Has the U.S. government approved any field experiments for solar radiation management since 2020?

1. Federal posture: “not engaged in outdoor testing”

Key U.S. agencies and government pages state plainly that the federal government is not carrying out outdoor SRM field tests: EPA’s public pages say the U.S. government “is not engaged in any form of outdoor testing (e.g., small‑scale experiments designed to study injection technologies) or large‑scale deployment” and that federal research focuses on observation, modeling and monitoring ^[1]. EPA’s frequent‑questions page repeats that federal agencies are not engaged in outdoor SRM testing and notes awareness of only limited private actor activity ^[5].

2. Congressional and OSTP activity has opened research, not field releases

Congressional direction and White House reports have increased federal attention to solar geoengineering as an area for research, governance and coordination — for example, mandates to OSTP, NOAA, DOE and NSF to prepare plans and assessments — but those documents and proposals emphasize assessment, governance and modeling rather than authorizing field release experiments by government agencies ^{[6] [7]}.

3. University and private experiments — not the same as federal approval

Since 2020, several non‑federal projects have sought to run small field tests. Marine cloud brightening work led by Daniel Harrison began tests in March 2020 (not a federal program) and other academic projects (notably Harvard’s SCoPEx planning) have attempted or paused balloon and flight tests amid logistical, ethical and regulatory pushback ^{[2] [8]}. Reporting describes these as university or private efforts, often delayed, canceled, or contested by local officials and Indigenous groups — not approvals by the U.S. government ^{[2] [8]}.

4. Private commercial actions created policy backlash

Private actors have taken independent steps that attracted government scrutiny and international reaction. For example, the startup “Make Sunsets” reportedly released small quantities of sulfur dioxide on balloons, prompting EPA inquiries and Mexico’s 2023 prohibition on experiments after unauthorized U.S. launches ^{[1] [9]}. EPA has indicated it is tracking such private activity but distinguishes it from federal authorization ^[1].

5. Field tests are rare, contested and often halted by non‑federal authorities

Multiple sources note that attempts to run small SRM field tests since 2020 have repeatedly failed, been delayed, or drawn significant opposition. A University of Washington marine cloud brightening experiment was halted or canceled by local officials; several SCoPEx launch attempts failed and were paused; other marine and stratospheric tests have been postponed amid public concern ^{[2] [3] [10]}. Science writers report that field trials remain scarce despite some groups calling for small‑scale experiments ^{[11] [12]}.

6. What the sources don’t say — limits of the public record

Available sources do not mention any formal federal approval process that has authorized a U.S. government agency to perform outdoor SRM releases since 2020; they do not document a signed federal permit or directive authorizing federal field experiments ^{[1] [5]}. Sources likewise do not provide an exhaustive audit of every local permit or classified action; they focus on public statements, agency pages, media investigations and academic reporting ^{[1] [10]}.

7. Competing perspectives and the politics beneath the headlines

Advocates for limited, small‑scale field experiments argue they are necessary to reduce scientific uncertainty and inform governance ^{[11] [8]}. Critics and many governments and civil society actors argue experiments risk normalizing deployment, produce geopolitical risks, and should be moratoria‑bound until governance is agreed ^{[11] [12]}. The federal posture — funding assessments and governance frameworks while publicly disavowing outdoor testing — reflects a cautious middle ground driven by scientific, ethical and political pressures ^{[6] [1]}.

Bottom line: public federal records and agency statements reviewed here show no U.S. government‑approved SRM field experiments since 2020; activity in that period has been driven by universities, private actors and foreign funders, and has repeatedly run into regulatory, political and public opposition ^{[1] [2] [3]}.