As planetary tipping points loom, scholars and policymakers are weighing the once-taboo field of solar radiation modification, or SRM, as a potential complementary measure to cool the planet while emissions reduction efforts continue.
The global climate policy landscape is shifting as the international community confronts the reality of missing the 1.5°C global warming target. Strategies that were once dismissed as unthinkable or dangerously hubristic are gaining traction. While climate mitigation—reducing or preventing greenhouse gas emissions—remains the core response, carbon dioxide removal and climate adaptation have steadily moved from the fringes into mainstream policy. Now, a similar reckoning is underway regarding solar radiation modification (SRM), a set of high-stakes interventions designed to reflect a small fraction of incoming sunlight back into space.
What is Solar Radiation Modification and Why Is It Controversial?
Often referred to in policy circles as climate stabilisation
, SRM encompasses several proposed large-scale technologies. These include space mirrors—satellites equipped with expansive reflective surfaces—and cloud brightening, which involves spraying microscopic particles into clouds to enhance their reflectivity. The most widely discussed technique is stratospheric aerosol injection (SAI), which would release reflective particles into the upper atmosphere to mimic the natural cooling effects observed after major volcanic eruptions.
Yet the subject remains so politically toxic that it is frequently labeled the Voldemort of climate policy
. Critics argue that SRM treats symptoms rather than causes because it does nothing to limit underlying carbon emissions. Opponents also warn that a potential technological fix could weaken political resolve to decarbonize, while the ecological consequences of deployment remain deeply uncertain. Furthermore, researchers point to the profound risk of termination shock
—an abrupt and catastrophic temperature spike if SRM deployment were suddenly halted.
That risk may already be manifesting in unexpected ways. Scientific research suggests the strong warming experienced since 2023 is likely a case of inadvertent termination shock. When new fuel regulations reduced sulphur dioxide emissions from international shipping, the rapid temperature rise that followed revealed that shipping pollution had incidentally been acting as a planetary cooling shield.
The Policy Vacuum and Global Divisions
Despite its growing prominence, SRM currently exists within a stark international and domestic policy vacuum. Some scholars continue to advocate for a total ban on both research and deployment, arguing that such technologies amount to playing God with nature. However, other experts counter that a research ban is no longer tenable as the world edges closer to dangerous tipping points, including polar sea ice retreat, the dieback of the Amazon rainforest, and widespread coral reef loss.
Governments remain deeply fractured on the issue. When the UN Environment Assembly discussed a Swiss proposal for SRM research in 2024, member states failed to reach a consensus on whether or how to regulate the field. Countries such as Japan and Saudi Arabia pushed to keep research channels open, whereas vulnerable Pacific and African nations strongly opposed any language that could be interpreted as endorsing the practice.
In the United States, the politics surrounding SRM are particularly volatile. One faction of Republicans rejects climate change science entirely while simultaneously displaying such intense suspicion of weather modification that several Republican states have criminalized it. Conversely, certain think tanks champion SRM as a tool to protect American Weather Sovereignty
. While NASA maintains an exploratory program investigating space-based reflective dust clouds, the Trump administration has not taken a definitive stance.
Private Actors and Regional Experiments
Without structured oversight, private entities and independent ventures are stepping into the regulatory void. Elon Musk has publicly expressed support for SRM, and private groups such as the US-Israeli startup Stardust are pursuing research without public accountability. Analysts warn that leaving SRM to self-interested actors poses significant geopolitical and environmental hazards.
Domestically, countries are taking varied approaches to related atmospheric and marine interventions. Australia maintains no official policy on SRM research or deployment, yet federal funding has supported targeted local projects such as the Reef Restoration and Adaptation Program (RRAP), which has trialled marine cloud brightening research over the Great Barrier Reef. While existing environmental laws can manage small-scale local trials, legal frameworks are entirely unequipped to govern the planetary risks of eventual deployment.
