates in the US have turned to national programs of assessment^4,52,95, which must include sustained public engagement initiatives^4,96. There will be a future need to aggregate polycentric engagements, should these escalate. Our study may prove useful as an early global baseline, identifying key hopes and concerns as well as crucial areas of dissonance within and between countries.

In closing, we highlight four rationales to guide further assessment, based on the results of our global focus group deliberations, and on our judgment of shortcomings in the research and governance landscape (Fig. 1).

To the left are the three types of solar geoengineering. The pictures are those provided in information materials sent to participants. The solar geoengineering types are connected to hopes (in green), concerns (in orange), and themes with elements of both (in yellow). Governance rationales and activities are in blue. The arrows signify linkages between hopes, concerns, and corresponding governance; the colors of the arrows correspond to the aforementioned scheme – positively, as a hope (green); negatively, as a concern (orange), both (yellow), and connections between governance (blue). The darker the color of the boxes, the more focus groups spoke to the theme contained therein. These complexes connect to one or more of the four governance rationales in the conclusion, outlined in the black blocks to the right. The smaller colored circles refer to relative emphases placed on themes by focus groups from the global North, emerging South, and/or the developing South.

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Firstly: assessment should question SAI’s inertial dominance over other solar geoengineering approaches in expert assessment and nascent policy conversations. Comparatively low implementation costs and swift, global leverage on reducing temperatures have become received wisdoms, and are argued to justify the focus on SAI⁵². Fundamental technical uncertainties continue to confront MCB⁵⁷, and assessment of a space-based shield remains nascent⁵⁹. However, our results show that much public hope and concern center around a planetary versus regional dichotomy. A planetary reach implies greater climatic leverage, but more complex side effects and politics, and demands more comprehensive, inclusive input into decision-making – and vice versa. Public support exists for more regionally bounded approaches, and this is worth noting in light of non-SAI proposals for protecting keystone systems – such as the Great Barrier Reef⁶⁵ or Arctic and Antarctic sea ice⁹⁷.

Secondly: polycentric governance may not be sufficient. Our results show that participants (though somewhat less in certain emerging South powers) prefer international collaboration from upstream stages of research onward. This preference is offset by scepticism regarding the feasibility of effective multilateralism, and by degrees of confidence regarding national capacities to pursue geopolitical interests – but these, by themselves, are never preferred to multilateralism. Polycentric research governance – diverse and distributed scientific networks, national programs, and bodies of norms and rules for field tests – may be a pragmatic avenue today⁴⁷. But path-dependence is a concern. In time, polycentricity at upstream stages might become formalized in field-testing and even deployment, entrenching conflicting and multipolar logics. A US-based assessment program should be aware of the optics and incentives generated in unilateral action⁹¹. The danger of jurisdiction shopping between international institutions and regimes remains underassessed⁹⁸.

Thirdly: assessment must become re-geared towards political questions. In recent years, solar geoengineering assessment – again, dominated by SAI – has primarily consisted of earth systems modeling studies, and contestations over the permissibility of small-scale field-tests. Our results show that publics are hopeful about the prospect of solar geoengineering to alleviate a range of climatic harms, but this is heavily offset by the reality of geopolitical inequities, and the plausibility of contestation and conflict. Modeling globally optimal deployment schemes and climatic benefits treats geopolitical conflicts as if they do not exist, and form an incomplete basis for informing decision-making^44,72,74. All areas of assessment can be better geared towards political questioning. There is a need for more direct engagement with national strategic and security planning communities, instead of taking a benevolent global planner perspective^21,73. Climate modeling can be combined with expert, policy and public engagement to construct a range of scenarios that reflect not only optimal schemes, but conflicting schemes that serve the priorities of different (groupings of) states⁷⁴. Assessment – with field tests providing an additional opportunity – can examine commercial interests (e.g., patenting, cooling credits), or anticipate whole systems of infrastructure, resources, and zones of deployment⁶⁷. We have seen indications of falling trust in public discourse that should be combatted; global public discourse on solar geoengineering might be enhanced through innovative, transnational forms of input.

Finally, assessment should refine and disaggregate the interests of the global South. Our results show intra-South differences in perspective between participants in emerging powers (especially China, Saudi Arabia, and India) and other global South countries, particularly less developed states. Differences center around technological capacity and geopolitical clout, where global North and emerging global South powers have more comparable capabilities. Developing South participants conceived of their interests being – at best – protected or sponsored within bilateral, minilateral, or multilateral arrangements driven by more powerful states. Given the prospects of an emerging multi-polar world with a shifting, a la carte approach to international alliances, assessment will need to take a more fluid approach assessing solar geoengineering politics than exclusive reliance on global planner or North versus South lenses would permit.

Inclusion and ethics statement

All components of the research were granted ethical approval by the Research Ethics Committee of Aarhus University (#2021-13). Full and informed consent was given by all participants before the beginning of the study, along with all participants being notified about the fact that their data would be handled in a fully anonymous manner and in complete accordance with the General Data Protection Regulation and any other pertinent data-security regulations, that any data would be analyzed in an aggregate fashion and would not be personally identifiable in any way, and that they had the right to withdraw their participation at any time. The research has been broadly undertaken with the aim of better understanding public perceptions of solar geoengineering approaches, including in the Global South and by means of more qualitative methods that can better elucidate the variability and importance of the local context. At this stage, no local researchers have been included. The specific roles and responsibilities of those in the author team was discussed prior to the research. Insofar as possible, we have striven to have taken into account local and regional research in the citations.

Mixed methods framework

We utilize a multi-methods framework combining (a) a survey instrument with (b) focus groups. The two methods are complementary. The large-N survey³⁰, given statistically significant sample sizes and screening, sources aggregate and nationally representative preferences – but gives less sense of rationales and processes of reasoning that underpin preferences. Focus groups aim to map such rationales, with the in-depth treatment and detail that comes with deliberation, and with references to local or national contexts that can inform further situated (or locale and context-specific) assessment. The survey’s design and results³⁰ examines both carbon removal and solar geoengineering approaches. The focus groups form the basis of two papers: this paper, and another on carbon removal⁹⁹.

Carbon removal

The run-time of each focus group was evenly split between discussion of solar geoengineering and carbon removal approaches. These two suites of approaches have historically been grouped together under the umbrella concept of (climate) geoengineering, or increasingly, climate interventions. Debate on whether solar geoengineering and carbon removal should be separately (representing different socio-technical characteristics and governance demands) or comparatively assessed (for synergies and trade-offs in the context of wider climate action) remains inconclusive. This paper focuses on solar geoengineering, while a twinned paper on carbon removal has been recently published⁹⁹.

Urban versus rural

Due to a need to refine the focus of this paper, we chose not to undertake a deep investigation of the differences between perspectives of urban versus rural groups cutting across approaches and countries. A separate paper that examines these dimensions is in preparation.

Country selection

We conducted 44 focus groups (1 urban, 1 rural) in 22 countries: the United States of America, the United Kingdom, Australia, Germany, Austria, Switzerland, Italy, Poland, Norway, Sweden, Spain, South Africa, India, Chile, Brazil, China, Turkey, Saudi Arabia, Indonesia, Kenya, Nigeria, and the Dominican Republic. We aimed at a split between countries in the global North and global South, geographic spread across UN/continental regions, and inclusion of regional powers. A prior stage deployed a survey instrument in 30 countries was deployed in a prior stage. These included all 22 countries assessed in this study, as well as Canada, France, the Netherlands, Norway, Estonia, Greece, Denmark, Singapore, and Japan³⁰. Constrained resources led the reduction of countries from the survey to the focus groups; the countries removed are all in the global North, in keeping with our desire to expand the geographic scope of assessment to the global South.

Participation and recruitment

In total, 323 participants were part of the focus groups. Recruitment aimed at 8 participants per focus group, and achieved at least 5 per group despite technical difficulties and dropouts. Norstat, a European-based data collection company (https://norstatgroup.com/), conducted the recruitment of participants in collaboration with the authors.

Prospective participants were screened via an online survey for several mandatory criteria. These criteria were defined in collaboration between the authors and Norstat. Prospective participants displaying an overt degree of climate denialism were screened out – defined by answering “No” to “Do you believe climate change is happening?”. Focus groups were further screened for an even split between female and male genders, and between 18 and 44 year-old and above 45 year-old cohorts. For division into urban (including suburban) and rural focus groups, participants were screened through self-definition, by responding “Urban”, “Suburban”, or “Rural” to the question: “How would you describe the area in which you live?”.

Two further soft screens (guiding but not mandatory) were held. The first was for distribution across education level, income, and occupation type, each tailored by country. The second was for distribution across within-country regions within, in most cases defined by formal (e.g., federal) administrative regions. A smaller number of countries (USA, India, Brazil, Indonesia) with a high number of administrative regions were defined by broad geographic regions.

Materials and languages

Two sets of materials were developed by the authors in collaboration with Norstat. The first was a discussion guide of questions and instructions for moderators. The second was a set of information materials on solar geoengineering (and carbon removal) approaches that were distributed to participants beforehand. Materials were written originally in English and communicated in that language with focus groups in US, UK, Kenya, Nigeria, South Africa, Australia, and India. Materials were also translated by Norstat personnel into: German (Germany, Austria, Switzerland); Italian (Italy); Polish (Poland); Norwegian (Norway); Swedish (Sweden); Spanish (Spain, Chile, Dominican Republic); Portuguese (Brazil); Mandarin Chinese (China); Turkish (Turkey); Arabic (Saudi Arabia), and Bahasa Indonesia (Indonesia). To ensure quality, academic colleagues in climate and energy governance known to the authors translated key technical terms from English into their native languages, for use by Norstat translators.

Discussion guide

The discussion guide consisted of the following groupings of questions. The guiding logic was to focus conversation on actors, actions, and agendas at the most tangible scale possible.

The first grouping of questions was based on prospective benefits: What are the benefits from any of these approaches? Who might gain the most from these benefits, and why? If these were implemented in your community or country, who would be affected positively – and how and why?

The second grouping of questions was based on prospective risks: What are the risks from any of these approaches? Who might be most negatively impacted from these risks, and why? If these were implemented in your community or country, who would be affected negatively – and how and why?

The third grouping of questions was based on governance responding to prospective benefits and risks: In an ideal world who are the most important people that should help make decisions on this approach – in your community, or your country, or even the world? What actions should be taken before there is consideration to implement this approach – what would you like to see done? How would you want yourself, and the wider public, to be involved in making decisions on these approaches?

A concluding ‘headlines exercise’ as a creative mini-scenario exercise was held: Participants were asked to create a (newspaper) headline in 2030, with four elements: an approach, an actor, and an event, in sum representing a good or bad outcome related to the approach (a headline that makes the participant feel hopeful or worried).

Informational materials on approaches

Information materials were sent to participants a week prior to the conduct of the focus group. Participants were encouraged to do further research, and to discuss with members of their community¹⁰⁰. This step was taken to account for the limited discussion time, the lack of feedback and deliberation with technical experts, and a lack of directly lived experience with regard to these approaches.

The information materials consisted of the following elements. There was one introductory page each for carbon removal and solar geoengineering separately, with short points on overarching technical characteristics. Each approach was then accompanied by a column of approach-specific text, taking up one-third to half a page each. Each column contained: a brief technical description; a picture deliberately stylized to avoid reification; a short list of infrastructural needs; and one to two technical pros and cons that were abbreviated to forestall as much framing as possible.

Meeting logistics

The majority of meetings were conducted online, via Zoom (version 5.17.7 (31859)), which we selected for ease of logistics, costs, recording, and transcription. Meetings in Dominican Republic, Nigeria, Kenya, South Africa, and the rural group for India were held in person or in hybrid format. Meetings were moderated by Norstat personnel, in the same language as the translated materials. All focus groups ran from 2 to 2.5 h. The carbon removal and solar geoengineering suites each received half the allotted time. Half of the focus groups began by discussing carbon removal, and the other half with solar geoengineering – the division was made at random by Norstat. We recognize that the time allotted was limited in comparison to other deliberative exercises, which we defend as necessary given our financial resources and the inclination of our research design towards greater geographic coverage, particularly in the global South.

Transcription

Online groups were recorded via Zoom. Various other recording mediums were used for hybrid and in-person groups. Norstat transcribed all deliberations. Transcribers and the authors undertook multiple rounds of clarification to ensure accuracy and quality.

Coding and analysis

The authors conducted a two-part analysis. The first part used qualitative data analysis software MaxQDA (Standard 2022, Release 22.8.0, (c) 1995–2022 VERBI GmbH Berlin) to code themes across focus groups and countries. The coders were Sean Low (SL) and Livia Fritz (LF). SL coded all urban groups and LF coded all rural groups, alongside frequent inter-coder reliability checks. Coding followed the questions of the discussion guide, cross-referencing solar geoengineering approaches with perspectives on: (a) Climate change causes and impacts; (b) Benefits and ‘Winners’; (c) Risks and ‘Losers’; (d) Governance; and Publics, with further coding emerging on (f) Contexts and analogies and (g) Technical uncertainties. The second part consisted of writing qualitative summaries on each focus group; then combining the urban and rural portions into country-by-country analyses. LF analyzed all rural groups; SL analyzed all urban groups. The key technical and societal issues presented in the results section are derived primarily from the thematic coding, supplemented by the country-by-country analyses when differences between countries or groupings of countries required further clarification.

Reporting summary

Further information on research design is available in the Nature Portfolio Reporting Summary linked to this article.