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PRECONTEXT
In 2025, despite growing global awareness and rising investment in climate action, the state of the climate and greenhouse gas emissions continued to highlight a persistent gap between ambition and outcomes. According to the Global Carbon Budget 2025, global fossil CO₂ emissions rose by approximately 1.1% in 2025, reaching record levels of around 38 Gt CO₂ and pushing atmospheric concentrations to an annual average exceeding 426 ppm, more than 50% above pre-industrial levels. These emissions trends are translating directly into rising temperatures. Data from the Copernicus Climate Change Service and other agencies indicate that in 2025, the world experienced its third-warmest year on record. The last 11 years are the warmest ever recorded, and the average temperature from 2023 to 2025 has now risen more than 1.5 °C above pre-industrial levels, marking a critical threshold referenced in the Paris Agreement.
Meanwhile, the UNEP Emissions Gap Report 2025 finds that current national policies and pledges remain misaligned with pathways consistent with limiting warming to 1.5 °C, placing the world on a trajectory of approximately 2.3 °C to 2.8 °C of warming by the end of the century, depending on implementation. Together, these indicators point to a rapidly narrowing carbon budget and reinforce concerns that incremental progress is insufficient to alter the current warming trajectory.
The consequences of this trajectory are already becoming visible in economic and human terms. The Global Assessment Report on Disaster Risk Reduction 2025 indicates that average direct losses from climate-related disasters rose from approximately $70-80 billion per year between 1970 and 2000 to $180-200 billion per year during 2001-2020, with total costs exceeding $2.3 trillion annually when indirect and ecosystem impacts are considered. According to the charity Christian Aid’s 2025 annual assessment, the world’s top 10 climate-related disasters alone caused more than $120 billion in economic losses.
The human toll is rising as well. The Lancet Countdown on Health and Climate Change 2025 reports a 23% increase in heat-related mortality since the 1990s, reaching an estimated 546,000 deaths per year. Projections from the World Economic Forum suggest climate change could contribute to around 14.5 million additional deaths globally by mid-century under current trends.
These conditions have sharpened scientific and policy discussion around a broad portfolio of climate responses - deep mitigation and rapid emissions reduction, expansion of carbon dioxide removal (CDR) approaches, and rigorous, transparent research on solar geoengineering (SRM) and other climate intervention strategies, to manage both near-term risks and long-term stabilization goals.
This animation shows the expected impact of climate disasters on GDP from the year 2030 to 2100 (Source)
2025 SRM Year in Review
For those unfamiliar: Solar Geoengineering, also known as Solar Radiation Management (SRM), is a climate intervention technique that aims to reflect sunlight away from Earth to reduce global warming.
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Stardust, a US-Israeli startup, raised $60 million in a Series B round, bringing total funding to $75M, the largest venture investment to date for a company pursuing SRM. Backed by global investors, it plans controlled airborne experiments in April 2026 and aims for SAI deployment by decade’s end, pursuing government contracts. The company has also quietly lobbied the U.S. Congress for months, hiring Holland & Knight in early 2025.
The UK’s Advanced Research and Invention Agency (ARIA) awarded £45 million for 21 climate intervention projects from a £56.8 million programme budget. Five of these projects focus on “small-scale outdoor experiments” exploring Arctic ice thickening, MCB & SAI, together accounting for nearly half the total budget. The largest grant, £9.9M over 42 months, goes to the Centre for Climate Repair for research on re-thickening Arctic sea ice.
UK Research and Innovation’s Natural Environment Research Council (NERC) awarded £10 million to four new research projects under a five-year programme (2025–2030) to examine the risks, limitations, and trade-offs of SRM.
The Climate Systems Engineering initiative (CSEi) awarded over $7 million to 14+ interdisciplinary projects advancing climate systems engineering research and policy. Topics include SRM, CDR, glacial interventions, and governance and public perception.
The University of Chicago's Climate Systems Engineering Initiative secured a $5 million grant from the Quadrature Climate Foundation to advance SRM research.
Arête Glacier Initiative raised $5 million to improve forecasts of sea-level rise and explore the possibility of refreezing glaciers in place. It is also offering grants of $10,000-$250,000 to support research on catastrophic sea-level rise, including observational tools, data analysis, and glacier physics, with applications closing on 31 March 2026.
Reflective awarded $400,000 across eight research grants to study SAI near the poles and at lower, more practical altitudes, assessing feasibility, deployment risks, and impacts on health, ecosystems, and food systems. Grantees spanned four continents, with 30% based in the Global South.
The Environmental Defense Fund announced grants of $50,000-$300,000 for pilot research projects using natural analogs, such as volcanoes, wildfires, and changes in light, to better understand the potential impacts of Stratospheric Aerosol Injection on human well-being.
The Degrees Initiative funded five new SRM research teams in Vietnam, Cabo Verde, Republic of the Congo, Morocco and Jordan, enabling first-ever SRM studies in those countries and expanding its support to 27 countries.
In addition, The Degrees Initiative also renewed grants for 14 modelling teams first funded in 2023, allowing continued research across countries including Brazil, Malaysia, Cameroon, Chile, India, Thailand, South Africa, Benin, Pakistan, Ghana, Jamaica, Nigeria, Mali and Uganda.
Annelot Broerze, PhD researcher in Atmospheric Science & Climate Intervention at TU Delft received a Seed Fund grant for her project “Brighter Clouds, Cooler Future?” - an interactive installation designed to gauge public acceptance of Marine Cloud Brightening research.
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The IPCC appointed 664 authors from 111 countries to draft its Seventh Assessment Report (AR7). Among them, SRM experts including Danielle Visioni, Inés Camilloni, Helene Muri, and various others will contribute to Chapter 9, focused on Earth system responses and overshoot pathways. Several Degrees Initiative-funded SRM researchers are also contributing across multiple chapters.
The U.S. EPA formally requested information from Make Sunsets under the Clean Air Act after the company launched more than 120 SO₂ balloons as part of a private geoengineering effort. Make Sunsets responded, expressing openness to regulatory oversight and collaborating with governments and private partners to expand operations while promoting SAI as the “only realistic option” to curb global warming.
The Degrees Initiative convened the largest solar geoengineering conference to date in 2025, bringing 300 participants from 49 countries, with 47% from the Global South and 53% from the Global North, including 126 early-career researchers, to advance global dialogue on SRM science and governance.
The Alliance for Just Deliberation on Solar Geoengineering (DSG) launched “SRM Governance Horizons,” a new initiative exploring how political, financial, technological and socio-cultural forces shape SRM governance. The project will develop a readiness framework to support informed, inclusive decision-making before private or urgent interests dominate.
ESA announced two SRM research projects, ACtIon4Cooling and STATISTICS, aimed at improving understanding of aerosol–cloud interactions. Using satellite data, climate models, and natural analogues, the projects will assess approaches such as SAI, MCB, and CCT to reduce key climate uncertainties.
The Nuffield Council on Bioethics launched a project to identify the ethical considerations and health-related impacts associated with SRM and make recommendations for the governance of research and development. The project will be delivered in two phases, and findings will be published by early 2027.
The Planetary Sunshade Foundation launched a Research Network creating a public directory of global space-based sunshade research, highlighting peer-reviewed studies, funded projects, and technical work to improve visibility and coordination.
Reflective published a preliminary version of its Stratospheric Aerosol Injection Uncertainty Database, mapping key physical uncertainties and their potential consequences to help guide future SRM research priorities.
Reflective also launched the Reflective Cloud, a free, browser-based computing platform offering shared resources to support open, collaborative SAI research and cloud-based climate data analysis.
SRM360 launched several new public tools, including an SRM Outdoor Experiments Tracker covering completed, ongoing, planned, and cancelled field experiments; a Funding Tracker providing the first global overview of SRM funding flows; and a U.S. State Legislation Tracker monitoring laws referencing solar geoengineering or atmospheric climate modification.
The Navigate project, launched in April 2025 by researchers from NORCE & BCCR, CICERO, and the Norwegian Meteorological Institute to examine the climate system’s response to CDR and SRM.
US EPA Administrator Lee Zeldin released online resources to address public concerns about contrails and solar geoengineering, debunking chemtrail myths, explaining contrails, and noting that SRM techniques like SAI remain theoretical and are not in use.
A survey by Süddeutsche Zeitung, one of Germany’s largest national newspapers, asked around 300 climate scientists about solar geoengineering. Results show limited support for deployment, broader backing for continued research, and strong concern that geoengineering should not weaken efforts to reduce CO₂ emissions.
Similarly, a New Scientist survey of 120 researchers who contributed to the latest IPCC Assessment Report finds that many climate experts anticipate SRM deployment by 2100 if emissions continue unabated.
YouGov also conducted a UK poll finding that 31% support marine cloud brightening, 18% back space-based sunshades, and 16% support stratospheric aerosol injection, while 46% were unsure, with younger respondents showing greater openness.
The University of Chicago’s Climate Systems Engineering Initiative introduced its first cohort of six early-career research fellows for 2025-2027, who will work with faculty to advance interdisciplinary research on climate interventions, including carbon removal, SRM, and methods to slow glacial melt.
A University of Manchester and NCAS-led research project, REFLECT, was launched to examine whether marine cloud brightening could help cool the planet and reduce the risk of climate tipping points, while assessing feasibility, risks, and responsible testing.
Make Sunsets received its first U.S. patent for a balloon-based SO₂ delivery system and plans to openly license the technology, allowing stratospheric deployments of up to one tonne per year without restriction.
The Alliance for Just Deliberation on Solar Geoengineering (DSG) announced its 2025 Early Career Fellows, aiming to elevate Global South and underrepresented perspectives in SRM governance and strengthen more inclusive, justice-focused global policy debates.
DSG also launched a dedicated library of free Learning Resources on their website to serve as a central location for learning about solar geoengineering.
Reflective Earth has made available a Dekati Electrical Low Pressure Impactor (ELPI) to support SRM research, including MCB and SAI. The device measures aerosol particle sizes and can be requested by research teams with or without a trained operator.
The American Geophysical Union (AGU), the world’s largest association of Earth and space scientists, was awarded the Power of Associations Gold Award by the American Society of Association Executives (ASAE) for its efforts in promoting ethics in climate intervention research.
The documentary Plan C for Civilization screened in New York, exploring solar geoengineering through formal scientific research and controversial DIY cooling efforts, while raising questions about ethics, governance, and private involvement in climate intervention.
ETH Zürich researcher Sandro Vattioni won China’s 2025 Pineapple Science Award, the Chinese equivalent of the IgNobel Prize, for a study exploring whether diamond dust in the stratosphere could help cool the climate.
Elon Musk proposed on X a solar-powered AI satellite constellation system to regulate sunlight and curb global warming, reviving geoengineering debates, as critics warn of governance risks and reports suggest AI growth could accelerate climate change.
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Arctic Ice Project has ended operations, winding down a decade-long effort to test reflective materials to slow Arctic ice loss. The team said funding challenges, skepticism, and safety uncertainties make continued work impractical, though results and data will be published for others to build on.
Parties to the London Convention and London Protocol (LC 47 / LP 20) reiterated a precautionary approach to marine geoengineering including marine cloud brightening, warning that growing ocean-based CDR and SRM efforts could harm marine ecosystems.
African ministers at the African Ministerial Conference on the Environment (AMCEN20) reaffirmed their rejection of SRM, labeling it “dangerous” and unsuitable for climate policy. They endorsed a global non-use governance mechanism and urged prioritization of equitable climate finance and locally rooted adaptation strategies.
On the sidelines of UNEA-7, the Africa Group also launched a plurilateral dialogue toward a Solar Geoengineering Non-Use Agreement, seeking to prohibit funding, experimentation, patenting, and official promotion of SRM, building on the AMCEN20 decision.
In Europe, Germany reaffirmed its rejection of SRM as a climate policy option, citing risks and uncertainties. The UK government likewise reiterated opposition to SRM deployment while supporting research, public debate, and regulatory discussions. The UK Parliament also debated geoengineering following a public petition.
In the United States, lawmakers in around 35 states, as well as at the federal level (Clear Skies Act), have introduced bills to ban solar geoengineering (non-existent), but only Tennessee (SB2691), Florida (SB 56), and Louisiana (SB 46) have enacted bans into law, imposing strict penalties including fines and prison sentences. Similar bills have failed in around a dozen states, including Texas, Montana, South Dakota, and Michigan, and remain under consideration in others.
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Geoengineering: Assessing Risks in the Era of Planetary Security (Carnegie Endowment for International Peace)
Solar radiation modification (The Royal Society)
From Science to Policy: Navigating the Complexities of Emerging Climate Techniques in the Americas (ENG) - Multilateral Simulation Workshop on Solar Radiation Modification (DSG, IAI, The Degrees Initiative)
Global Tipping Points Report 2025 (Global Tipping Points)
Climate geoengineering: call for caution and rigorous supervision (French Academy of Sciences)
Degrees Global Forum on SRM - Conference Report (The Degrees Initiative)
Addressing Social Science Questions About Solar Radiation Modification (RFF)
How to Learn Everything You Need to Know About Climate Cooling (Inevitable & Obvious)
In support of geoengineering (The Guide to a Gigaton)
Solar Geoengineering Research: Next Steps for the Climate Movement - Workshop Outcomes Report (CCAN, DSG & EDF)
Strategic Foresight Report 2025 - Resilience 2.0: Empowering the EU to thrive amid turbulence and uncertainty (European Commission)
The UK and the Antarctic environment: Government Response (UK Parliament)
Capping Climate Change from Space: Technology Development and Climate Change for the SDGs (United Nations)
Solar Radiation Modification—Concepts, Risks and Governance of intervention in the global climate system through solar geoengineering (German Environment Agency)
Workshop Report: The Governance of Arctic Climate Interventions (Harvard Kennedy School)
Finalizing experimental protocols for the Geoengineering Model Intercomparison Project (GeoMIP) contribution to CMIP7 - Meeting Report (AMSO)
Solar Geoengineering, Aviation and the Future of Climate Control (Simpliflying)
How human-caused aerosols are ‘masking’ global warming (Carbon Brief)
What’s the Difference Between Adaptation and Geoengineering? (Inevitable & Obvious)
Solar Geoengineering: A conversation we cannot afford to ignore (Janos Pasztor)
The Compass for SRM: Collective Need Over Private Profit (DSG)
Contrails or Chemtrails? An Explainer for Dummies (Chris Martz)
Co-Create Case Studies of Solar Radiation Modification (SRM) Field Tests and Related Activities (Co-Create)
Climate interventions: research vs. deployment (Center for future generations)
Strategic Foresight Toolkit for Resilient Public Policy (OECD)
FAQ Spotlight: Doesn’t international law already prevent the deployment of Stratospheric Aerosol Injection? (CFG)
International Law and Marine Geoengineering (Robert C. Steenkamp)
Dimming the Sun: The Urgent Case for Solar Geoengineering (Thomas Ramge)
Geoengineering and Climate Change: Methods, Risks, and Governance (Edited by Martin Beech)
Shade - The Promise of a Forgotten Natural Resource (Sam Bloch)
The Long Heat: Climate Politics When It’s Too Late (Andreas Malm and Wim Carton)
UK scientists to launch outdoor geoengineering experiments (The Guardian)
Researchers quietly planned a test to dim sunlight. They wanted to ‘avoid scaring’ the public (Politico)
Failure to Communicate—Geoengineering could be crucial in the fight against climate change. But first scientists need to learn how to talk to the public about it (Science)
How one controversial startup hopes to cool the planet (MIT Technology Review)
Solar geoengineering startups are getting serious (MIT Technology Review)
The urgent need for research governance of solar geoengineering – Shuchi Talati (Physics Today)
Betting on climate failure, these investors could earn billions (E&E News by Politico)
Why the for-profit race into solar geoengineering is bad for science and public trust (MIT Technology Review)
The Guardian view on solar geoengineering: Africa has a point about this risky technology (The Guardian Editorial)
Response: We must not stop research on solar geoengineering (The Guardian)
Governing Sunlight Reflection: A Review of Global Efforts (Planetary Sunshade Foundation)
As Solar Geoengineering Enters its Startup Phase, Governments Must Address Emerging Security Risks (Just Security)
Out of a superhero movie: Companies are coming up with plans to block out the sun (Independent)
Chemtrails Aren’t Real. So Why Are Politicians Passing Laws About Them? (Rolling Stone)
Private companies have raised millions to block the sun. What could go wrong? (The Washington Post)
A Startup’s Bid to Dim the Sun (The New Yorker)
Mirrors in space and underwater curtains: can technology buy us enough time to save the Arctic ice caps? (The Guardian)
Floating wood could help us refreeze the Arctic seas (New Scientist)
Inside a new quest to save the “doomsday glacier” (MIT Technology Review)
Why we urgently need to talk about geoengineering (New Scientist)
The strange and totally real plot to blot out the sun and reverse global warming (E&E News by Politico)
Dimming the Sun Is a Terrifying New Industry (Bloomberg)
Systemic Climate Risks are Underpriced and Under researched (The ARC)
Geoengineering startup has been secretly lobbying Congress for months (Politico Pro)
Why geoengineering is no longer a complete taboo for scientists (New Scientist)
Solar geoengineering in wrong hands could wreak climate havoc, scientists warn (The Guardian)
Should private firms be involved in cooling the planet? (Legal Planet)
The Science and Politics of Geoengineering with Ted Parson (Nate Hagens)
How Hard Is It to Dim the Sun? (State of the Planet)
Can we cool the planet by painting rooftops white? (Science Norway)
The promises and perils of geoengineering (David Suzuki Foundation)
How pie-in-the-sky conspiracies distract from climate dangers (New Scientist)
Sunscreen for the planet (Works in Progress)
Rich nations reap most funding for geoengineering research (E&E News)
Refreeze the Arctic? Scientists split over polar geoengineering (Politico Pro)
How the little-known ‘dark roof’ lobby may be making US cities hotter (The Guardian)
Unsubstantiated 'chemtrail' conspiracy theories lead to legislation proposed in US statehouses (Washington Post)
Africa must lead the governance of solar radiation management (Nature Climate Change)
Reduce, remove, reflect — the three Rs that could limit global warming (The Conversation)
Could a giant dam save the Atlantic currents that keep Europe warm? (Science)
Turns Out Air Pollution Was Good for Something (The New York Times)
Preserving Earth’s Reflectivity: Supplementary Comments on “A Responsible Way to Cool the Planet” (David Keith)
How to work towards a more responsible approach to preventing climate risks and promoting research on climate interventions (Operaatio Arktis)
This conspiracy theory used to be niche. Now it’s embraced by GOP lawmakers (Washington Post)
Geoengineering could avoid climate tipping points, but not if we delay (New Scientist)
The UK’s gamble on solar geoengineering is like using aspirin for cancer (The Guardian)
Response: Climate research into cloud barriers or Arctic refreezing is worth funding (The Guardian)
Britain’s enemies could dim the sun and weaponise weather (The Telegraph)
Why a Global “Moratorium” on Solar Radiation Management Deployment Should Get a Chilly Reception (Just Security)
The Politics of Geoengineering Are Getting Stranger (Legal Planet)
The Risky Climate Weapon Whose Time May Have Arrived (Bloomberg)
Geoengineering quantified: Heat is deadlier than air pollution (cipher)
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Here are some of the widely discussed SRM research papers of 2025:
Siegert et al. evaluated several proposed polar geoengineering methods, concluding that they would be infeasible, environmentally risky, “unimaginably expensive,” and a “dangerous” distraction from decarbonization. The authors advised against continued research into these interventions, sparking wide debate within the research community.
In response, Frontiers published multiple commentaries presenting contrasting views - from Mike Hulme supporting the paper’s conclusions, to Frans Berkhout emphasizing governance and policy complexities, Aarti Gupta’s call for an international non-use agreement on solar geoengineering, Sophie Crump’s focus on integrating Inuit perspectives into geoengineering policies, and John Moore’s case for continued geoengineering research under a “compassionate harm-reduction” framework. The paper inspired an open letter signed by over 100 scientists advocating responsible investigation of climate intervention approaches. Frontiers in Science also hosted a live discussion with the lead authors of this paper.
Yu et al. finds that injecting sulfur aerosols at 50 km, rather than the conventional 25 km, could reduce side effects, enhance cooling, speed ozone recovery, and preserve more Arctic sea ice.
He et al. propose using absorptive aerosols in the upper stratosphere to weaken the greenhouse effect, finding idealized models suggest this approach could reduce global temperatures far more efficiently per unit aerosol than conventional scattering-based SAI.
Bronsther & Xu challenge SRM as low-cost, estimating SAI could cause $0-$809B/year in collateral damages, with Marine Cloud Brightening likely higher, highlighting that despite <$10B/year technical costs, geopolitical, governance, and termination risks complicate comparisons with large-scale CDR.
Horton et al. find that a large-scale stratospheric aerosol deployment could technically be executed by only a few states, with the US and China being decisive actors, and argue that their alignment will strongly shape deployment likelihood and global impacts.
Surprise et al. argue that profit-driven solar geoengineering reflects the risks of market-based climate governance, warning that unregulated private ventures and “cooling credits” could undermine mitigation and call for stronger regulation or bans.
Clark warns that solar geoengineering risks creating policy “addiction,” potentially slowing emissions cuts despite claims it won’t delay mitigation.
Nielsen analyzes SAI through a U.S.–China security lens, finding that both could deploy it unilaterally, but cooperation yields better outcomes, may reduce tensions, and benefits policymaking amid great-power rivalry.
Talati et al. argue that solar geoengineering suffers from a transparency deficit, warning that opaque private experiments undermine public trust and calling for open research, disclosure of funding, and stronger governance to ensure legitimacy.
CESM simulations show that SAI lowers many tipping-element risks, with high-latitude injections favoring the northern cryosphere, low-latitude aiding tropical systems, and multi-objective SAI performing best, though trade-offs for Antarctica and the Sahel remain, Zhao et al. report.
HiLLA-SAI could provide substantial polar-focused cooling using existing large aircraft like the Boeing 777F, offering a feasible early-stage SAI deployment option, per Duffey et al.
Columbia University study by Hack et al. warns that SAI’s practical limits (engineering, supply, and governance) could make solid aerosols less effective, costlier, and riskier than models suggest.
Stratospheric Aerosol Injection could enhance cloud reflectivity through “diffusion-brightening,” increasing albedo by ~10% beyond direct aerosol effects, Gristey and Feingold report.
Clark et al. report that SAI may worsen protein declines in key crops by blocking warming-driven offsets, especially in malnutrition-prone regions.
Morrison et al. find that SAI offers limited benefits for luxury crops like wine grapes, coffee, and cacao, as it cools temperatures but cannot stabilize critical rainfall and humidity, leaving most producers exposed to yield and economic risks.
Antoan et al. find that balanced information on SRM does not reduce support for decarbonization and can increase climate urgency, suggesting moral-hazard concerns shouldn’t hinder responsible research communication.
Using interviews, focus groups, and a national survey, Buck et al. find that the US public shows more opposition than support for solar geoengineering research, with 20.6% believing the U.S. is already modifying the atmosphere. The authors frame this not simply as misinformation, but as “para-environmentalism.”
Using a conjoint experiment with 2,123 U.S. voters, Magistro et al. find that partisan alignment with the messenger shapes trust and support for solar geoengineering more than message framing, underscoring challenges in depolarizing climate debates.
SRM involves complex biophysical and sociopolitical risks that differ by method, and Wiener et al. propose a multi-risk framework to compare SRM, GHG mitigation, and adaptation, recommending global assessments and transparent monitoring for coordinated governance.
Baiman argues that only urgent near-term deployment of direct climate cooling alongside rapid emissions cuts can reduce climate harm quickly enough to avoid tipping points, as mitigation and carbon removal alone act too slowly in the near term.
Hussain et al. find SAI under GLENS generally reduces malaria in South Asia, though localized increases persist, highlighting the need for targeted public health planning.
Cheng argues that while SRM patents are currently allowed under international law, their dual climate benefits and risks warrant integrating ex ante risk assessment into a dedicated SRM patent regulatory framework.
Adding coarse calcite particles in “Stratospheric Aerosol Scrubbing” can cut stratospheric aerosols by 30-40% and reduce SAI cooling by ~30%, Crawford Jones et al. report.
Patrick finds that geoengineering debates highlight unknown risks, justice, and governance concerns, and using lessons from COVID-19 responses, he argues for strategic partnerships, alignment with community needs, ethics, and robust monitoring for future solar geoengineering engagement.
Sovacool et al. find that European public perceptions of carbon removal and solar radiation management vary widely, shaped by familiarity, trust, and climate attitudes, highlighting the need for inclusive, context-sensitive policies to avoid societal backlash.
Bahlmann et al. develop an 18-criteria framework to assess and guide sustainable space-based sunshades, highlighting key technical, social, and environmental gaps for safe and effective climate mitigation.
Bellamy reviews limited societal evaluations of space-based geoengineering, highlighting concerns about risks, governance, cost, feasibility, and participation, and argues for research and governance approaches that integrate societal values to responsibly advance climate interventions beyond Earth’s atmosphere.
Harrison et al. present an effervescent nozzle design for Marine Cloud Brightening that produces ∼1.73 × 10¹² CCN/s, showing that scaling to 10¹⁵ CCN/s for outdoor experiments is technically feasible and practical for research vessels.
Bednarz et al. find that Northern Hemisphere SAI can help stabilize the AMOC by modifying North Atlantic heat flux and density, while Southern Hemisphere SAI has little effect, highlighting the importance of deployment design and process understanding.
Doherty et al. propose a framework for SRM field studies that links experiment scale to objectives, emphasizing controlled tests to assess efficacy and risks, using marine cloud brightening to guide science and governance.
Li et al. report that large wildfires can inject smoke into the upper atmosphere, where cloud-processed, unusually large particles persist for months and enhance radiative cooling by up to ~36%, suggesting climate models may underestimate the cooling impact of increasingly frequent pyroCb events.
Carabajal et al. find that weak governance in Latin America and the Caribbean, highlighted by the unauthorized 2023 Make Sunsets release in Mexico, fosters mistrust and ethical concerns, underscoring the need for participatory, transparent SRM governance including LAC voices globally.
Coco et al. propose the preliminary design of a $10M precursor mission for a Planetary Sunshade System at the photo-gravitational point. A 12U CubeSat with a 400 m² solar sail would test shielding, solar sailing, and autonomous control for future solar geoengineering.
O’Loughlin and Visioni propose heuristics - rigor, safety, usefulness, and transparency - for dynamically evaluating small-scale solar geoengineering field experiments within the broader context of climate modeling and responsible research.
Boyer et al. unveil the surprising impact of penguin guano (Adélie colonies) on Antarctic climate regulation. The ammonia aerosols emitted from these colonies play a crucial role in cloud formation, which in turn reflects solar radiation by up to 15% and helps cool the region.
A global survey of 30,000+ people across 30 countries reveals how emotions about climate change shape perceptions of and support for climate intervention technologies, Baum et al. report.
Felgenhauer et al. propose a risk-risk framework to compare SAI against non-SAI scenarios, outlining four key steps to assess impacts. An initial analysis highlights challenges and suggests ways to improve decision-making in climate risk management.
Vattioni et al. find that solid alumina and calcite aerosols could reduce stratospheric warming and diffuse radiation compared to sulfate SAI, with limited ozone impacts at −1 W/m² forcing, but stress large uncertainties and the need for further laboratory research.
Using machine learning, Zhang et al. estimate that the IMO2020 shipping sulfur regulation caused a +0.074 ± 0.005 W m⁻² radiative forcing from cloud changes, showing aerosol reductions can accelerate warming but are difficult to detect amid natural variability.
Using 3-D radiative transfer modeling, Lemon et al. find that sky whitening from sulfate SAI at −2 W m⁻² would be undetectable for about half the global population, with visible changes mainly during twilight and smaller effects from diamond aerosols.
Measurements show that deploying reflective hollow glass microspheres could cool the Arctic and slow sea-ice loss, countering claims of warming based on overly high absorptance assumptions, Strawa et al. argue.
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