The U.S. Is Building an Early Warning System to Detect Geoengineering

Every few weeks, researchers in Boulder, Colo., release a balloon that rises 17 miles into the sky. Similar balloons are launched with less frequency from sites in Alaska, Hawaii and New Zealand; Reunion Island, near the coast of Africa; and even Antarctica. They make up the building blocks of a system that would alert American scientists to geoengineering.

https://www.nytimes.com/2024/11/28/climate/geoengineering-early-warning-system.html