With global average temperatures tracking toward 1.8°C of warming and the 1.5°C Paris target effectively out of reach, a controversial category of climate intervention — long considered too politically toxic to discuss openly — is forcing its way onto the international agenda. Solar radiation modification (SRM), sometimes called the “Voldemort of climate policy,” involves large-scale technological interventions designed to reflect a small fraction of sunlight back into space and thereby lower global temperatures. A growing number of researchers now argue that a blanket taboo on studying these approaches is no longer defensible.
SRM encompasses several proposed techniques. The most widely discussed is stratospheric aerosol injection (SAI), which would release reflective particles into the upper atmosphere to mimic the temporary cooling observed after large volcanic eruptions. Other methods include marine cloud brightening — spraying microscopic particles into low-lying clouds to make them more reflective — and, more speculatively, space-based mirrors.
Proponents frame SRM not as a replacement for cutting emissions but as a way to limit temperature overshoot while decarbonisation continues. Critics raise serious objections: SRM does nothing to reduce carbon concentrations, its ecological effects are poorly understood, and there is a risk of “termination shock” — if deployment were ever halted abruptly, temperatures could spike rapidly. Recent research suggests a real-world example of inadvertent termination shock may already have occurred: when new international shipping regulations sharply cut sulphur dioxide emissions after 2023, the loss of that incidental cooling effect is thought to have contributed to the unusually strong warming spike that followed.
Internationally, SRM sits in a governance vacuum. A Swiss proposal for a coordinated research framework was put before the UN Environment Assembly in 2024, but member states could not reach agreement even on whether to regulate research. Japan and Saudi Arabia backed continued study; Pacific and African nations, concerned about risks to vulnerable regions, resisted any language that could be read as endorsing the practice. In the United States, the politics are especially volatile. Several Republican-led states have moved to criminalise SRM on the grounds that it is already being conducted covertly — a claim without scientific support — while some conservative think tanks promote it as a tool of national interest. NASA maintains an exploratory programme examining space-based reflective dust clouds, and entrepreneur Elon Musk has voiced support for SRM. Private ventures, including the US-Israeli startup Stardust, are already pursuing research outside any public oversight framework.
Australia has no formal policy on SRM research or deployment, though public funds have supported related work, notably the Reef Restoration and Adaptation Program’s marine cloud brightening trials over the Great Barrier Reef. Existing environmental law may cover small-scale experiments but does not address the risks of eventual large-scale deployment, and no dedicated ethics framework exists for the field. Researchers writing in The Conversation argue Australia, as a mid-sized trusted power, is well placed to help shape international norms — assessing domestic climate, agricultural, and ecological impacts of various SRM scenarios, and developing a public position before a foreign government or private actor forces the issue.
The researchers stop short of advocating deployment, but argue the case for responsible scientific research and open public deliberation is now compelling. As planetary tipping points — including polar ice retreat, Amazon dieback, and coral reef loss — draw closer, they contend the question is no longer whether SRM will be part of the global conversation, but who will shape that conversation and on what terms.