Not a risk worth taking: Solar geoengineering could put India's monsoon at risk

Waltham: Massachusetts: We're currently experiencing one of the most severe and widespread global heatwaves on record. Such extreme weather events are often cited as justification for considering solar radiation modification (SRM), a.k.a. solar geoengineering.

UNEP defines SRM as 'a set of speculative methods designed to reflect sunlight and temporarily cool the Earth'. Climate models suggest that SRM could reduce global temperatures. But deploying it on a climatically meaningful scale would require an unprecedented logistical effort.

According to the Royal Society, achieving roughly 1° C of cooling could require around 1,800 high-altitude aircraft flights per day, each carrying about 15 t of aerosol material for injection into the stratosphere. Sustaining such an intervention could require an aviation operation comparable to the daily flight capacity of about three Heathrow-sized airports for decades.


SRM also has important limitations. While it may reduce marine heatwaves in some regions, it could intensify them elsewhere. More fundamentally, SRM does not address the underlying causes of climate change. It would neither reduce fossil fuel-related air pollution, which carries a substantial public health burden, nor halt ocean acidification driven by rising atmospheric CO₂ concentrations. There is also concern that the prospect of a technological climate intervention could weaken political incentives for rapid emissions reductions, creating a moral hazard that prolongs dependence on fossil fuels.

Beyond these limitations, SRM poses significant environmental and ecological risks.

Injecting sulphur-containing compounds into the stratosphere could delay the recovery of the Antarctic ozone layer. Sulphate aerosols may also contribute to acid deposition, with potential consequences for ecosystems and human health, although the magnitude of these effects remains uncertain.

SRM could also weaken the global hydrological cycle, reducing average precipitation even as regional effects vary considerably. Its impacts on rainfall are among the greatest scientific uncertainties surrounding the technology.

Studies by Indian climate scientists suggest that different SRM deployment strategies could produce contrasting outcomes: some may strengthen atmospheric circulation, while others could suppress rainfall and create drier conditions across large parts of India.

There is little need to emphasise how profoundly any disruption to, or increased uncertainty in, the Indian monsoon could affect the country's economy and society. Less widely appreciated, however, is that the Afro-Asian summer monsoon - which underpins the water and food security of more than 2 bn people - is among the most difficult components of the climate system to model accurately. Future projections of monsoon precipitation, therefore, remain highly uncertain, and SRM could further complicate those projections.

Socioeconomic consequences of SRM could also generate geopolitical risks. Monsoon failures or catastrophic flooding in South Asia could be blamed - rightly or wrongly - on SRM deployment, potentially heightening regional tensions.

Yet, the most consequential strategic competition is likely to centre on the world's two leading powers, the US and China, whose technological capabilities and geopolitical influence make them the most plausible protagonists in any future contest over SRM deployment or governance.

The US could, in principle, deploy SRM unilaterally using its extensive network of military bases and airfields. Pentagon has identified geophysical and environmental conditions as factors that can shape national security and military operations, while US researchers are developing systems to detect potential solar geoengineering activities. Meanwhile, Israeli-American company Stardust has announced plans to commercialise SRM technologies. The company is led by Yanai Yedvab, a former deputy chief scientist at Israel's Atomic Energy Commission.

These developments underscore that SRM is increasingly intertwined with questions of strategy, security and global governance. Recognising these challenges, an international group of governance scholars has proposed a Solar Geoengineering Non-Use Agreement, arguing that existing international institutions are ill-equipped to develop and enforce governance arrangements that are equitable, inclusive and politically legitimate.

Calls for greater restraint have also gained traction across the developing world. Around 60 countries, including those represented at the 2025 African Ministerial Conference on the Environment, have expressed concern over expanding advocacy for solar geoengineering and have supported a non-use agreement or stronger international regulation.

By supporting efforts to democratise governance of SRM, Indian policymakers, academics and civil society can help ensure that decisions about a technology with planetary consequences are not determined solely by the interests of a few powerful states.

The writer is professor, environmental studies, Brandeis University, US