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March 2025 Update

Dear ,

The biggest news this month: the Intergovernmental Panel on Climate Change (IPCC) will cover SRM in some of the chapters of its next assessment report. We asked experts for their reactions on the Climate Reflections podcast.

Also featured: debate around ARIA's funding of SRM field experiments, two engaging perspectives – Beth Chalecki addresses the role of sovereignty in SRM and Sandro Vattioni discusses alternative particles that could be used in stratospheric aerosol injection (SAI) – and an insightful podcast conversation on governance with Cynthia Scharf.

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-The SRM360 Team

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New From SRM360

In Conversation

In a contentious meeting in late February, the IPCC agreed on outlines that include discussions of SRM for its 7th assessment report. For the first time in IPCC history, the US was notably absent, having been banned from participation by the Trump administration. In our news roundup, Pete Irvine discusses these and other recent SRM-relevant developments with experts.

Listen at srm360.org or on your preferred podcast platform.

SRM Academic Highlights

Getty Images. Credit: Matt Dutcher

Alternatives to sulphur dioxide for SAI 

Vattioni et al. explore the side effects of SAI using solid alumina or calcite particles. Using solid particles for SAI instead of sulphur dioxide could lead to less stratospheric warming and haziness, but uncertainties remain about ozone layer impacts.

Optimizing marine cloud brightening 

Using computer simulations, Song et al. evaluated marine cloud brightening (MCB) effectiveness when focused in different areas and using different sea-salt spraying strategies. Their study provides insights into regions’ sensitivity to MCB and optimal injection amounts.

SAI cooperation benefits competitors 

China and the US are “great power competitors” with implications for SAI policy and national security. By analysing 4 policy scenarios, Jeffrey Nielsen found the US and China could benefit by cooperating on SAI, and that expanding SAI research and conventional mitigation could be win-win options.

Profit-driven SRM is a risky strategy 

A new study by Surprise et al. argues that for-profit SRM is a logical outgrowth of market-driven climate policy and makes the case for explicit efforts to curb commercial SRM actors.

SAI’s impact on malaria 

Hussain et al. investigated how SAI would affect the transmission of malaria in South Asia. They found that the lower temperatures under SAI would decrease the rate of transmission, especially in India and Bangladesh.

Community and Events

Credit: IISD/ENB | Anastasia Rodopoulou

SRM to feature in next IPCC report

The IPCC agreed an outline for its next assessment report that includes limited and carefully framed coverage of SRM, emphasising uncertainties, risks, and ethical dimensions.

The summary report of the latest meeting shows that support for including SRM came from participants who believed the IPCC should provide a full, science-based assessment of all proposed climate-response options – even speculative ones – so that policymakers see both potential effects and major uncertainties: IPCC report timeline still undecided after ‘most difficult’ meeting in China (Carbon Brief).

Rapidly approaching a flashpoint? 

In a new article, Shuchi Talati and Whitney Peterson argue that rapid changes and uncertainty in the Trump administration in the US are leading to volatility and polarisation that could undermine the ability to have informed and inclusive discussions about SRM and its governance.

SRM researchers share their stories 

Familiar faces from the SRM community have recently taken to the ‘red dot’ stage of TedX to share their views: Later is too late, we urgently need research on sunlight reflection (Dakota Gruener), Lessons from the Arctic teach us we need a new definition of "conservation" (Brad Ack), Restoring the Arctic is restoring hope and demands collaborative action (Kerry Nickols).

Will the US explore SRM as an emergency measure? 

Hugh Hunt and Shaun Fitzgerald argue that geoengineering (or “climate repair”) remains politically divisive but could gain momentum under a second Trump presidency, as more extreme weather events are experienced: Geoengineering is politically off-limits—could a Trump presidency change that? (The Conversation).

Engaging stakeholders on SRM 

A recent discussion of the European SRM landscape highlighted the need to identify knowledge gaps and solicit feedback from diverse stakeholders to co-create guidelines and principles governing future research: Co-CREATE Seminar: Towards a European Blueprint for Responsible SRM Research (Climate Strategies).

In the Media

Getty Images. Credit: da-kuk

US climate science under threat 

Donald Trump’s cuts to climate science funding continue, with NOAA in the spotlight: The state of Trump’s climate blitz (Politico), NOAA firings hit the birthplace of weather and climate forecasting (Science).

Scientists have pushed back, with a petition from the Union of Concerned Scientists, protests and attempts to conserve research data: US scientists rebuild climate risk map deleted from government site (NewScientist), US science is under threat ― now scientists are fighting back (Nature News).

Proposed state legislation on SRM growing 

US states continue to explore bans on SRM: Proposed 'weather control' bans surge across US states (Phys.org), Utah senators tackle solar geoengineering (Newsy-Today), Bills on elections, immigration and guns squeak past Legislature’s ‘funnel’ deadline (Albia News).

ARIA funding of field trials faces criticism  

Raymond Pierrehumbert and Michael Mann wrote an opinion piece for The Guardian on plans by the UK’s Advanced Research and Invention Agency (ARIA) to fund SRM research, including outdoor experiments. They claimed there was “extreme danger in launching such field trials into an environment with neither national nor international governance in place”.

Matthew Henry and Stuart Haszeldine responded: “The risks of solar geoengineering must be balanced with the risks from the warming that would be attenuated”.

Should the World Bank be thinking about SRM?  

A recent article explores SRM as a potential option for responding to climate change, highlighting interdisciplinary collaboration, particularly involving economics, as important: Beyond Blue Sky Research (World Bank Blogs).

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