ABSTRACT Marine climate interventions (mCIs) are ocean-based approaches to support climate change mitigation and/or adaptation. Carbon dioxide removal approaches focus on reducing atmospheric greenhouse gas concentrations through enhancing ocean carbon uptake and storage. Solar radiation management proposals aim to shade and cool vulnerable marine ecosystems. How research is progressed into these two types of mCIs over the coming decade will be critical to enable responsible research and deployment, ensuring that Australian scientists and policymakers can make informed decisions. We consider the technical, social, and governance challenges that must be overcome in the next decade and identify three strategic priorities: (1) intensify research into current and future mCIs; (2) enhance Australia’s monitoring, reporting, and verification capabilities; (3) enact targeted governance and engagement strategies, ensuring the inclusion of affected communities and First Nations in research decisions. These are prerequisites to determine whether, how, and at what scale mCIs may be deployed as part of Australian climate policy.

Stratospheric aerosol injection (SAI) using diamond dust has been proposed as a solar radiation management (SRM) technique to mitigate global warming by scattering incoming solar radiation, offering advantages over sulfur-based aerosols such as reduced ozone depletion and acid rain risks. However, detonation synthesis—the most economical method for large-scale nanodiamond production—inevitably introduces sp 2 -hybridized carbonaceous impurities, often forming shells around diamond cores, which may enhance shortwave absorption and undermine SRM efficacy. This study employs density functional theory and ab-initio molecular dynamics to model these impurities across hydrogen-to-carbon (H/C) ratios from 0.0 to 1.0, revealing a continuum of optical properties in which decreasing sp 2 content reduces the imaginary refractive index ( k ). Particle-scale core-shell Mie scattering simulations at 550 nm for diamond cores of 300 nm diameter with carbonaceous impurity shells (1.95 + k i refractive index, shell thickness of ∼0.1–10 nm corresponding to 0.1–10% impurity mass fraction) show that these impurities elevate the effective mass absorption coefficient to up to ∼1 m 2 /g—nearly 15% that of black carbon (∼7.5 m 2 /g)—and decrease single-scattering albedo by up to 25% relative to pure diamond. These absorption enhancements, driven by the impurity shell’s k and mass fraction, could shift diamond dust's radiative forcing toward warming. Our findings highlight the critical need to revisit diamond’s efficacy as an SAI candidate material. • Strongly scattering diamond dust is proposed for Solar Radiation Management. • Economical detonation synthesis introduces > 5% sp 2 hybridized carbon impurities. • Density Functional Theory revealed a range of highly light-absorbing impurities. • Trace impurities on diamond particles introduce shortwave absorption. • Impurities decrease diamond’s scattering by up to 25%, questioning its efficacy.

This study investigates how Solar Radiation Management (SRM), particularly through Stratospheric Aerosol Injection (SAI), influences evaporative heat flux—also referred to as latent heat flux (LE)—across West Africa. The region is highly sensitive to climate change due to its dependence on rain-fed agriculture, limited water resources, and frequent heat stress events. Understanding how geoengineering could affect surface energy and moisture exchange is therefore essential for future climate planning. We use a combination of datasets and climate modeling frameworks, including ERA5 reanalysis, CMIP6 simulations under two Shared Socioeconomic Pathways (SSP245 and SSP585), and results from the ARISE-SAI geoengineering experiments. The analysis covers four time periods: pre-industrial baseline, present conditions, near-future projections, and far-future projections. Across all datasets, a distinct latitudinal gradient in LE emerges: higher latent heat flux values occur in coastal, vegetation-rich areas, while significantly lower values characterize the drier Sahel. This pattern highlights the central role of surface moisture availability and land cover in determining evaporative heat flux. Under the high-emission SSP585 scenario, regional warming alters energy partitioning at the land surface, intensifying evaporative stress and increasing the likelihood of drought and agricultural losses. In contrast, SAI reduces warming, decreases extreme evaporative losses, and shifts LE values closer to those of the pre-industrial period. Cooling effects are strongest in humid coastal zones, where enhanced moisture availability supports a more pronounced response. Overall, the study suggests that SRM—if carefully managed and supported by emission reductions—could help reduce climate-related water and food insecurity in West Africa by stabilizing evaporative processes and moderating extreme heat conditions.

Scalable all-in-one electrochromic glazing for full-spectrum solar radiation management

We assess the impact of two solar radiation management (SRM) approaches, stratospheric aerosol injection (G6Sulfur) and solar radiation dimming (G6Solar), on SSP5-8.5-projected changes in summer monsoon precipitation across Afro-Asia for the mid-future (2040-2069) and far-future (2070-2099) periods, using Geoengineering Model Intercomparison Project (GeoMIP) experiments under CMIP6. Relative to SSP5-8.5, both SRM methods increase consecutive wet days (CWD), largely due to an enhanced increase in light-to-moderate precipitation rates (0.1-10mm/day). Heavy precipitation (>10mm/day) decreases across all three monsoon regions, leading to widespread reductions in mean precipitation, precipitation variability, and very heavy precipitation extremes (RX5day, R95pTOT), with far-future decreases nearly twice as large as those in the mid-future. Moisture budget diagnostics show that SRM-induced reductions in mean precipitation are driven primarily by a weakened vertical thermodynamic term, linked to reduced specific humidity resulting from SRM-induced cooling. Furthermore, SRM modifies projected precipitation seasonality. In the mid-future, precipitation onset is delayed by ∼3days over most regions, while heterogeneous shifts in cessation result in little net change in season length. By contrast, in the far-future, earlier onset and later cessation lead to an extension of the precipitation season by up to ∼5days. Urban and rural population exposure to wet and dry extremes decreases substantially under both SRM methods, except over South Asia and West Africa, where exposure to CWD increases. Overall, both G6Solar and G6Sulfur show potential to reduce the SSP5-8.5-induced intensification of Afro-Asian monsoon precipitation, while producing notable spatial and temporal heterogeneity in the monsoon response.

Roadmap toward a Planetary Sunshade for Space-based Solar Geoengineering

ABSTRACT Negative effects of anthropogenic climate change are accelerating. The threat climate change poses has prompted research into radical technological responses, including forms of solar radiation management (SRM). While there has been some consideration of the ethical challenges SRM technologies present, to date, these have almost exclusively concerned humans. Here, we take one leading form of SRM, stratospheric aerosol injection (SAI), and examine the ethical questions its deployment might present for wild animals. We map this terrain by investigating two overarching ethical questions: a) whether deploying stratospheric aerosol injection should be seen as in-principle wrong from animal ethics perspectives, and b) if not, or where it is not, what ethicists need to consider to morally evaluate SAI in the context of wild animals. To address the second question, we explore existing research gaps regarding empirical information on the effects of SAI on animals, the possible impacts of SAI on animal welfare, and its potential implications for justice issues when animals are included in theories of justice.

Why do actors oppose the development and potential future use of solar geoengineering technologies? This article maps and analyzes growing opposition to the development of planetary-scale solar geoengineering technologies among three actor groups—governments, civil society and academics. While much social science research on such technologies has addressed questions of feasibility, acceptance, legality, the desirability of more research or hypothetical governance designs, hardly any empirical analyses exist of the opposition to these technologies. Drawing on numerous policy documents, civil society declarations and academic statements, this article identifies eight diverse rationales that underpin current opposition from governments, intergovernmental bodies, civil society and academic communities to solar geoenegineering. These rationales include concerns about risks and uncertainties of potential solar geoengineering schemes, their failure to address the root causes of climate change, risks of delaying mitigation, likely violations of international law, entrenchment of unjust power relations, presumed ungovernability, technological hubris, and the violation of the Earth’s integrity. Our analysis also finds evidence of cross-fertilization among these rationales and a gradual normalization of a global ‘non-use’ discourse. Overall, these critical perspectives increasingly shape the normative and political terrain within which solar geoengineering is being deliberated.

ABSTRACT Those who have asked who should compensate for harm due to solar geoengineering have been preoccupied with a version of the Polluter Pays Principle according to which compensatory obligations befall deployers of the technology. But there is an alternative (but not mutually exclusive) interpretation. According to it, non-deploying greenhouse gas emitters are liable to compensate for harm due to solar geoengineering since they have contributed to the circumstances rendering it an understandable response to the threat of climate change. Such an Emitter Pays Principle is normatively attractive, especially in cases where deployment is a venial act of self-defense.

Global warming (GW) contributions from feedbacks and feedback loops are projected to rise from ≈54% (loops: 29%) in 2024 to ≈71% (loops: 50%) under faltering RCP pathways without Solar Geoengineering (SG) by about 2100. A critical threshold, RCP_Critical, defined as the point at which feedback loops account for more than half of GW, is projected to occur between 2075 and 2125. Beyond this point, reversing warming becomes severely constrained, and climate tipping points become more likely. From these trends, an average mitigation difficulty and cost increase rate (MDCR) of ≈1.33–1.5% per year is estimated. By 2100, absent mitigation, the effort required to offset global warming would roughly double relative to today, approaching an unsustainable mitigation critical threshold. Current feedback levels may already be driving nonlinear warming behavior. These diagnostic estimates align with three key indicators: a minimum-feedback baseline from 1870, an equilibrium climate sensitivity (ECS) range of 3.1 °C–4.3 °C (potentially reached by ≈2082), and consistency with IPCC AR6 confidence bounds. In response, this study proposes Annual Solar Geoengineering-PLUS pathways (ASG+Ps) as supplemental measures. These include Earth Brightening, targeted Arctic Stratospheric Aerosol Injection (SAI), and feasible L1 Space Sunshade systems designed to reduce feedback amplification and extend mitigation timelines. The “PLUS” component refers to the use of increased mitigation levels with a focus on high-amplification regions, particularly the Arctic and the tropics, to help reverse local feedbacks and promote negative feedback loops. These moderate ASG+P pathways directly address AR6 concerns while avoiding many governance challenges of full-scale SG. ASG+Ps are less controversial and provide ≈14× stronger cooling potential per Wm−2 than Carbon Dioxide Removal (CDR), while allowing variable regional targeting. Meanwhile, RCP2.6 has already been missed, placing RCP4.5 and RCP6 at risk. In 2024, atmospheric CO2 rose by ≈23 Gt (≈3 ppm), while forest tree losses exceeded afforestation gains by 2×, yielding a 2 GtCO2 sink loss, further diminishing CDR’s effectiveness. Declines in planetary albedo since 1998 continue to amplify warming. Urbanization accounts for roughly 13% of total surface GW, affecting 60% of the population, underscoring the mitigation potential of urban Earth Brightening. New results here also show major Space Sunshading area reductions, at ≈32× less than prior flawed estimates (detailed here) and ≈1600× less under the ASG+P method, substantially improving feasibility and the importance of space agencies’ needed mitigation role. A coordinated global ASG+P strategy, supported by IPCC working groups and space agencies like NASA/SpaceX, are needed to provide a critical supplemental pathway for climate stabilization. Given the shrinking intervention window, rising MDCR, and the escalating risks to civilization, prioritizing timely work in this area is essential; the investment is minor compared to the trillions in climate financial damages that could be avoided.

Solar geoengineering interventions are designed to reflect sunlight and reduce the impacts of climate change. These are attracting increased 62Defence Strategic Communications | Volume 16 | Autumn 2025DOI 10.30966/2018.RIGA.16.3research and policy attention while simultaneously being targets for disinformation campaigns and conspiracy theories. The technical complexity, scientific uncertainties, and governance controversies of climate cooling technologies create ideal conditions for information manipulation, making them vulnerable to exploitation by malign actors. Influence operators have already demonstrated sophisticated capabilities in exploiting weather modification and climate change narratives for strategic advantage. This establishes a precedent that could see solar geoengineering disinformation used as a hybrid threat and an inevitable focus of future influence campaigns. This article analyses the implications of solar geoengineering disinformation, demonstrates how malign actors could exploit scientific and governance uncertainty for geopolitical advantage, and introduces a strategic communications framework to guide policymakers, researchers, and communications professionals on mechanisms to preserve space for rational deliberation on these technologies. The goal of the framework is not to promote or discourage solar geoengineering research or deployment but to protect the conditions necessary for informed democratic debate. The disinformation threat considered here does not arise from adversary opposition to (or support for) solar radiation modification per se, but rather from campaigns designed to prevent conditions necessary for evidence-informed debate and democratic choice. The capacity for evidence-based deliberation about climate cooling represents a crucial test of democratic resilience in contested information environments.

The Tollgate Principles (‘TGPs’) aim to represent ‘the price that must be paid’ by anyone claiming to be ethically serious about pursuing solar geoengineering (Gardiner and Fragnière, Ethic Policy Environ 221(2):143–174, 2018). The TGPs are influential but, like other governance principles, have also provoked criticism. This paper clarifies the Tollgate approach by responding to objections and dissolving some perceived tensions. It argues that, while not the final word, the TGPs are an important step in the evolution of geoengineering governance and should continue to be taken seriously at all levels. It concludes that rather than “beware the Toll Keepers” (Briggle, Ethic Policy Environ 21(2):187–189, 2018) we should instead “beware the Toll Dodgers”: those who would brush aside the TGPs and other ethics-centered approaches. As well as defending the Tollgate approach specifically, the discussion provides broader lessons for governing geoengineering and other controversial technological interventions.

How does existentially dangerous technology get adopted and then locked in? The case of the atomic bomb offers a cautionary tale. In the long run, reliance on nuclear weapons is a recipe for catastrophe. Yet their perceived ability to reduce the frequency of war in the short term inhibits efforts to reform the international status quo. Drawing on the pioneering work of David Collingridge and Nathan Sears, this paper argues that nuclear deterrence became locked in for several reasons: initial disagreement about the threat it posed, the threat’s declining salience as time wore on and serial procrastination in addressing it. Unfortunately, the same is likely with any technology that involves low-frequency, high-impact risks, including solar geoengineering and possibly artificial intelligence. At worst, it can convert catastrophic risks to existential ones, while rendering them politically intractable.

Solar geoengineering comes at a cost

Solar radiation management scenarios of two non-cooperative actors deploying stratospheric aerosol injection (SAI) can lead to a free-riding situation, or missing the climatic targets due to temperature oscillations induced by intermittency.

Ten years after the publication of The Ethics of Geoengineering: Perspectives from Romania, I revisit the ethical and epistemological questions surrounding climate intervention technologies. In the meantime, geoengineering has moved from being a speculative concept to becoming a central element in climate policy discussions. I argue that this shift has not been driven by transparent public debate or broad scientific consensus. Rather, it results from a deeper process of normalization that increasingly portrays techniques like Solar Radiation Management as rational and even necessary responses to the climate crisis. This framing is rooted in a technocratic worldview that prioritizes control, modeling, and predictive planning, often at the expense of ethical inquiry, democratic engagement, and respect for ecological complexity. I believe that the dominant assumptions shaping geoengineering foster a vision of governance where preparedness is mistaken for legitimacy, and responsibility is reduced to procedural compliance. As a result, critical questions about authority, knowledge systems, and the future we choose to pursue are frequently marginalized or deferred. In response, I advocate for a different ethical framework, one that emphasizes epistemic humility, justice across generations, inclusive co-design, and recognition of multiple ways of understanding the world. Geoengineering, in my view, is not a neutral technological fix but a manifestation of modernity’s drive to impose order in response to planetary uncertainty. An adequate ethical approach must go beyond measurements and institutional procedures to question the kind of planetary future we are creating, whose voices are included, and which values guide our decisions in times of crisis.

Abstract Corresponding with the accelerating crises of climate and biodiversity loss has been a call in contemporary environmentalism to think and act at planetary scales to address a planetary problem. One prominent proposal, stratospheric aerosol injection (SAI), would attempt to replicate the cooling effect of volcanic eruptions by tactically injecting reflective particles into the atmosphere in an attempt to reverse global warming. This article first constructs a new case for SAI on behalf of the wild, an idea that has appeared in passing within several influential arguments for solar engineering but has not received widespread endorsement. I then introduce the reader to Aldo Leopold’s land ethic and defend one interpretation that is supported by mainstream interpreters in the literature, drawing the reader’s attention to the important role that a human/nature parallel plays in Leopold’s moral reasoning and the value he places on preserving biodiversity. Then, I apply this framework to SAI and argue that it poses an intractable dilemma for ‘geoengineering for the wild.’ I provide a novel reading of Leopold’s famous essay “Thinking Like a Mountain” and argue it illustrates the importance of two distinct forms of intellectual humility in his thought. Then, I present the dilemma. It appears when one answers a simple question: is it better for SAI to “work” or “fail?” As I will discuss, this question is too simple, but it is revealing. I will argue in what follows that from a Leopoldian outlook both success and failure in solar geoengineering should deeply trouble us. This constitutes 'the climate engineer's dilemma.'

The urgent need for research governance of solar geoengineering

BackgroundClimate change is expected to reshape malaria transmission dynamics in tropical and subtropical regions. Stratospheric Aerosol Injection (SAI), a proposed solar geoengineering strategy to reduce global warming, could have unintended consequences for vector-borne diseases such as malaria. This study investigates how SAI, through the Stratospheric Aerosol Geoengineering Large Ensemble (GLENS-SAI) scenario, could alter malaria transmission patterns across seven South Asian countries—Afghanistan, Bangladesh, Bhutan, Iran, India, Nepal, and Pakistan—compared with an unmitigated warming scenario over coming decades.MethodsUsing the VECTRI malaria model, malaria transmission dynamics were simulated from 2020 to 2097 under two climate pathways: the GLENS-SAI simulations, designed to stabilize global temperatures at 2020 levels, and the high-emissions Representative Concentration Pathway (RCP) 8.5—the control scenario (CTRL), representing unmitigated climate change. The model incorporated climatic and demographic factors to simulate vector density, Entomological Inoculation Rate (EIR), and malaria cases. Spatial patterns were assessed using distribution maps, while temporal variability was examined through time-series analysis. Statistical comparisons employed regional averages, anomaly detection, and significance testing.ResultsThe findings reveal a redistribution of malaria transmission dynamics under the GLENS-SAI scenario, reflected in variations in vector density, EIR, and malaria cases. Compared to CTRL, the GLENS-SAI scenario reduces malaria transmission intensity across South Asia, though spatial heterogeneity persists. Significant declines in EIR are observed in India, Nepal, Bangladesh, northern Pakistan, southern Iran, and the Afghanistan-Pakistan border region, indicating the suppressive effect of the GLENS-SAI scenario on malaria transmission. However, localized increases in EIR are projected in southeastern Pakistan, western Afghanistan, north-central and eastern Iran, and northern Nepal. These shifts are likely driven by SAI-induced changes in temperature and precipitation, influencing mosquito survival and reproductive dynamics. Additionally, the annual malaria transmission cycle shortens in amplitude and duration across several endemic areas, suggesting a shift in seasonal transmission patterns and altered windows of disease risk throughout South Asia.ConclusionsWhile the GLENS-SAI scenario may reduce malaria transmission across much of South Asia, localized increases highlight the need for region-specific public health strategies. These findings underscore the importance of incorporating GLENS-SAI scenario impacts into malaria control planning to address spatially varied effects.

Abstract Solar geoengineering via stratospheric aerosol injection (SAI) poses an optimization problem. How exactly should aerosol be deployed to maximize its benefits while minimizing undesirable side‐effects, such as shifts in rainfall patterns? Previous work explored this problem using feedback control based on linear algorithms. Here, we investigate an alternative approach, which also naturally incorporates feedback. We let a reinforcement learning (RL) algorithm control the distribution of stratospheric aerosol concentration in an idealized global climate model (GCM). Within several dozen GCM simulations, RL learns to produce stable and plausible strategies. RL also learns that the optimal geoengineering strategy depends on the time when geoengineering is initiated, which we further explain using a simple energy‐balance model. Our results provide a first proof‐of‐concept that RL can identify promising SAI strategies.