A group of over 60 scientists and governance scholars from around the world is calling for a moratorium on the study and development of solar geoengineering — a potential strategy aimed at reducing greenhouse gas emissions. The group is promoting a non-use agreement, describing the technology as “ungovernable” in any fair way.

There’s two main ways to respond to the climate crisis. We can either reduce your emissions, which is what countries all around the world are doing (hopefully), or we can try something much more radical: tweaking the way solar rays hit the Earth.

Solar geoengineering is a mitigation strategy to reflect sunlight to cool the Earth. There are several ways to go about this, but the most popular approach involves injecting reflecting particles into the atmosphere to “dim” the sun.

This simulates what happens during volcanic eruptions when volcanoes emit particles into the upper atmosphere. The particles reflect sunlight and lead to cooling during their time in the stratosphere, which may be several years. Solar geoengineering would then mimic the effect of a volcanic eruption to lower Earth’s temperatures.

Researchers have been studying solar geoengineering for several years but the technique is still controversial, mainly because it’s impossible to contain its consequences to a single geographical region. For example, if the US decided to spray aerosols in the atmosphere, this could have effects on South America and Oceania.

“Solar geoengineering deployment cannot be governed globally in a fair, inclusive and effective manner,” the open letter reads, which can be seen here. “We therefore call for immediate political action from governments, the United Nations and other actors to prevent the normalization of solar geoengineering as a climate policy option.”

Risks and challenges

In a recently published commentary, researchers share three main concerns on solar geoengineering. First, they argue the risks of the emissions mitigation strategy are not yet properly understood and may never be fully known. Its impacts also vary from region to region, with uncertainties about the effects on agriculture, food and water provision, and weather patterns. 

Solar geoengineering can also threaten a country’s commitments to reduce their emissions, the letter reads, disincentivizing governments, businesses, and societies to reach carbon neutrality as soon as possible. It’s a distraction from real, reliable solutions, and the promise of a saving technology can also be an argument for climate denialists and lobbyists to delay decarbonization policies.

“The current global governance system is unfit to develop and implement the far-reaching agreements needed to maintain fair, inclusive, and effective political control over solar geoengineering deployment,” the researchers argue, claiming all the UN bodies are incapable of guaranteeing an equitable control over its deployment. 

Lastly, solar geoengineering deployment can’t be managed in a fair, inclusive, and effective way, according to the group of experts. Those able to deploy it would be basically making the decision for everybody. So governments and other actors should restrict their development and prevent it from becoming a climate policy option. That’s why they advocate for a non-use agreement, targeted against the use of the technology. 

The agreement should commit governments to five measures:

• prohibiting the use of national funds for solar geoengineering;
• banning outdoor experiments of the technology in areas under their jurisdiction;
• not granting rights for the technology;
• not deploying it if developed by third parties;
• objecting to its use as a mitigation option.

“Decarbonisation of our economies is feasible if the right steps are taken. Solar geoengineering is not necessary. Neither is it desirable, ethical, or politically governable in the current context,” the researchers wrote.

However, whether or not policymakers will heed researchers remains to be seen. We’ve seen time and time again, over the course of the climate crisis, researchers being ignored. With things like solar geoengineering, the stakes are getting higher — and mistakes will be more and more costly.