Weather modification involves seeding clouds with grains of dry ice (solid carbon dioxide) or tiny particles of silver iodide to stimulate rainfall. The most common form of weather modification is cloud seeding to increase rain or snow, usually for the purpose of increasing the local water supply.

If large-scale weather control were to become feasible, potential negative implications may include unintended side effects (especially given the chaotic nature of weather development), damage to existing ecosystems, health risks to humans, malevolent control or use as a weapon, ELF hot spots causing slightly accelerated ionospheric depletion by solar wind and many more. Silver iodide can cause temporary incapacitation or possible residual injury to humans and mammals with intense or continued but not chronic exposure.

Operated by the Air Force Research Laboratory’s Space Vehicles Directorate, HAARP constitutes a system of powerful antennas capable of creating “controlled local modifications of the ionosphere. HAARP could contribute to climate change by intensively bombarding the atmosphere with high-frequency rays. Returning low-frequency waves at high intensity could also affect people’s brains, and effects on tectonic movements cannot be ruled out.