The Controversial Frontier of Climate Engineering
Solar geoengineering, also known as Solar Radiation Management (SRM), represents one of the most controversial proposed responses to climate change. As global temperatures rise and traditional mitigation efforts appear insufficient, some researchers propose technologies that could artificially cool the planet by reflecting sunlight back into space. However, these proposals have sparked intense debates about ethics, risks, and governance that extend far beyond scientific considerations.
Understanding Solar Geoengineering Technologies
Solar geoengineering refers to proposed approaches to cool Earth by reflecting solar radiation back to space. Stratospheric Aerosol Injection (SAI), the most studied method, involves releasing sulfur dioxide or reflective particles into the stratosphere at 20-25 km altitude, simulating volcanic eruptions like Mount Pinatubo in 1991, which cooled global temperatures by 0.5°C. Marine Cloud Brightening (MCB) increases cloud reflectivity by spraying seawater droplets, while space-based approaches involve placing mirrors or reflective particles between the sun and earth.
While these technologies appear potentially effective, inexpensive and technologically feasible, they would pose serious environmental, ethical, and governance challenges.
The SCoPEx Controversy: A Case Study
The Stratospheric Controlled Perturbation Experiment (SCoPEx), developed by Harvard University, represents the most prominent attempt at outdoor solar geoengineering research. SCoPEx aimed to spray water, chalk and sulfur particles from a high-altitude balloon to measure how effectively particles block sunlight and track atmospheric effects.
However, the project faced overwhelming opposition and was cancelled in March 2024. Just before the planned 2021 launch in Sweden, the government canceled the test due to resistance from environmental groups and the Indigenous Sámi Council. Harvard professor Frank Keutsch stated he “learned important lessons about governance and engagement throughout the course of this project.”
The experiment became a “proxy for a kind of debate about whether solar geoengineering research should move forward,” ultimately demonstrating the complex challenges facing such projects.
Indigenous Rights and Environmental Justice
The Sámi Council’s opposition highlighted critical issues around consent and environmental justice. Solar geoengineering “is a technology that entails risks of catastrophic consequences, including the impact of uncontrolled termination, and irreversible sociopolitical effects that could compromise the world’s necessary efforts to achieve zero-carbon societies,” the Council wrote. “There are therefore no acceptable reasons for allowing the SCoPEx project to be conducted either in Sweden or elsewhere.”
Their concerns addressed both technical risks and governance processes, criticizing the lack of engagement and dialogue. This exemplified broader concerns about how geoengineering could impact Indigenous communities and whether these communities have meaningful voice in decisions.
Ethical Dilemmas and Moral Hazard
Solar geoengineering raises profound ethical questions beyond environmental concerns. The primary concern is “moral hazard”—the danger that these technologies become an excuse to slow emissions reductions and delay transition to low-carbon economy. This can create a false sense that technological quick-fixes could tackle climate crisis, deflating pressure to rapidly phase out fossil fuel production.
Global equity poses additional challenges. Computer models suggest SAI would produce significant negative impacts disproportionately affecting the Global South, potentially endangering food and water sources for two billion people and causing severe droughts in Africa and Asia.
Scientific Uncertainties and Environmental Risks
Despite potential benefits, significant uncertainties remain. Solar geoengineering could reduce temperatures and limit climate tipping points but wouldn’t address root causes like rising CO2 concentrations or consequences like ocean acidification.
Termination Shock: The most concerning risk involves continuous deployment requirements. Once started, aerosol release would need to continue for hundreds or thousands of years. Sudden cessation would cause rapid temperature increases from accumulated CO2—a “termination shock” with devastating consequences.
Ozone Depletion: Certain particles could further damage the ozone layer, increasing harmful ultraviolet radiation.
Weather Pattern Changes: Solar geoengineering could significantly alter global weather patterns, potentially disrupting monsoons and climate systems upon which billions depend.
Governance Challenges
The Royal Society concluded that “The greatest challenges to the successful deployment of geoengineering may be the social, ethical, legal and political issues associated with regulation, rather than scientific and technical issues.” Currently, no comprehensive multilateral governance framework exists for research or deployment oversight.
This gap is concerning because of global effects and relatively low costs, meaning solar geoengineering might be implemented by individual states or non-state actors contrary to international wishes. Solar geoengineering, if weaponised, has the potential to deepen global inequality and escalate conflicts worldwide, as dominant nations could deploy technology potentially harming other regions.
Policy and Scientific Community Responses
Regulatory responses have been fragmented. Over 16 US states introduced solar geoengineering bans in early 2025, with Tennessee passing legislation in 2024. Germany’s Environment Agency called for global bans citing environmental and ethical risks.
The scientific community remains divided. Over 500 academics from 60+ countries signed an open letter advocating international agreements prohibiting solar geoengineering use. Frank Biermann noted: “The complete risks of eventual SRM deployment are unknowable, and there are at present no plausible global governance mechanisms to deal with such planetary-scale intervention technologies.”
However, others advocate “responsible research” with meaningful Global South and Indigenous participation under robust governance frameworks.
Public Opinion and Industry Interests
US surveys show more public opposition than support for research, with 20% believing the government currently uses atmospheric chemicals for climate purposes. This highlights challenges of public deliberation amid misinformation about weather modification.
Funding sources raise ethical concerns. SCoPEx received support from Bill Gates, venture capitalists, and organizations with military ties. Private companies like Make Sunsets have conducted unauthorized experiments, leading Mexico to announce bans on such activities.
The Path Forward
The future remains contested. Advocates argue society must understand all potential climate responses given mitigation inadequacy. Critics contend research creates deployment pressure and diverts resources from emissions reduction.
Some propose middle-ground “responsible research” approaches including: priority scientific and ethical questions; international scope with Global South and Indigenous participation; and robust governance with transparency and equity guidelines.
Many experts argue international governance mechanisms must precede large-scale research, addressing decision-making, risk management, and harm mitigation.
Conclusion: Planetary-Scale Ethical Dilemmas
Solar geoengineering represents unprecedented governance and ethical challenges. While theoretically offering climate risk reduction, it poses challenges for global governance, environmental justice, and democratic decision-making.
The SCoPEx experience demonstrates technical feasibility alone is insufficient for controversial interventions. Social, ethical, legal and political challenges may prove the greatest barriers, as predicted by the Royal Society.
As climate impacts intensify, solar geoengineering debates will continue evolving. However, SCoPEx and broader opposition suggest any path forward must prioritize robust governance, meaningful community participation, and serious consideration of alternatives.
The stakes are planetary, and today’s decisions about solar geoengineering research and governance will shape humanity’s climate relationship for generations. Whether it represents necessary climate response or unacceptable risk may depend less on technical capabilities than on developing just, inclusive governance frameworks for planetary-scale interventions.
Society must ensure voices of those most vulnerable—Indigenous communities, Global South nations, future generations—are centered in decision-making. Only through inclusive, democratic deliberation can we navigate the profound ethical terrain solar geoengineering represents.
