The European Union should  “proactively negotiate” for a global regime that governs controversial technologies designed to cool the planet – and push to prevent their deployment, its scientific advisors have said.

The recommendations from the EU’s Scientific Advice Mechanism mark the first time the bloc has received such advice on a highly divisive group of technologies known as “Solar Radiation Management” (SRM).

SRM technologies are designed to temporarily relieve the world from extreme heat by blocking some of the sun’s warming impacts. This could include pumping aerosols into the high atmosphere, spraying saltwater into clouds to brighten them, or even sending mirrors into orbit to reflect more sunlight away from the Earth.

These technologies wouldn’t tackle the root cause of climate change – namely rising heat-trapping greenhouse gas emissions – nor could they address the impacts of those emissions on ocean acidification for example.

“At best, they would reduce warming from solar radiation on a temporary and local scale,” the scientific opinion notes.

Risky strategy

It’s a risky strategy. SRM carries major uncertainties and wide-ranging risks that are poorly understood.

Deployment is “likely to bring substantial negative ecological and economic effects, including changing patterns of rainfall, impacts on ecosystems, a decrease in the security of food production and in the potential of solar energy,” the EU report warns.

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The EU doesn’t have an official position on SRM, although it “does not consider [it] as a solution”, according to a 2023 policy scoping paper, which describes the deployment of these technologies as “an unacceptable risk for humans and the environment”.

Last year, the EU’s then Green Deal chief Frans Timmermans requested advice from the union’s seven scientific advisors to help define a common position.

In response, the advisors urged the EU to prioritise reducing greenhouse gas emissions and focus on adapting to climate impacts as the main solutions to global warming.

The uncertainties associated with deploying SRM are inconsistent with Europe’s precautionary and “do no harm” principles, and decision-makers should agree an EU-wide moratorium, they concluded.

At the same time, SRM is gaining more attention as a potential cheap and fast solution to reduce overheating as the world barrels towards overshooting the 1.5C warming threshold above which scientists have warned of catastrophic climate change.

“Cooling credits”, which at least one company using SRM technology is already selling at small scale, should be banned from being used to meet international climate obligations, the advisors added.

Creating rules

Despite the potentially dangerous impacts of deploying SRM on a large scale, there is no international framework governing these activities.

A de facto moratorium was agreed in 2010 by members of the UN Convention on Biological Diversity, with exceptions for small-scale scientific research studies – but the decision isn’t legally binding and the United States is not party to the treaty.

The EU should take a leading role in negotiating a global governance system and push for the “non-deployment of SRM in the foreseeable future”, with exemptions for “limited outdoor research” that meet a set of conditions and risk considerations, the advisors argue.

Besides a ban on large-scale outdoor experiments, they recommend the creation of “clear ethical requirements” and guidelines for smaller research projects. Any public funding for SRM research should not replace financing for research on climate action, and scientific evidence for using the technology should be reassessed every five to 10 years, they added.

The European Commission has previously expressed support for discussions on a global governance framework, including for research. But recent attempts to find international consensus on how to regulate SRM activities have failed.

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