Solar Geoengineering in 2024: Rays of Hope, Clouds of Doubt

This post provides a comprehensive overview of Solar Geoengineering (SRM) in 2024, from funding and research breakthroughs to global debates, restrictions, media highlights, and more.

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1. SRM Funding Announcements

2. Top SRM Stories

3. Restrictions and Bans on SRM

4. Essential SRM Reads from 2024

5. Spotlight on SRM in Media

6. SRM Research Highlights

7. Personal Milestones

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.

The Advanced Research and Invention Agency (ARIA) announced $75 million in funding for researchers to explore ideas for artificially cooling the planet, including outdoor experiments to assess their feasibility.

The Simons Foundation committed $50 million over five years to solar geoengineering research, offering grants of up to $500,000 per year. The foundation particularly encouraged applications from scientists in the Global South, with a focus on modeling and lab studies. (Applications are now closed.)

Quadrature Climate Foundation, established in 2019 and funded through the proceeds of the investment fund Quadrature Capital, plans to provide $40 million for work in SRM field over the next three years.

SilverLining secured $20.5M from major climate foundations, including Quadrature, Pritzker, 2040, Spitzer Trust, and Casey & Family, to advance its core governance, equity, and engagement initiatives on Near-Term Climate Risk and Climate Intervention over three years.

UKRI and NERC launched a £10.5M, five-year funded research programme (2025–2030) to model large-scale impacts of solar radiation management.

The Simons Foundation funded 14 projects exploring Earth-cooling techniques through a new international research program, allocating up to $10 million annually over the next five years across all the projects.

Researchers from University of Exeter secured £750,000 to study geoengineering solutions (SAI and MCB) to curb global warming.

Climate Intervention Environmental Impact Fund (CIEIF) announced three $75,000 grants for innovative climate intervention projects, supporting EIA, impact modeling, and public outreach worldwide.

A team at the University of Cape Town – led by Degrees-funded scientist and research collaborator, Dr Christopher Lennard – have been awarded funding from The Rockefeller Foundation, to support the exploration of the development of an African Research Coalition on SRM.

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World Climate Research Programme launched a Lighthouse Activity on Climate Intervention Research.

Switzerland proposed first UN expert group on solar geoengineering, but after a few months U.N. delegates at UNEA-6 withdrew this motion.

University of Washington researchers conducted the first U.S. outdoor test of marine cloud-brightening tech, using Cloud Aerosol Research Instrument (CARI) to spray salt aerosols for reflecting sunlight.

The University of Chicago launched a Climate Systems Engineering initiative to study solar geoengineering and other Earth system modifications addressing the climate crisis. The program is currently hiring faculty.

The Degrees Initiative has launched a major expansion in SRM research, supporting nine teams of social scientists from Argentina, Bangladesh, Brazil, Ghana, India, Mexico, Pakistan, and the Philippines. This marks the first international SRM program exclusively for developing-country social scientists, focusing on the socio-political dimensions of the field.

Reflective launched an SAI simulator to enable policymakers, the media and public to explore regional effects of various Stratospheric Aerosol Injection deployment scenarios as compared to the impacts of continued warming.

The United States is building an early warning system that would detect potential attempts by any nation or actors to influence the Earth’s climate through solar geoengineering.

A team of scientists proposed it could launch a giant parasol in outer space within a few years to help solve the climate crisis.

John Moore, a glaciologist and geoengineering researcher at the University of Lapland, proposed to install gigantic 62-mile-long underwater curtains around the 'doomsday glacier' for a $50 billion Hail Mary to save it.

The World Business Academy proposed a plan for solar-powered autonomous catamarans to enhance marine cloud brightening. Equipped with advanced aerosol dispersion technology, the vessels feature expansive solar arrays for propulsion, navigation, and continuous operation, offering a sustainable, fossil-free solution for distributing sea salt particles across the oceans.

Planetary Sunshade Foundation team met with officials from the White House to propose a trillion-dollar parasol for the planet to limit global warming.

Members of Healthy Planet Action Coalition wrote an open letter to the IMO supporting maritime transport that cools the atmosphere while preserving air quality benefits.

UK startup Real Ice plans to use underwater drones to refreeze the Arctic, with CEO Andrea Ceccolini estimating annual costs at $10 billion to counter sea ice loss.

Andrew Lockley launched Solar Geoengineering Events Calendar, a community resource aimed at providing timely updates on events, conferences, webinars, funding opportunities, and job deadlines in the SRM field.

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Harvard researchers ceased a long-running effort to conduct a small geoengineering experiment (stratospheric controlled perturbation experiment (SCoPEx)) in the stratosphere, following repeated delays and public criticism.

U.N. delegates at the U.N. Environment Assembly (UNEA-6) withdrew the draft resolution calling for more research into SRM technologies. The motion was withdrawn after six revisions and a lack of consensus on the controversial topic.

In April, University of Washington scientists started outdoor testing a saltwater spraying machine for Marine Cloud Brightening in California. The city paused the experiment in May, citing health & environmental concerns— but outside consultants hired by the city later concluded the test doesn’t pose a measurable health risk to the surrounding community. On June 4, Alameda City Council votes to shut down MCB experiment, criticizing project's lack of transparency.

Rep. Tom Young of Washington Township has introduced Ohio House Bill 529 to ban the deliberate release of atmospheric pollutants for solar radiation modification (SRM), citing potential ecological and health risks. The bill proposes strict penalties, including fines and prison sentences, and mandates EPA oversight. Similar legislation has been enacted in Tennessee and proposed in a half-dozen other states like Florida, Kentucky and Pennsylvania.

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Evidence review report-Solar radiation modification (Scientific Advice Mechanism to the European Commission)

Ethical Framework Principles for Climate Intervention Research (AGU)

Frozen Arctic—Horizon scan of interventions to slow down, halt, and reverse the effects of climate change in the Arctic and northern regions: A UArctic Rapid Response Assessment (UArctic)

Implications for governance of Stardust’s activities in relation to Stratospheric Aerosol Injection (Janos Pasztor)

Partially counteracting climate change in the short to medium term: options globally and for Switzerland (Swiss Science Council)

Stratospheric Controlled Perturbation Experiment (SCoPEx) Advisory Committee-Final Report (SCoPEx)

Field Study of Controlled-Release Sea Salt Aerosol Plume (University of Washington)

ARIA Programme Thesis: Exploring Options for Actively Cooling the Earth (ARIA)

Learning from Weather Modification Law for the Governance of Regional Solar Radiation Management-Book (Manon Simon)

Solar Radiation Modification (SRM): Intractable Governance and Uncertain Science (German Environment Agency)

Policymakers’ FAQ: Climate Interventions (ICFG)

Insights Into Our Global Engagement Decision-making: Where We Go And Why? (DSG)

A global foresight report on planetary health and human wellbeing (UNEP)

Glacial Climate Intervention: A Research Vision (University of Chicago)

Accelerating Climate Intervention Research to Improve Climate Security (SilverLining)

Addressing Solar Geoengineering within the CBD Framework (SDG)

Near-term Climate Risk and Intervention: A Roadmap for Research and Decision-making (SilverLining)

Scoping Note on the State of Solar Radiation Modification (SRM) Research, Field Tests, and Related Activities (Co-Create)

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Solar geoengineering could start soon if it starts small-David W. Keith & Wake Smith (MIT Technology Review)

Someone is going to dim the sun, and it will be soon (Ben James)

Scientists Resort to Once-Unthinkable Solutions to Cool the Planet (The Wall Street Journal)

Not such a bright idea: cooling the Earth by reflecting sunlight back to space is a dangerous distraction (The Conversation)

NOAA gets dire warning about solar geoengineering (E&E News)

How rerouting planes to produce fewer contrails could help cool the planet ( MIT Technology Review)

How You Can Easily Delay Climate Change Today: SO2 Injection (Uncharted Territories)

The Best Way to Find Out if We Can Cool the Planet (The New York Times)

The hard lessons of Harvard’s failed geoengineering experiment (MIT Technology Review)

Countries failed to agree first steps on solar geoengineering at the UN. What went wrong? (Legal Planet)

Talking About Tipping Points-Developing response capability for a climate emergency (Harvard Magazine)

Startups want to cool Earth by reflecting sunlight. There are few rules and big risks (NPR)

The inadvertent geoengineering experiment that the world is now shutting off (MIT Technology Review)

Honest dialogue is needed to help build consensus around solar radiation modification technology (The Conversation)

This London nonprofit is now one of the biggest backers of geoengineering research (MIT Technology Review)

New discovery reveals that ocean algae unexpectedly help cool the Earth (Phys.Org)

The Science And Ethics Of Solar Geoengineering (Harvard)

Unilateral Deployment: Could a Single Country Change the Global Climate? (SRM360)

Environmental Group to Study Effects of Artificially Cooling Earth (The New York Times)

Is cloud brightening a sensible way to combat climate change? (Illuminem)

Conspiracy theories swirl about geo-engineering, but could it help save the planet? (BBC)

This Scientist Has a Risky Plan to Cool Earth. There’s Growing Interest (The New York Times)

Comment on Buying Time by David Gelles, New York Times, 1st August 2024 (David Keith)

From Meta CTO to climate tech investor: Mike Schroepfer on his big pivot—‘Schrep’ talks geoengineering, glaciers, and where he draws the line between climate philanthropy and investment (MIT Technology Review)

Reflections from a Member of the SCoPEx Advisory Committee (Legal Planet)

Andrew Ng’s new model lets you play around with solar geoengineering to see what would happen (MIT Technology Review)

Is This Climate Tech Start-Up Going Rogue? Make Sunsets' sulfur dioxide strategy has academics and NGOs fuming (IEEE Spectrum)

Geoengineering is worth the risk — provided we regulate it properly (Financial Times)

How solar geoengineering could disrupt wind and solar power (Carbon Brief)

Scientists have said that we can cool the planet back down. Now they’re not sure it will be so easy (The Washington Post)

Global warming is speeding up. Another reason to think about geoengineering (Economist)

Hacking the Planet Needs Guardrails and Guidelines (Bloomberg)

Reflecting on Solar Geoengineering and Biodiversity: Insights from CBD COP16 in Cali (DSG)

Experiments outside the lab come with new responsibilities (Science)

Neither climate laboratory nor knowledge vacuum: What’s at stake for the Global South in the debate around solar geoengineering research (Science)

Could SRM Be Weaponised? (SRM360)

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Here are some of the most viewed and widely discussed SRM research papers of 2024:

Marine emissions of methanethiol increase aerosol cooling in the Southern Ocean (Science Advances)

Methanethiol (MeSH) emissions, previously unexplored, significantly enhance sulfate aerosols and cooling effects over the Southern Ocean, improving climate model accuracy, finds Wohl et al.

Do small outdoor geoengineering experiments require governance? (Science)

Harvard's cancellation of the SCoPEx experiment underscores the need for a governance framework for solar geoengineering, with Jinnah et al. suggesting that standardized, centralized proactive research governance could help alleviate tensions.

Abrupt reduction in shipping emission as an inadvertent geoengineering termination shock produces substantial radiative warming (Communications Earth & Environment)

The 80% reduction in sulfur dioxide emissions from international shipping in 2020 has led to significant radiative forcing, potentially doubling the warming rate in the 2020s, according to Yuan et al.

G6-1.5K-SAI: a new Geoengineering Model Intercomparison Project (GeoMIP) experiment integrating recent advances in solar radiation modification studies (EGUsphere)

Visioni et al. proposed the G6-1.5K-SAI experiment to study solar geoengineering using improved scenarios and modeling techniques.

Demographics shape public preferences for carbon dioxide removal and solar geoengineering interventions across 30 countries (Communications Earth & Environment)

Sovacool et al. finds that support for climate interventions varies by demographics, with higher approval in the Global South and among younger, lower-income groups, while gender shows minimal influence.

Identifying the regional emergence of climate patterns in the ARISE-SAI-1.5 simulations (Environmental Research Letters)

Using machine learning, this study conducted by Labe et al. finds that stratospheric aerosol injection impacts regional temperatures within a decade, while precipitation effects remain harder to detect due to climate variability.

Three Pathways to Nonuse Agreement(s) on Solar Geoengineering (Ethics & International Affairs)

In this essay VanDeveer et al. argues for global governance to establish a nonuse norm for solar geoengineering, proposing civil society, regional, and state-led pathways to institutionalize it.

Hemispherically symmetric strategies for stratospheric aerosol injection (Earth System Dynamics)

Zhang et al. systematically compares different stratospheric aerosol injection strategies, finding that the choice of strategy significantly affects climate responses, with subtropical injections proving more efficient for cooling.

Kicking the Can Down the Road: Understanding the Effects of Delaying the Deployment of Stratospheric Aerosol Injection (Environmental Research: Climate)

Brody et al. assessed the consequences of delaying SAI for climate change mitigation, finding that a 10-year delay increases sulfur dioxide injection rates and alters ozone and temperature dynamics, though longer-term impacts remain uncertain.

Clouds dissipate quickly during solar eclipses as the land surface cools (Communications Earth & Environment)

This study by Trees et al. investigates how solar eclipses impact clouds and sunlight reflection, highlighting that neglecting cloud changes during an eclipse could result in inaccurate estimates of solar radiation reduction, offering valuable insights for geoengineering models.

Solar radiation modification challenges decarbonization with renewable solar energy (EGUsphere)

Baur et al. examines how SRM through stratospheric aerosol injections could reduce solar energy production, particularly impacting solar power generation in mid-latitudes and posing challenges for meeting future energy demands.

How Does the Latitude of Stratospheric Aerosol Injection Affect the Climate in UKESM1? (EGUsphere)

This study by Henry et al. assesses the impact of different latitudes for stratospheric aerosol injection, revealing that equatorial injections cause significant cooling imbalances, while subtropical injections (15° and 30° N/S) present a more efficient and balanced strategy.

Addressing the urgent need for direct climate cooling: Rationale and options (Oxford Open Climate Change)

In this paper, Baiman et al. argues for deploying large-scale climate cooling measures alongside emissions reductions and carbon removal to prevent further global warming, mitigate climate change disruptions, and support adaptation, with a focus on near-term action and regional interventions.

On thin ice: Solar geoengineering to manage tipping element risks in the cryosphere by 2040 (Earth’s Future)

Smith et al. explores the potential of using SAI at the poles to manage risks associated with climate tipping points, recommending infrastructure development and funding decisions by 2030 to respond effectively by 2040.

Impact of solar geoengineering on temperature-attributable mortality (Proceedings of the National Academy of Sciences)

Harding et al. evaluates solar geoengineering's potential to reduce temperature-attributable mortality, finding that it could prevent over 400,000 deaths annually while weighing the mortality risks of SG methods like sulfate aerosol injection, with benefits likely outweighing risks.

Substantial cooling effect from aerosol-induced increase in tropical marine cloud cover (Nature Geoscience)

This study by Chen et al. uses satellite observations of volcanic aerosols to show that marine cloud brightening could effectively mitigate global warming, highlighting the enhanced reflectivity from aerosols and the increased sensitivity of Earth's climate to radiative forcing.

Side Effects of Sulfur-Based Geoengineering Due To Absorptivity of Sulfate Aerosols (Geophysical Research Letters)

Wunderlin et al. shows that sulfur-based SAI could lead to significant climate cooling, but side effects like tropical stratospheric heating and regional climate changes can be reduced by disabling longwave absorption in aerosols.

Radiative forcing geoengineering causes higher risk of wildfires and permafrost thawing over the Arctic regions (Communications Earth & Environment)

Radiative forcing geoengineering methods, like SAI, MCB, and CCT, partially mitigate global warming but lead to higher Arctic temperatures and worsen extreme conditions compared to emission mitigation, according to a study by Müller et al.

Analysis of the global atmospheric background sulfur budget in a multi-model framework (Atmospheric Chemistry and Physics)

This study of sulfur species in global atmospheric aerosol models conducted by Brodowsky et al. reveals significant variability in model representations of the sulfur cycle, highlighting the need for further research to reduce uncertainties, especially for SAI scenarios.

Toward an evidence-informed, responsible, and inclusive debate on solar geoengineering: A response to the proposed non-use agreement (Wiley Interdisciplinary Reviews: Climate Change)

Parson et al. argues against a broad "non-use agreement" on solar geoengineering, advocating instead for an informed, inclusive approach to research and governance to ensure safe and equitable climate risk management.

Stratospheric injection of solid particles reduces side effects on circulation and climate compared to SO2 injections (Environmental Research: Climate)

This study by Stefanetti et al. finds that solid particles like alumina, calcite, and diamond for stratospheric aerosol injection are more effective than sulfur in reducing warming and minimizing side effects, especially in the Arctic.

Marine-cloud brightening: an airborne concept (Environmental Research Letters)

Claudel et al. proposes manufacturing NaCl nanoparticles for Marine Cloud Brightening via UAVs, offering a more efficient, cost-effective, and scalable alternative to autonomous ships, while highlighting increased governance risks.

Modeling 2020 regulatory changes in international shipping emissions helps explain anomalous 2023 warming (Earth System Dyanamics)

Regulatory changes to sulfate emissions from international shipping routes since 2020 have significantly contributed to the anomalous surface temperature increase in the summer of 2023, highlighting the need to consider short-lived climate forcers in future climate projections, according to Quaglia and Visioni.

Stratospheric Aerosol Injection could prevent future Atlantic Meridional Overturning Circulation decline, but injection location is key (Authorea Preprints)

Stratospheric Aerosol Injection may help mitigate the decline of the Atlantic Meridional Overturning Circulation (AMOC), but its effectiveness depends on the specific SAI implementation, particularly its latitude, finds a study conducted by Bednarz et al.

Uncertainties and confidence in stratospheric aerosol injection modelling: a systematic literature review (Oxford Open Climate Change)

This study by Määttänen et al. examines 60 peer-reviewed articles on Stratospheric Aerosol Injection, revealing diverse approaches to uncertainty quantification and communication, and underscores the challenge of conducting global, quantitative uncertainty assessments in SAI research.

Research criteria towards an interdisciplinary Stratospheric Aerosol Intervention assessment (Oxford Open Climate Change)

Tilmes et al. propose a comprehensive international assessment of Stratospheric Aerosol Intervention research, integrating technical, societal, and environmental considerations to evaluate its impacts, risks, and future directions.

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