NOAA tests stratospheric particles

Posts on X on Tuesday framed NOAA as actively testing particle releases in the stratosphere and over marine clouds to cool the planet. NOAA’s public materials support the underlying science being discussed, but they do not show a verified NOAA announcement that the agency has begun the kind of operational climate-intervention tests described in those posts. NOAA research pages, laboratory summaries and Federal Register notices show an agency studying stratospheric aerosol injection and marine cloud brightening, publishing model results, and discussing how such experiments should be reported and evaluated. NOAA’s own language distinguishes between two approaches. A March 24, 2025 NOAA Research article said stratospheric aerosol injection, or SAI, would disperse microscopic particles 7 to 30 miles high to reflect some sunlight, while marine cloud brightening, or MCB, would seed low marine clouds with sea-salt particles to make them more reflective. ### Did NOAA say it is already releasing particles to cool Earth? (research.noaa.gov) NOAA’s public pages I found do not say that. The clearest NOAA materials available are research summaries, not deployment notices. A September 20, 2024 Federal Register notice showed NOAA asking for public comment on whether its weather-modification reporting rules should be updated to account for solar-radiation-modification experiments, and it said NOAA was taking “no position at this time regarding the merits” of the petition. (research.noaa.gov) That matters because the social posts describe a live test program with timelines through 2027 and deployments over Pacific marine zones. I did not find a NOAA release, project page or Federal Register filing confirming those specific claims. The available NOAA sources support ongoing research and measurement work, but not a verified announcement of a 2026 field deployment to cool Earth. (federalregister.gov) ### What did NOAA researchers actually publish on stratospheric particles? A 2025 NOAA-backed paper and agency summary described a modeling result, not a field release announcement. NOAA said the study found that sunlight diffused by stratospheric particles could indirectly make marine clouds below more reflective. Lead author Jake Gristey said the effect could increase sunlight reflection from a cloud by as much as 10%. (pmel.noaa.gov) The paper described what the authors called “diffusion-brightening.” In NOAA’s repository summary, the researchers said idealized calculations suggested clouds could reflect about 10% more incoming sunlight under some conditions, and that the radiative effect could exceed direct stratospheric aerosol reflection in many cloudy scenes. ### What is marine cloud brightening in NOAA’s work? NOAA’s Pacific Marine Environmental Laboratory described MCB in March 2024 as injecting salt spray into shallow marine clouds to brighten them and reduce heat absorbed by the water below. (research.noaa.gov) That page said 31 atmospheric scientists, including PMEL chemist Patricia Quinn, published a research roadmap calling for laboratory work, field experiments, monitoring and modeling before policymakers consider whether MCB should be deployed. (repository.library.noaa.gov) Graham Feingold of NOAA’s Chemical Sciences Laboratory said in that NOAA summary that policymakers do not yet have the information needed to decide “if and when MCB should be deployed.” That wording points to an earlier research stage than the social posts suggest. ### Are there NOAA field programs over the Pacific tied to this science? NOAA does have Pacific measurement programs related to aerosols, clouds and radiation. (pmel.noaa.gov) PMEL said its 2024 uncrewed aircraft flights from Vandenberg Space Force Base measured aerosol, cloud and radiative properties over central California coastal waters, up to 25 nautical miles from shore, to assess processes relevant to marine cloud brightening. Those flights were observation missions. (pmel.noaa.gov) PMEL’s page described payloads measuring vertical profiles and said the work advanced a longer-term goal of routine long-endurance flights from NOAA ships. The page did not describe deliberate climate-cooling releases into marine clouds. ### Why are scientists cautious even in NOAA’s own summaries? NOAA’s prior studies describe large uncertainties and possible side effects. A 2021 NOAA Research article said studies of ship-track clouds may have overestimated cooling effects by up to 200%. (pmel.noaa.gov) Another 2021 NOAA summary said particle size and number are critical, and that poorly chosen particles could produce little brightening or even less reflective clouds. A May 14, 2025 NOAA Chemical Sciences Laboratory summary added that marine cloud brightening could affect the stratosphere and ozone layer, with lead author Ewa Bednarz saying the effects could reach into the stratosphere. The next concrete places to look are NOAA Research, PMEL and the Federal Register docket NOAA-OAR-2024-0091, which document published studies, field measurements and reporting-rule discussions rather than a confirmed 2026 deployment notice. (research.noaa.gov) (pmel.noaa.gov) (csl.noaa.gov)