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May 2025 Update

Dear ,

The 2025 Degrees Global Forum – the largest conference to date on SRM – assembled researchers, NGO representatives, policymakers, thought leaders, and journalists from around the world to discuss the scientific, social, and political dimensions of SRM. If you missed our live coverage of the event, you can catch up on the highlights through our Degrees Daily Archive. And don’t miss Trisha Patel’s perspective below, based on her closing speech at the Forum.  

Following ARIA’s Climate Cooling programme announcement earlier this month, we’re seeing significant media attention to SRM funding – with several outlets citing our new Funding Tracker. 

And two new academic papers present significant findings related to stratospheric aerosol injection deployment: Duffey and colleagues suggest that SAI is feasible with existing aircraft, and Horton and colleagues find that only the US and China would have the capacity to deploy SAI unilaterally.  

Those stories and more below. 

-The SRM360 Team

New From SRM360

SRM Funding Overview

Funding for SRM has risen sharply in recent years, with most funding originating in and being spent in the Global North. We found that half of the funding for SRM comes from philanthropic sources, with individual philanthropic organisations outspending most nations. While we found no evidence of fossil fuel funding, anonymous sources and incomplete data raise questions. Explore these key takeaways in our SRM Funding Overview.

In Conversation

SRM Academic Highlights

Getty Images. Credit: Puneet Vikram Singh

How might SRM affect rainfall in Southeast Asia? 

Feng et al. used computer models to compare the impacts of different SRM strategies on rainfall in Southeast Asia. The group concluded that SRM could decrease extreme rainfall risks across most of the region, but SAI’s effects on extreme rainfall were uneven, putting some areas at more risk.

SAI is feasible with existing aircraft 

At high latitudes, the stratosphere starts closer to the ground and existing aircraft can reach it. A new study by Duffy et al. found that SAI implemented at lower altitudes could produce a substantial cooling effect, though would be less efficient than higher altitude deployments, increasing negative side effects such as acid rain.

Only China and the US could deploy SAI unilaterally

In a recent analysis, Horton et al. determined that only China and the US would have the capacity and geopolitical power to conduct unilateral “Planetary, Large-scale, Uninterrupted, and Speedy” (PLUS) deployment of SAI, giving the US and China a pivotal role in determining whether and how SAI is implemented.

The history of SRM governance 

This review by Jinnah and Dove covers the history of SRM governance and political milestones from 2006 to 2024. They highlight and explain key developments, identify gaps in governance, and discuss possible future trajectories.

MCB could impact stratospheric ozone 

It is widely recognised that SAI could impact the recovery of the ozone layer. Bednarz et al. find that MCB could also have significant effects on stratospheric ozone. Despite being deployed far from the stratosphere, MCB would produce changes to atmospheric temperatures and circulation that would impact ozone levels.

An effective MCB trial 

Hernandez-Jaramillo et al. present results from their MCB trial in Australia. They found that artificially generated sea-salt aerosols from their research vessel were able to reach the cloud base and change cloud properties. 

Community and Events

Participants at the Africa Climate Intervention Research Hub meeting in Cape Town, South Africa – 8 May 2025. Photo Credit: ACIRH

A new hub for SRM research in Africa 

The Degrees Global Forum in Cape Town brought together 330 scientists, policymakers and NGO representatives from around the world, including over half from the Global South. The Africa Climate Intervention Research Hub launched at the event – a new initiative that aims to support researchers and build a knowledge base in Africa to inform policy discussions on specific regional impacts. 

Making the case for African leadership on SRM 

Hands Off Mother Earth claimed the Degrees Global Forum was an “effort to co-opt the African climate movement”, but African SRM researchers responded, arguing that “Calls to halt research under the banner of ‘anti-colonialism’ risk replicating colonial dynamics...". These researchers stressed: “We are not advocating for the deployment of SRM technologies. Instead, we are investigating what SRM could mean for Africa.” This exchange follows a recent op-ed by Saliem Fakir and Shuchi Talati on Why African Leadership Matters in Geoengineering (Project Syndicate). 

British perspectives on geoengineering 

A new survey by YouGov explores public willingness to support geoengineering projects in the UK. Britons responded that more dramatic action is needed on climate change, but prefer to try to reduce consumption than use technological solutions. Younger audiences were most supportive of geoengineering techniques, whilst also being the most likely to say they are concerned about climate change as an issue. 

Funding opportunity: Reflective 

Reflective are releasing their first funding opportunity: Impacts and Tradeoffs of Simulated High-Latitude/Low-Altitude SAI Deployment. Submission deadline for proposals: 9 June.  

CSEi receives $5 million grant from Quadrature Climate Foundation to advance SRM research 

The three-year grant aims to reduce uncertainties surrounding the scientific, engineering, and economic practicalities of sulphate aerosol-based SRM.

In the Media

Getty Images. Credit: Nuthawut Somsuk

Follow the money 

Our new funding dataset was picked up by The Economist, which reported that Britain is now the biggest funder of solar-geoengineering research. Some outlets focused on what the new funding meant for the UK, and explained what they are and are not studying (Carbon Brief), while others highlighted wider trends (Bloomberg) and the gap between funding in the Global North vs. Global South (E&E Politico). 

SRM field experiments planned for the UK 

ARIA’s announcement of the funding of outdoor experiments led to global media coverage of what solar geoengineering is (The Telegraph), and speculation as to how it might affect weather – leading to some stories that centred on ‘dimming the sun’ (The Times), conspiracy theories (Metro UK), and sci-fi films (Newsweek). 

EPA Letter to Make Sunsets 

The US Environmental Protection Agency (EPA) submitted an information demand to “Make Sunsets”, suggesting they may take action (WLT Report). The news broke as the EPA also rolled back regulations for large polluters (Inside Climate News). Make Sunsets have now responded to the EPA. 

Could SAI be feasible with current technology? 

The study by Duffey et al. captured journalists’ imagination – that geoengineering could use existing aircraft (Phys.org) such as Boeing 777s (The Telegraph). 

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